Question 1

GRP Flat Roof Explained: Fibreglass vs Felt

Accepted Answer

A GRP flat roof is a flat roofing system built from glass reinforced plastic, the same fibreglass laminate used on boat hulls. Layers of catalysed resin and chopped-strand glass matting are laid over a conditioned timber deck and cure into one solid, jointless waterproof shell. Because there are no joints or laps to fail, a well-installed fibreglass flat roof commonly lasts 25 to 30 years or more, which is why it has largely replaced traditional felt on domestic extensions, dormers, porches and garages.

What is a GRP flat roof made of?
GRP stands for glass reinforced plastic. On a flat roof it is built up in stages rather than rolled out like a sheet material. The result is a rigid, jointless surface bonded to the deck below.

The deck. A GRP roof needs a stable, dry base, usually 18mm exterior-grade OSB3 boarding fixed to the joists. Movement in the deck is the enemy of any fibreglass laminate, so the boarding and fixings matter as much as the resin.
Trims. GRP edge, drip and gutter trims are bonded around the perimeter to form clean edges and shed water where you want it.
The laminate. Catalysed resin is applied and glass matting is worked into it to remove air, then a coloured topcoat resin seals the surface.
The topcoat. This is the visible, UV-stable finish, typically dark or light grey, that gives the roof its durability and appearance.

We stock complete GRP systems and the individual components on our flat roofing products range, so roofers can pick up resin, matting, topcoat and matching trims from one counter.
GRP vs felt vs EPDM: how they compare
Felt (torch-on built-up felt) and EPDM rubber are the two systems most people weigh a fibreglass flat roof against. Each has a place, and the right choice depends on the deck, the shape of the roof and how long you want it to last.

Feature
GRP fibreglass
Torch-on felt
EPDM rubber

Typical lifespan
25 to 30-plus years
10 to 20 years
30 to 40 years

Finish
Jointless, rigid, walk-on
Layered sheets with laps
Single flexible membrane

Joints and seams
None once cured
Multiple lapped joints
Few, but glued/taped seams

Install conditions
Dry weather only, temperature-sensitive
Naked flame (heat/fire risk)
Adhesive-based, dry preferred

Best suited to
Complex shapes, upstands, foot traffic
Budget jobs, simple decks
Large simple areas

The headline difference in the GRP vs felt flat roof question is the seams. Felt is laid in overlapping layers that are bonded with heat, and those laps are the first thing to lift, split or let water in as the roof ages. A GRP roof cures into a single continuous skin with nothing to peel back, so it copes well with the detailing around parapets, pipe penetrations and rooflights where felt tends to fail first. EPDM rubber is a strong, long-lived alternative, but it is a flexible membrane rather than a hard shell, so GRP is usually the pick where the surface needs to take regular foot traffic or a walk-on finish.
How long does a GRP flat roof last?
GRP roof lifespan is one of its biggest selling points. A correctly specified and installed fibreglass roof will typically give 25 to 30 years of service, and many go well beyond 30 with little measurable deterioration. Most GRP systems carry a manufacturer guarantee of around 20 years or more when fitted to the system specification. The topcoat is UV-stable, so unlike felt it does not dry out and crack in the sun, and there are no laps to work loose. Basic upkeep is light: keep gutters and outlets clear, and check the surface every few years.
Why installation temperature and dry weather matter
The one real constraint with fibreglass roofing is that it is a wet-lay chemical process, so the weather has to cooperate. The resin cures through a reaction started by a catalyst, and that reaction is temperature-dependent.

It must be dry. The deck has to be completely dry before work starts, and no rain can fall while the resin is going off. Moisture trapped under the laminate causes blistering and poor adhesion.
Temperature range. As a rule GRP is laid above about 5&deg;C and out of very hot sun. Too cold and the resin will not cure properly; too hot and it goes off before it can be worked. Installers adjust the catalyst ratio to suit the day&#8217;s temperature.
Curing times. A topcoat is usually touch-dry within roughly an hour, but full cure takes longer, up to a couple of days, and foot traffic should wait around 24 hours in mild conditions.

In practice this means GRP is a spring-to-autumn job in most of Kent, Surrey and Sussex, or a dry, mild spell in winter. It is worth planning around, because rushing a fibreglass roof in the wrong conditions is the most common cause of early failure.
What affects the cost of a GRP flat roof?
We supply materials rather than quote fixed installed prices, and any honest answer on a GRP flat roof cost depends on the specifics of the job. The main factors are straightforward:

Roof area. More square metres means more boarding, resin, matting and topcoat, plus more labour time.
Deck condition. A tired deck that needs stripping and re-boarding adds material and labour. GRP needs a sound, dry base to bond to.
Trims and detailing. The number of edges, upstands, corners, outlets and pipe penetrations drives how much trim and hand-detailing is involved.
Access and labour. Height, scaffolding and how easily the deck can be reached all feed into the day rate.

For a homeowner trying to sanity-check quotes, it helps to look at a national reference for typical UK flat roof replacement costs before comparing installers. If you are pricing the materials for a job, our team can put a supply list together against your measurements. You can get a quote on GRP systems and trims, and we will help you specify the right resin quantities for the area and the weather.
Is a fibreglass roof the right choice for you?
GRP tends to be the strongest option for extensions, dormers, bay roofs, balconies and any flat area that needs a hard, walk-on, joint-free finish and a long life. Felt still makes sense on tight budgets or simple sheds, and EPDM suits large, plain areas. Where a GRP roof earns its keep is on the fiddly roofs with lots of detail, the ones where a seam would eventually be the weak point.
Brian Gow Roofing Supplies has been supplying flat roofing materials to trade and homeowners across Sussex, Kent and Surrey since 1996, so if you are unsure which system fits your roof, ask. You can see the full flat roofing range, or call in and see the systems in person at our main Haywards Heath roofing supplies depot at Scaynes Hill. Bring your measurements and we will help you get the specification and the quantities right first time.
Frequently asked questions
What is a GRP flat roof?
A GRP flat roof is a flat roofing system made from glass reinforced plastic, or fibreglass. Catalysed resin and glass matting are laid over a dry timber deck and cure into one solid, jointless waterproof shell. Because it has no joints or laps to fail, it is a durable, walk-on finish suited to extensions, dormers, garages and balconies.
Is GRP better than felt for a flat roof?
For most jobs, yes. A GRP roof cures into a single continuous skin, while felt is laid in overlapping layers whose laps tend to lift and split as they age. GRP typically lasts 25 to 30 years against felt&#8217;s 10 to 20, and copes better with detailing around upstands and penetrations. Felt still suits simple, budget-led roofs.
How long does a GRP flat roof last?
A correctly installed GRP flat roof usually lasts 25 to 30 years, and many go beyond 30 with little deterioration. Most systems carry a manufacturer guarantee of around 20 years or more when fitted to specification. The UV-stable topcoat resists cracking in the sun, and with no seams to work loose, upkeep is limited to clearing gutters and outlets.
Can you install a GRP roof in winter?
You can, but only in the right conditions. GRP must be laid on a completely dry deck with no rain during curing, and generally above about 5&deg;C. In cold weather the resin will not cure properly, so winter work needs a dry, mild spell and a catalyst ratio matched to the temperature. In practice most GRP roofs go on between spring and autumn.
What affects the cost of a GRP flat roof?
The main factors are roof area, the condition of the existing deck, and the amount of trim and detailing around edges, upstands and penetrations. Access, height and scaffolding affect labour. A larger roof or one needing a fresh deck uses more material and time. We supply the systems and can price materials against your measurements.
Is a fibreglass roof any good?
A fibreglass roof is one of the most durable domestic flat roofing options available. Its jointless, rigid finish handles foot traffic and complex shapes well, resists UV without cracking, and commonly lasts 25 to 30 years or more. The main trade-off is installation: it needs dry weather and the right temperature to cure, so it is not a wet-day job.

Question 2

Lead Flashing Codes Explained: Code 3 to Code 8

Accepted Answer

A lead flashing code tells you how thick a piece of rolled lead sheet is. The codes run from Code 3 (the thinnest, 1.32mm) up to Code 8 (the thickest, 3.55mm), and the higher the number, the thicker and heavier the lead. Each code is made to BS EN 12588 and carries a standard colour marking on the roll, so Code 3 is green, Code 4 is blue and Code 5 is red. For most domestic flashing work you want Code 4; step up to Code 5 or Code 6 for gutters, valleys and exposed positions.

What do lead codes actually mean?
Lead for roofing is sold by code rather than by a plain thickness figure, and the system is a hangover from the old imperial method of describing lead by its weight per square foot. A Code 4 sheet, for example, once weighed roughly four pounds per square foot. The trade kept the numbers even after the switch to metric, and rolled lead sheet is now manufactured to the European standard BS EN 12588, which fixes the thickness and weight for each code.
The important thing on site is simple: a higher code means thicker lead. Thicker lead lasts longer and stands up better to exposure, but it also costs more and is heavier to dress and lift. Picking the right code is a balance between the job it has to do and not paying for more metal than you need.
Lead flashing code chart: colour, thickness and use
Every roll of lead is identified by a colour-coded stripe or label so you can tell the codes apart at a glance in the yard or on the roof. The table below lists the code, its colour marking, the thickness in millimetres to BS EN 12588, and where each one is typically used.

Lead code
Colour marking
Thickness (mm)
Typical use

Code 3
Green
1.32
Soakers, light repair flashings, straps where loading is minimal

Code 4
Blue
1.80
Apron, step and chimney flashings, abutments on tile and slate. The standard code for most domestic flashing

Code 5
Red
2.24
Heavier flashings, back gutters, wider aprons and more exposed sites

Code 6
Black
2.65
Valleys, parapet and box gutters, dormer cheeks, larger bays

Code 7
White
3.15
Heavy-duty gutters, high-exposure detailing and lead cladding

Code 8
Orange
3.55
The heaviest cladding, roofing and specialist or ornamental leadwork

Which lead code for flashing?
For the everyday flashing jobs most roofers meet, Code 4 lead is the workhorse. It suits chimney flashings, apron flashings, step flashings and abutments where a pitched roof meets a wall, and it is what you will fit on the majority of houses across Sussex and Kent. It dresses cleanly, sits well against brick and tile, and gives a long service life without being needlessly heavy.
Where the lead has to carry water rather than just shed it, move up the codes. Back gutters behind chimneys, valley gutters, box and parapet gutters, and larger lead bays all take more punishment from standing water, foot traffic and thermal movement, so Code 5 or Code 6 lead is the sensible choice. Code 5 lead is the usual step up from Code 4 for gutters and exposed flashings, while Code 6 and above come into their own on valleys, cladding and heritage work.
Code 4 versus Code 5: how to choose
The jump from Code 4 to Code 5 is the decision that comes up most often. Code 4 (1.80mm) is right for standard flashings and soakers; Code 5 (2.24mm) is the better call for anything holding water, anything in a sheltered valley that stays damp, or anywhere the lead is wide, long or exposed to strong wind. Building specifications and the Lead Sheet Association&#8217;s guidance often set minimum codes for particular details, so if the job has been designed, follow what the drawings ask for. If you are unsure, our counter staff have been sizing lead for these jobs since 1996 and can tell you what fits the detail. See our lead and lead accessories range for the codes we keep in stock.
How is rolled lead sold?
Rolled lead sheet is sold by the roll, cut to a range of standard widths and supplied in set lengths, most commonly 3 metre and 6 metre rolls. You order it by code first, then by the width you need for the detail. A narrow roll suits step and cover flashings, while wider rolls are used for gutters, valleys and bays. Because lead is heavy, price and delivery are worked out by weight, which is why the weight per square metre climbs steadily as the code goes up.
We stock the common codes and widths across our depots and can advise on quantities so you are not left short or paying for offcuts. We also stock the fixings and accessories that go with it, so you can pick up everything for the detail in one visit. Trade and homeowners can collect from any branch, including our Hailsham roofing supplies depot, or take delivery across the South East.
A note on getting the code right
Fitting a code that is too thin is a false economy. Thin lead on a wide gutter or an exposed flashing works harder, fatigues faster and can split at the folds, which means water in the building and a return visit. Going too thick wastes money and makes the lead harder to dress. Matching the code to the detail, then lapping and clipping it correctly, is what gives lead its reputation for lasting decades. If you tell us the job, we will tell you the code.
Need lead for a job on the books? Get a quote or call your nearest depot and we will confirm the right code, width and length for the detail.
Frequently asked questions
What do lead flashing codes mean?
Lead flashing codes describe the thickness of rolled lead sheet. They run from Code 3 to Code 8, and a higher number means thicker, heavier lead. The system comes from the old imperial weight of lead per square foot, but the codes and their exact thicknesses are now set by the standard BS EN 12588.
What is the difference between Code 4 and Code 5 lead?
Code 4 lead is 1.80mm thick and is the standard choice for most flashings, such as chimney, apron and step flashings. Code 5 lead is thicker at 2.24mm and heavier, so it is better for back gutters, valleys, wider aprons and more exposed positions where the lead has to carry water or take more wear.
What is the colour code for lead flashing?
Each lead code has a colour marking on the roll so you can identify it: Code 3 is green, Code 4 is blue, Code 5 is red, Code 6 is black, Code 7 is white and Code 8 is orange. The stripe or label lets you tell the codes apart quickly on site without measuring the thickness.
What thickness is Code 4 lead?
Code 4 lead is 1.80mm thick under BS EN 12588, weighing about 20.41kg per square metre. It is the most widely used code for domestic flashings, including chimney flashings, apron flashings, step flashings and abutments where a pitched roof meets a wall.
Which lead code should I use for flashing?
For standard flashings on houses, Code 4 lead is the usual choice. Use Code 3 for soakers and light work, and step up to Code 5 or Code 6 for back gutters, valleys, wider bays and exposed sites. If the job has been specified or drawn, follow the code the specification calls for.
How is rolled lead sold?
Rolled lead sheet is sold by the roll, ordered by code and then by width, and usually supplied in 3 metre or 6 metre lengths. Because lead is heavy, it is priced and delivered by weight, so the cost rises as the code and thickness increase. Merchants stock a range of widths to suit different flashing and gutter details.

Question 3

Dry Verge Systems Explained

Accepted Answer

A dry verge system is a set of mechanically fixed caps, or units, that clip and screw along the gable edge of a pitched roof in place of bedded mortar. Each unit locks over the edge tile and the outer batten, sealing the verge against wind, rain and pests while holding the perimeter tiles down. Because the caps are fixed with screws or clips rather than relying on mortar, they will not crack or wash out, and they need almost no maintenance for the life of the roof.

What is a dry verge system?
The verge is the sloping edge of a roof at each gable end, where the tiles overhang the wall. For decades this edge was finished with a bed of sand and cement mortar, sometimes with an undercloak below it. A dry verge does the same job without any wet trade. A row of interlocking plastic units runs up the verge, one per tile course, each one clipping over the tile and screwing down into the batten below.
The units come as a kit: verge caps for the main run, a ridge end cap to close the top, and an eaves closure at the bottom. Most modern systems are &#8220;universal&#8221;, meaning one profile suits a range of concrete and clay tile shapes, so you rarely need a tile-specific part. This is the same family of products as dry ridge and dry hip, and together they are known as dry fix roofing.
You will hear it called dry verge, dry-fix verge or mechanically fixed verge. They all mean the same thing: the tile perimeter is held by a fixing you can point to, not by mortar that may or may not still be doing its job in twenty years.
Why dry verge is now the standard for new roofs
This is not just fashion. It follows a change in the British Standard for slating and tiling. BS 5534 was revised in 2014, and one of the headline changes was that bedding mortar no longer counts toward resisting wind uplift. In practice that means the tiles along a verge, ridge or hip have to be mechanically fixed. You can still use mortar for appearance, but it must be backed up by clips or a dry system, because on its own it no longer satisfies the standard.
A second standard, BS 8612, was published in 2018 to sit alongside it. It is the product specification for dry-fixed ridge, hip and verge systems, and it defines how these products should be tested for wind load and performance. Before BS 8612 there was no agreed test, so quality varied. Now a specifier can check that a dry verge has been tested to the right standard for the exposure of the site.
The upshot is simple. For new work and re-roofs, a dry verge system is effectively what is expected, because it is the straightforward way to meet the fixing requirements of BS 5534 at the gable. Our counter staff have been advising trade and homeowners on these fixing rules since well before the changes bedded in, and we stock verge to match the tiles we sell for pitched roofing.
Dry verge vs mortar
The dry verge vs mortar question comes up on almost every re-roof. Mortar is cheap on materials and looks traditional when fresh, but it is a wet trade that fails predictably at the edge of a roof. Here is how the two compare.

Point
Dry verge system
Mortar verge

Fixing
Mechanically screwed or clipped to the batten
Bedded in sand and cement, no mechanical hold on its own

Wind resistance
Tested to BS 8612; holds tiles down at the edge
Not counted toward wind uplift under BS 5534 since 2014

Cracking and repointing
None; will not crack or fall out
Cracks and drops out over years, needs repointing

Weather to install
Fitted in most conditions, no curing
Should not be laid in frost or heavy rain

Maintenance
Effectively none for the life of the roof
Ongoing inspection and repair

Pest and bird entry
Closes the verge gap
Gaps open up as mortar fails

Mortar still has its place on some conservation and heritage jobs where the look has to match exactly. For most work, though, a dry verge is the lower-maintenance and better-performing choice.
What colours do dry verge caps come in?
Dry verge caps are made in a small set of standard colours so they can be matched to the tile and the roofline. The four you will see most often are black, brown, grey (slate grey) and terracotta. Black and grey suit slate and dark concrete tiles, brown works with brown and buff tiles, and terracotta is chosen for clay and red concrete tiles. The plastic is UV-stabilised so the dry verge colours hold up in sunlight rather than fading quickly.
Because dry verge sits next to the fascia, bargeboard and guttering, it makes sense to pick the verge colour at the same time as the rest of the PVC roofline. Ask at the counter and we will help match the cap to the tile you are laying.
Can you fit dry verge to an existing roof?
Yes. Dry verge can be retrofitted to an existing roof, and it is a common upgrade when a mortar verge has started to crack and drop out. The old mortar is raked out and removed, the outer battens are checked and replaced if they are soft or too short, and the dry verge units are then screwed down course by course. It is a tidy job that does not need the whole roof stripped, and it usually costs less than repointing the verge every few years.
The one thing to check first is the batten. Dry verge needs sound timber to fix into, so if the battens at the gable are undersized or rotten they are replaced as part of the work. On a roof in reasonable condition, a retrofit dry verge gives you a maintenance-free edge without touching the field tiles.
Buying dry verge in Sussex, Kent and Surrey
We keep dry verge kits and the matching plastic roofline in stock across our depots, alongside the tiles they finish. Trade and homeowners can collect from the counter or have materials delivered across Sussex, Kent and Surrey from our main stock-holding depot at Haywards Heath. If you tell us the tile and the length of the verge, we will work out the units, ridge end caps and closures you need. Get a quote or call your nearest branch and we will sort it.
Frequently asked questions
What is a dry verge system?
A dry verge system is a run of interlocking plastic caps fixed along the gable edge of a pitched roof instead of mortar. Each unit clips over the edge tile and screws into the batten, sealing the verge and holding the perimeter tiles against wind, rain and pests without any wet trade.
Is dry verge better than mortar?
For most roofs, yes. Dry verge is mechanically fixed, so it will not crack or wash out like mortar, needs no repointing and meets the wind-fixing requirements of BS 5534. Mortar can still be used for a traditional look on heritage work, but it must be backed up by mechanical fixings.
Are dry verge systems any good?
They are the current standard for gable edges on new and re-roofed pitched roofs. Quality dry verge is tested to BS 8612 for wind performance, lasts the life of the roof and removes the ongoing maintenance a mortar verge needs. Buying a tested system from a proper merchant is what matters.
Do dry verge caps come in different colours?
Yes. Dry verge caps are usually made in black, brown, grey and terracotta so they can be matched to the tile and roofline. Black and grey suit slate and dark tiles, brown suits buff and brown tiles, and terracotta is chosen for clay and red concrete tiles.
Can you fit dry verge to an existing roof?
Yes. Dry verge is often retrofitted where a mortar verge has cracked. The old mortar is removed, the gable battens are checked and replaced if needed, and the units are screwed down course by course. It does not need the roof stripping and usually costs less than repeated repointing.
How are dry verge units fixed?
Each dry verge unit is mechanically fixed, screwed or clipped down onto the outer roofing batten, with each cap interlocking with the one below it. A ridge end cap closes the top of the run and an eaves closure finishes the bottom, giving a continuous, screwed-down edge rather than a bed of mortar.

Question 4

Clay vs Concrete Roof Tiles: Which Is Best?

Accepted Answer

The main difference between clay vs concrete roof tiles comes down to longevity, weight and colour. Clay roof tiles are fired from natural clay and routinely last 60 to 100 years or more, with the colour running right through the material so it never really fades. Concrete roof tiles are cheaper and heavier, typically last around 40 to 60 years, and their surface colour softens under UV over time. Concrete usually wins on upfront cost; clay wins on lifespan, weight and long-term looks, which is why it is so often the right choice on older and heritage properties.

Clay vs concrete roof tiles at a glance
Here is the head-to-head, so you can see where each material earns its place before we get into the detail.

Feature
Clay roof tiles
Concrete roof tiles

Typical lifespan
60 to 100+ years, often outlasting the roof structure
Around 40 to 60 years

Weight
Lighter per square metre on a like-for-like tile
Noticeably heavier; needs a stronger roof structure

Colour
Through-fired natural colour that holds for the life of the tile
Pigmented surface that can fade under UV over the years

Cost
Higher upfront material cost
Lower upfront material cost

Minimum pitch
Around 35&deg; for plain tiles; interlocking clay designs go lower
Interlocking profiles available down to low pitches

Best use
Period, listed and conservation properties; long-life new builds
Budget-conscious projects and large roof areas

Lifespan: do clay roofs last longer than concrete?
Yes. Clay is the more durable of the two by a clear margin. A well-laid clay roof commonly lasts between 60 and 100 years, and plenty of Sussex roofs are still weathertight well past the century mark. Concrete tiles generally give around 40 to 60 years of service. Most manufacturers guarantee both materials for roughly 30 years, so the extra life you get from clay is the difference between one re-roof in a lifetime and possibly two.
One point worth stressing: the tile is only half the story. The underlay, battens and fixings beneath it age too, and a clay roof will usually need its membrane and battens renewed long before the tiles themselves give out. That is why we advise trade and homeowners to specify quality throughout the whole system, not just the visible surface.
Weight and your roof structure
Concrete tiles are the heavier option, and that has real consequences. A concrete tile roof puts more load on the rafters, wall plates and walls, which matters if you are re-covering an older building that was originally built for lighter clay or slate. Swapping like for like is straightforward. Switching from clay to concrete on an old roof can mean a structural engineer needs to check the timbers first. Clay&#8217;s lighter weight is one reason it suits period properties, where the existing structure was never designed to carry modern concrete.
Colour: why concrete fades and clay does not
This is the difference most people notice from the pavement after fifteen or twenty years. Clay gets its colour from the natural clay itself, fired at high temperature so the colour is baked through the whole tile. It does not rely on a coating, so it holds its tone for the life of the roof and often mellows attractively rather than fading.
Concrete tiles are coloured with pigment, and while good tiles carry that pigment through the body as well as on the surface, the exposed face is what the weather attacks. Over time UV and rain soften the surface colour, and older concrete roofs can look patchy or washed out. Manufacturers use acrylic coatings and better pigments to slow this down, but a concrete tile will still shift more than a comparable clay one.
Cost: are clay roof tiles more expensive than concrete?
Generally yes, clay costs more per tile than concrete at the point of purchase. Concrete is the value option and is hard to beat on a tight budget or a large roof area. The picture changes when you look at the whole life of the roof. Because clay can last roughly twice as long, the cost spread over the years it serves can work out competitively, especially once you factor in the labour of a second re-roof. For an accurate figure on either material for your project, it is best to get a quote based on your actual roof area and tile choice.
Minimum roof pitch for clay tiles
Pitch decides which tiles you can even use. The minimum roof pitch for clay plain tiles is generally around 35 degrees, though some single-camber tiles can go down to about 30 degrees with an increased headlap, depending on the manufacturer. Interlocking clay tiles cope with shallower roofs, and certain proprietary designs with anti-capillary features are approved for pitches as low as the mid-teens, provided the manufacturer has the evidence to back it. Concrete interlocking profiles are also widely available for low pitches.
Whatever you choose, the fixing specification follows BS 5534, the British Standard for slating and tiling, which sets out how tiles must be laid and secured for your pitch and exposure. Always check the individual tile&#8217;s minimum pitch against the manufacturer&#8217;s data sheet rather than assuming. If you are unsure, our counter staff can match a tile to your pitch from our pitched roofing range.
Planning, listed buildings and conservation areas
On period, listed and conservation-area properties, clay is usually the sympathetic choice and is often what a conservation officer will expect to see. Handmade clay tiles in particular match the character and irregular texture of older Sussex and Kent roofs in a way concrete cannot. If your property is listed or sits in a conservation area, check with your local authority before you order, because the material and even the specific tile may be conditioned. Concrete is fine for most standard homes but rarely the right answer where heritage appearance matters.
How to tell clay from concrete tiles on your own roof
Not sure what you already have? Here is how to tell clay from concrete tiles without getting on the roof:

Colour and fading: an even, warm colour that has held up well points to clay. A grey, patchy or faded surface, especially with a slightly rough texture, usually means concrete.
Edges and finish: clay tiles have a smoother, sometimes glazed or sanded face and crisper edges. Concrete tends to look coarser, with a granular surface.
Weight and sound: a spare clay tile is lighter for its size and rings with a sharper note when tapped; concrete sounds duller.
Underside: if you can inspect a loose tile, clay is denser and more uniform through the body, while concrete looks like fine aggregate.

If you bring a sample tile into one of our depots, the team can identify it and match a replacement. Our Hailsham depot and our other branches across Sussex hold both clay and concrete, so matching an existing roof is usually straightforward.
Which should you choose?
If budget is the deciding factor, or you are covering a large modern roof, concrete is the sensible, dependable option. If you want the longest life, the lightest load on the structure, colour that lasts, or a tile that suits a period or conservation property, clay is worth the extra. We stock both, including Marley concrete tiles and handmade clay, so we can supply whichever fits your roof and your budget rather than pushing one over the other.
Talk to a merchant who knows tiles
Brian Gow Roofing Supplies has been supplying roofers, builders and homeowners across Kent, Surrey and Sussex since 1996. Bring us your pitch, your existing tile or your plans and we will help you specify the right material first time. Find your nearest depot, visit the counter, or get a quote to compare clay and concrete for your roof.
Frequently asked questions
What are the disadvantages of clay roof tiles?
The main drawbacks are cost and pitch. Clay tiles cost more per tile than concrete, so the upfront material bill is higher. Plain clay tiles also need a steeper roof, generally around 35 degrees, so they do not suit every low-pitch roof. Older or poor-quality clay tiles can also be more prone to frost damage, though modern clay is fired to resist it.
Are concrete roof tiles better than clay?
Concrete is better on two counts: price and low-pitch flexibility. It costs less per tile and interlocking profiles suit shallower roofs. Clay wins on lifespan, weight and colour retention, and is the stronger choice for period and conservation properties. Neither is simply better; the right answer depends on your budget, roof structure, pitch and whether appearance and longevity matter most.
How do I know if I have clay or concrete roof tiles?
Look at colour, texture and weight. Clay holds an even, warm colour and has a smoother, denser face with crisp edges. Concrete looks coarser and greyer and often fades or goes patchy with age. A spare clay tile is lighter and rings sharply when tapped, while concrete sounds dull. Bring a loose tile into one of our depots and we will identify it for you.
Do clay roofs last longer than concrete?
Yes. Clay roof tiles commonly last 60 to 100 years or more, while concrete tiles typically give around 40 to 60 years. Both are usually guaranteed for about 30 years by the manufacturer. Bear in mind the underlay, battens and fixings underneath will normally need renewing before good clay tiles wear out, so the whole system matters, not just the tile.
Are clay roof tiles more expensive than concrete?
Usually, yes. Clay costs more per tile than concrete at the point of purchase, which makes concrete the budget choice for large roofs. Over the life of the roof the gap narrows, because clay can last roughly twice as long and may save you a full re-roof. For an accurate comparison on your project, ask us for a quote on both materials.
What is the minimum roof pitch for clay tiles?
For clay plain tiles the minimum pitch is generally around 35 degrees, with some single-camber tiles going down to about 30 degrees. Interlocking clay tiles work on shallower roofs, and certain proprietary designs are approved for pitches into the mid-teens. Always check the specific tile&#8217;s data sheet, as fixing must follow BS 5534 for your pitch and exposure.

Question 5

Breathable Roofing Membrane vs Non-Breathable

Accepted Answer

A breathable roofing membrane is a lightweight underlay that sits beneath the tiles or slates and lets water vapour pass out of the roof space while keeping wind-driven rain and snow out. It replaces traditional bitumen felt as the secondary weather layer and, because it is vapour permeable, it reduces the risk of condensation building up on the underside of the roof. It does not, on its own, remove the need to design roof ventilation properly.

What a breathable roofing membrane actually does
The membrane is the second line of defence. The tiles or slates shed almost all the water, and the underlay catches anything that gets past them, wind-driven rain, dust and the odd bit of snow, then drains it down to the eaves. A modern breathable underlay is usually a triple-layer spun-bonded polypropylene sheet with a micro-porous film in the middle. That film is the clever part: it is watertight from the outside but open enough to let moisture vapour from inside the building escape outwards.
That matters because warm, moist air is always rising up through a house. If it hits a cold, sealed surface it condenses into water, and water sitting against roof timbers leads to rot, mould and rusting fixings over time. A breathable membrane gives that vapour a route out instead of trapping it. You will find these underlays across most pitched roofs we supply, and they sit alongside the tiles, battens and fixings on our pitched roofing materials range.
Breathable vs non-breathable membrane: roofing felt vs membrane
The old standard was bitumen felt, often called 1F felt. It is heavy, it is effectively vapour-impermeable, and it tends to sag between the rafters into a trough that can pool water. Because it does not let vapour through, any moisture rising from below condenses on its cold underside and stays there. In an insulated roof that is a recipe for interstitial condensation.
A breathable membrane is lighter, stronger and vapour open. It handles moisture in the opposite way, letting it pass through and away. Here is the short version.

Feature
Breathable membrane
Traditional bitumen felt (1F)

Vapour permeable
Yes, lets moisture out
No, effectively sealed

Weight
Light, easy to handle
Heavy

Sagging
Laid with light tension, minimal sag
Prone to sagging and pooling

Condensation risk
Lower, vapour escapes
Higher, vapour is trapped

Typical use today
Standard on most new pitched roofs
Occasional, some traditional specifications

Some roofers do still choose a heavier non-breathable or traditional felt on certain jobs, and there is nothing wrong with that where the design calls for it. The point is to match the underlay to the whole roof build-up, not to assume one type suits every situation.
Does a breathable membrane remove the need for roof ventilation?
This is the question that catches people out. The word &#8220;breathable&#8221; makes it sound as though the sheet handles all the moisture on its own. In practice, most breathable underlays still need the roof to be ventilated, and that ventilation has to be designed in line with BS 5250, the British Standard covering the management of moisture in buildings.
The reason is that membranes fall into two camps. Some are vapour permeable but still fairly airtight, and some are both vapour permeable and air open. Only an air-open, vapour-permeable membrane that carries specific BBA certification can potentially be used without additional roof-space ventilation, and even then the NHBC will only accept it on that basis where the certificate says so. A good example is that even a widely used underlay like Cromar&#8217;s Vent3 range, which is BBA certified, still carries manufacturer guidance recommending ventilation at the ridge in cold roof applications.
So the safe rule is simple: follow the membrane manufacturer&#8217;s instructions and its BBA certificate, and design the eaves and ridge ventilation to suit the roof. Do not treat the membrane as a substitute for that. If you are unsure which underlay pairs with which ventilation detail, our counter staff have been specifying this for years and are happy to talk it through.
Which side of a breathable membrane faces up, laps and lifespan
Orientation matters. The membrane has a printed or darker face that is laid facing upwards, towards the tiles, because that side gives better UV resistance. On a Cromar Vent3 Classic, for instance, that is the light grey printed side up. Fit it upside down and you compromise how it performs.
It is unrolled starting at the eaves and worked up the roof, so each higher course laps over the one below and water always runs onto the sheet rather than under it. Head laps and side laps should follow the manufacturer&#8217;s fixing instructions and NHBC guidance, with the lap size linked to the roof pitch and wind zone rather than a single fixed figure. Leave a drainage and ventilation gap of at least 25mm between the underlay and the tiles, and turn the membrane up at least 100mm behind any abutment flashing.
Lifespan is generous when it is fitted and covered correctly. A quality breathable underlay protected by the roof covering can last for several decades. The main thing that shortens it is UV exposure, so most membranes are only rated for a limited spell uncovered, commonly up to around three months, before the tiles or slates should go on. Get the covering on in good time and the underlay quietly does its job for the life of the roof.
Underlay and roofing materials across Sussex, Kent and Surrey
We have stocked breathable membranes, felts and the full pitched roofing kit since Brian Gow started the business back in 1996, and we carry Cromar underlays alongside our other brands. You can collect from any of our four depots or have materials delivered across the South East. If you are local, our Burgess Hill roofing supplies branch keeps membranes and underlay in stock, and you can find your nearest branch in a couple of clicks.
Not sure which underlay and ventilation setup your roof needs? Tell us the build-up and we will point you to the right membrane. Get a quote or call the yard and we will sort it.
Frequently asked questions
What is a breathable roofing membrane?
It is a lightweight underlay fitted beneath the tiles or slates as a secondary weather barrier. It keeps out wind-driven rain and snow while letting water vapour from inside the building pass out through the sheet. That vapour permeability lowers the risk of condensation forming on the roof timbers, which is why it has largely replaced traditional bitumen felt on pitched roofs.
What is the difference between a breathable and non-breathable membrane?
A breathable membrane lets water vapour escape from the roof space, while a non-breathable underlay such as bitumen felt seals it in. The breathable type is lighter, sags far less and reduces condensation risk. Non-breathable felt is heavier and can trap moisture against the timbers. Both keep rain out, but they manage internal moisture in opposite ways.
Do you still need roof ventilation with a breathable membrane?
Usually, yes. Most breathable membranes still need the roof ventilated in line with BS 5250, at the eaves and often the ridge. Only an air-open, vapour-permeable membrane with specific BBA certification can potentially be used without extra ventilation, and only where the certificate and NHBC allow it. Always follow the manufacturer&#8217;s instructions rather than assuming the membrane does it all.
Which side of a breathable membrane faces up?
The printed or darker side faces upwards, towards the tiles or slates. That face carries the better UV resistance and is the side the manufacturer designs to sit outermost. On a Cromar Vent3 Classic that is the light grey printed side up. Lay it the wrong way round and you reduce how well it performs, so check the roll before you start.
How long does a roofing membrane last?
A quality breathable membrane protected by the roof covering can last several decades, often the working life of the roof itself. The biggest threat is UV exposure while it is uncovered, so most are only rated for a limited period exposed, commonly up to about three months, before tiling. Correct fixing and avoiding damage during the build both help it reach full life.
Can you use a breathable membrane on any roof?
Breathable membranes suit most pitched tiled and slated roofs, in both warm and cold roof designs. They are not a primary waterproofing layer, so they always sit under a proper roof covering, and they are not intended for flat roofs, which need their own systems. The right choice depends on the roof pitch, the build-up and the ventilation, so check the membrane specification for your job.

Question 6

VELUX Window Sizes & Codes Explained (UK Size Chart)

Accepted Answer

VELUX window sizes are set by a short code that pairs a letter with a number: the letter is the width group and the number is the height group. So an MK04 is 78cm wide by 98cm high, and a UK04 is 134cm wide by the same 98cm high. Once you can read the code, you can match or replace any VELUX window without a tape measure in sight.

This guide covers the six standard width letters, the common height numbers, what the type code (GGL, GGU, GPL, GPU) tells you, where to find the code on the window itself, and how to measure if you are fitting from scratch. We have been supplying VELUX across Sussex, Kent and Surrey since 1996, so the questions below are the ones we answer at the trade counter most weeks.
How to read a VELUX size code
A VELUX size code is usually written as a letter, a middle letter, then two digits, for example MK04. It breaks down like this:

First letter (M) is the width group. Each letter maps to a fixed width in centimetres.
Middle letter (K) is the size range reference used across the current VELUX generation. Older windows may show the width letter and number without it, but the width and height still read the same way.
Two digits (04) are the height group, again a fixed measurement in centimetres.

So MK04 is M (78cm wide) and 04 (98cm high). You will often see a further four-digit number after the size, such as GGL MK04 3070. That trailing number is the glazing and finish variant (glass specification, pane type and so on), not the size. For fit and flashing, the size code is the part that matters.
VELUX size chart (UK): width letters and height numbers
VELUX windows come in fixed sizes rather than made-to-measure, so every size is a combination of one width letter and one height number from the tables below. Widths run from 55cm up to 134cm; heights run from 70cm up to 180cm.

Width letter
Width

C
55cm

F
66cm

M
78cm

P
94cm

S
114cm

U
134cm

Height number
Height

01
70cm

02
78cm

04
98cm

06
118cm

08
140cm

10
160cm

12
180cm

Put a letter and a number together and you have the size. Some of the most common on Sussex roofs are:

CK02 is 55cm x 78cm, a small window for landings and box rooms.
MK04 is 78cm x 98cm, the single most popular size.
MK06 is 78cm x 118cm, a taller version of the same width.
SK06 is 114cm x 118cm, a wide window for larger loft rooms.
UK04 is 134cm x 98cm, the widest standard size.

Not every letter pairs with every number, so a size you invent on paper will not always exist as a stock product. If you are unsure whether a combination is made, see the full VELUX range or ask us and we will confirm it.
GGL, GGU, GPL and GPU: what the type code means
Before the size, a VELUX roof window carries a type code, and the four you will meet most are GGL, GGU, GPL and GPU. They describe how the window opens and what the frame is made from:

Second letter is the operation. G is centre-pivot (the sash spins on a central hinge). P is top-hung (the sash swings out from the top for a clearer view and more headroom).
Third letter is the finish. L is pine, a timber finish that VELUX supply either clear-lacquered or white-painted. U is white polyurethane, a timber core wrapped in tough white plastic that copes better with steam.

So in practice:

GGL is centre-pivot, pine. The traditional loft-conversion window.
GGU is centre-pivot, white polyurethane. A good choice for bathrooms and kitchens where there is moisture.
GPL is top-hung, pine.
GPU is top-hung, white polyurethane.

The size code (MK04, SK06 and so on) is the same across all four types, so a GGL MK04 and a GGU MK04 need the same opening and the same flashing. That matters when you order, because the flashing kit is priced separately from the window. You can see the wider window options on our roof windows and rooflights page.
How do I find my VELUX size code?
Every VELUX window has a data plate (VELUX call it the type plate) printed on the window itself. To find it, open the window fully by rotating or swinging the sash, then look along the top edge of the sash frame, usually towards the top right. The plate shows the type code and the size code together, for example GGL MK04, along with the manufacture date.
Reading the plate is the reliable way to order a like-for-like replacement, because it removes any guesswork about width and height. If the plate has faded or the window is too high to reach safely, measure the visible glass and the outer frame and bring those figures to the counter, and we can usually work back to the size from there.
How to measure for a VELUX window
VELUX windows are fixed sizes, so you are not measuring the window to order, you are measuring the roof to see which size fits. For a new opening:

Check your rafter spacing. The gap between rafters sets your realistic width. A 78cm (M width) window suits rafters at roughly 600mm centres with a little trimming; wider windows may need a rafter cut and the opening structurally framed.
Measure the structural opening, not just the window. VELUX give a required structural opening for each size in the installation instructions, and it is slightly larger than the window&#8217;s outer frame to allow for fixing and flashing.
Allow room top and bottom. Fitting height affects reach and view, and top-hung (GPL/GPU) windows suit a higher position than centre-pivot ones.

If you are replacing an existing window, ignore all of that and simply read the code off the data plate. Same code in, same code out, and the flashing will match your tile or slate. Not sure which flashing you need for your roof covering? Bring a photo or a tile to our Haywards Heath depot and we will match it.
Getting the right VELUX first time
Read the size code, confirm the type, and order the matching flashing for your roof covering, and a VELUX order is straightforward. Get the flashing wrong or the opening size out and it becomes a return and a delay. If you would rather have a second pair of eyes on it, send us the code and your roof type and get a quote, or call the depot and we will price the window, flashing and any extras together.
Frequently asked questions
What sizes do VELUX windows come in?
VELUX windows come in fixed sizes, not made-to-measure. Standard widths run from 55cm (C) up to 134cm (U), with common letters C, F, M, P, S and U. Heights run from 70cm up to 180cm. Each window is one width letter plus one height number, such as MK04 (78cm x 98cm) or SK06 (114cm x 118cm).
What does GGL mean on a VELUX window?
GGL is a centre-pivot roof window with a pine (timber) finish, supplied either clear-lacquered or white-painted. The sash pivots on a central hinge, and the timber interior suits bedrooms and living spaces. Its sister product, GGU, is the same centre-pivot window but finished in white polyurethane, which handles moisture better in bathrooms and kitchens.
How do I find my VELUX size code?
Open the window fully, then look along the top edge of the sash frame, usually the top right, for the data plate (type plate). It prints the type and size together, for example GGL MK04, plus the date of manufacture. Quote that code for a like-for-like replacement so the opening and flashing match exactly.
What is the difference between a skylight and a VELUX window?
Skylight is a general word for any glazing set into a roof. VELUX is a brand, and a VELUX roof window is an openable unit fitted in the slope of a pitched roof. People often say VELUX to mean any roof window, in the same way they say Hoover for a vacuum, but strictly it is one manufacturer.
How do I measure a VELUX window?
For a replacement, do not measure at all, just read the size code off the data plate and order the same. For a new opening, measure your rafter spacing for the width and the structural opening height from the VELUX installation instructions, which is slightly larger than the window frame. Match the closest standard size to that opening.
How much does a VELUX window cost?
As a guide, a common manual double-glazed centre-pivot window (GGL or GGU) in a size like MK04 is often around £250 to £450 for the window alone, with the flashing kit priced separately. Triple glazing, larger sizes and electric or solar INTEGRA models cost more. Ask us for a current price on your exact size and roof type.

Question 7

Sun Tunnels Explained: Rigid vs Flexible

Accepted Answer

A sun tunnel is a reflective tube that carries daylight from a dome or flat glazing on your roof down through the loft and into a ceiling below, so you get natural light in a room that has no outside wall for a window. It works where a normal roof window or wall window cannot reach, such as a hallway, landing, bathroom or internal WC. VELUX makes them in two versions, rigid and flexible, and two common diameters, roughly 10 inch and 14 inch, with separate kits for tiled and slate roofs.

They are sometimes called a sun pipe, light tube or light pipe. The idea is simple. Light hits the clear dome or glass on the roof, travels down a highly reflective tube that loses very little of it along the way, then spreads into the room through a diffuser set into the ceiling. On a bright day the effect is closer to daylight than to a light fitting, and there is no running cost because nothing is switched on.
How a sun tunnel works
Every sun tunnel has three parts. On the roof sits the top unit, either a clear domed cap for a pitched roof or flat glazing for a flat roof, fitted into a flashing that weathers it into the covering. Inside the loft runs the tube, which is the part that actually moves the light. At the bottom is a diffuser, a translucent disc flush with the ceiling that softens and spreads the light so you do not see a hard beam.
Because the tube reflects light rather than relying on a straight line of sight, a sun tunnel can light a room two floors down from the roof. The shorter and straighter the run, the brighter the result, which is the first thing to think about when you choose between rigid and flexible.
Rigid vs flexible sun tunnel: which one
The choice comes down to what is in the way between your roof and the ceiling you want to light.

Rigid sun tunnel. A solid, mirror-finish metal tube for a straight or near-straight run. It reflects the most light, so for the same diameter and a clear path a rigid tunnel gives you the brightest result. Rigid tube can also cover long drops, with runs from about 0.9 m up to 6 m using extension sections, which suits a light travelling a fair way down through the house.
Flexible sun tunnel. A concertina tube that bends around obstructions such as rafters, purlins, pipework or a water tank. It comes in the 14 inch (350 mm) size. It is quicker to route through an awkward or cramped loft, but every bend costs a little light, so it is best kept short. VELUX recommends keeping a flexible run to around 1.5 m on a pitched roof.

In short, pick rigid when there is a clear line from roof to ceiling and you want maximum brightness, and pick flexible when the loft is tight or something sits in the path. If you are unsure what your roof void will allow, our counter staff have specified these across Sussex and Kent since 1996 and can talk it through with you.
Sun tunnel sizes: 10 inch or 14 inch
VELUX sun tunnels come in two diameters. The smaller is about 10 inch (250 mm, coded 0K10) and the larger is about 14 inch (350 mm, coded 0K14). The bigger the tube, the more light it collects and delivers, so size to the room rather than guessing.

Diameter
Roughly suits
Typical rooms

10 inch (250 mm)
Smaller spaces up to around 14 sq m
Hallways, landings, ensuites, WCs, utility rooms, walk-in wardrobes

14 inch (350 mm)
Larger or darker rooms up to around 19 sq m
Kitchens, family bathrooms, living rooms, home offices

These are guides, not hard limits. A north-facing room, a long tube run or a lot of bends all reduce the light that reaches the diffuser, so if a room sits on the boundary between the two sizes, the 14 inch is usually the safer choice.
Pitched roof and flat roof versions
Sun tunnels are made for the roof you have. Pitched-roof versions are designed for roof slopes of about 15 to 60 degrees and use a domed top to gather light from a low sun across the day. Flat-roof versions, for pitches under about 15 degrees, use flat glazing that sits above an upstand so water runs off. The two are not interchangeable, so check your roof pitch before ordering.
Tile and slate flashing kits
The flashing is the part that seals the top unit into your roof covering, and it has to match what you have on the roof. There are separate kits for profiled and plain tiles and for slate, because the two sit and lap differently. As a rough guide the flashing is made to weather in with slate up to about 8 mm thick, or profiled tiles up to around 120 mm in profile depth. Get this wrong and you invite a leak, so it pays to order the correct kit from the start.
We stock VELUX rigid and flexible sun tunnels for both tile and slate at our depots, alongside the wider range of roof windows and rooflights and the full VELUX line, from roof windows to flashings and blinds. If you are matching a sun tunnel to an existing tile or slate, bring a sample or a photo and we will pair it to the right flashing.
Sun tunnel vs VELUX window: what is the difference
A roof window like a standard VELUX is a glazed unit set into the roof slope. It gives a view, opens for ventilation and floods a room with light, but it needs the room to sit directly under the roof slope. A sun tunnel gives light only, no view and no opening, but it can reach rooms buried in the middle of a house where a roof window would never work. They solve different problems. If the room is under the slope and you want air and a view, fit a roof window. If it is an internal space that just needs daylight, a sun tunnel is the tool for the job, and it is a smaller, tidier job to install.
Buying sun tunnels in Sussex and Kent
Brian Gow Roofing Supplies has stocked VELUX for the trade and for homeowners since 1996, covering Kent, Surrey and Sussex from four depots with delivery across the South East. Call in for a straight answer on which sun tunnel suits your roof and room, or collect the same day. See our Burgess Hill roofing supplies branch for stock and opening hours, or find your nearest branch to get started.
Frequently asked questions
What is a sun tunnel?
A sun tunnel is a reflective tube that brings daylight from your roof into a room below through a diffuser in the ceiling. It lights spaces that have no outside wall for a window, such as hallways, landings and internal bathrooms. It gives light only, with no view or opening, and costs nothing to run.
What is the difference between a rigid and flexible sun tunnel?
A rigid sun tunnel uses a solid mirror-finish tube for a straight run and delivers the most light, and it can cover long drops. A flexible sun tunnel uses a bendable tube that routes around rafters, pipes or a tank in a tight loft. Every bend loses a little light, so flexible runs are best kept short.
What size sun tunnel do I need?
VELUX sun tunnels come in about 10 inch (250 mm) and 14 inch (350 mm) diameters. The 10 inch suits smaller spaces up to roughly 14 square metres, like a hallway or ensuite. The 14 inch suits larger or darker rooms up to around 19 square metres, such as a kitchen or living room. If in doubt, size up.
Can you fit a sun tunnel to any roof?
Most tiled and slate roofs are suitable. There are separate versions for pitched roofs, about 15 to 60 degrees, and for flat roofs under about 15 degrees, plus matching tile or slate flashing kits. You also need a reasonably clear route through the loft. A flexible tunnel helps where beams or pipes get in the way.
Is a sun tunnel better than a VELUX window?
Neither is better, they do different jobs. A roof window gives light, a view and ventilation but needs the room to sit under the roof slope. A sun tunnel gives daylight only, yet reaches internal rooms a window cannot. Choose a roof window for rooms under the slope and a sun tunnel for landings, bathrooms and other enclosed spaces.
How much light does a sun tunnel provide?
On a bright day a sun tunnel gives daylight comparable to a small window, enough to light a room without switching anything on. The amount depends on diameter, tube length and the number of bends. A short, straight, larger-diameter run gives the most, so a 14 inch rigid tunnel delivers noticeably more than a long, winding flexible one.

Question 8

Natural Slate Roofing: Lifespan, Benefits & Costs

Accepted Answer

Natural slate roofing is one of the longest-lasting roof coverings you can specify: a well-laid slate roof usually lasts 100 years or more, and premium Welsh and Spanish slate often reaches 120 to 150 years. In most cases it is the fixings, not the slate itself, that wear out first. That combination of longevity, weather resistance and looks is why architects, conservation officers and experienced roofers keep coming back to it across the South East.

Below we cover how long slate really lasts, how natural slate compares with fibre-cement, the honest disadvantages, and what to check when you are sourcing it for a job in Sussex or Kent.
How long do slate roofs last?
Natural slate is a metamorphic stone, so its performance is built into the material rather than added as a coating. High-quality slate that has been correctly specified and installed comfortably passes 100 years. Welsh slate such as Penrhyn and Ffestiniog can last well beyond that, while good Spanish slate typically gives 100 to 150 years. Lower-grade imports are a different story and may only manage 50 to 75 years, which is exactly why grading and source matter.
The catch is that the whole roof is only as durable as its weakest part. Nails and other fixings often give out at around 60 to 80 years, so many full strip-and-re-lay jobs happen at 70 to 100 years even when the slate itself is still sound. Specifying the right fixings from the start, and re-using slate where it is genuinely reusable, is part of getting that lifespan on paper into a real roof.
Built for the British climate
Natural slate suits the UK&#8217;s mix of frost, wind-driven rain and long damp spells. It resists water absorption, does not warp or fade in UV, and holds its structural integrity through decades of freeze-thaw cycles. Unlike some manufactured coverings, it does not rely on a surface finish that degrades over time. Once it is on, a slate roof needs very little attention, which keeps call-backs down and gives homeowners a genuine fit-and-forget covering.
Natural vs fibre-cement slate
We stock both natural slate and fibre-cement slate, and the right choice depends on the job and the budget. Fibre-cement slates are lighter, cheaper per square metre and quick to lay, which makes them a sensible option on new builds, extensions and rental properties where the budget is tight. Natural slate costs more up front but lasts far longer and keeps its appearance because the colour and texture are in the stone, not a coating.

Feature
Natural slate
Fibre-cement slate

Typical lifespan
100 years or more
Around 30 to 60 years

Material
Natural metamorphic stone
Cement, fibres and fillers, coated

Appearance over time
Colour and grain stay in the stone
Surface coating gradually weathers

Weight
Heavier; structure must suit
Lighter and more uniform

Up-front cost
Higher
Lower

Best for
Heritage, conservation, premium homes
Budget-led new builds and extensions

Fibre-cement is a manufactured product, so slates are very consistent in size and thickness, which speeds up laying. Natural slate needs sorting and grading on site, but rewards it with a depth and character no manufactured slate quite matches. Brands like Cembrit and Marley cover the fibre-cement side, and we can talk both through against the property and the budget.
The honest disadvantages of a slate roof
Slate is an excellent covering, but it is not the answer to every job, and it pays to be straight with clients about the trade-offs.

Cost. Natural slate carries a higher material and labour cost than concrete tiles or fibre-cement. The lifecycle cost stacks up well over 100 years, but the up-front figure is real and needs to be quoted honestly.
Weight. Slate is heavy. The roof structure has to be able to carry it, and on a re-cover you may need to check the timbers rather than assume the old roof&#8217;s loading transfers across.
Skilled fixing. Slating is a craft. Even courses, correct headlap, sound nailing and clean detailing at ridges, hips and valleys all take an experienced roofer. A poorly laid slate roof will let you down long before the slate does.
Grading and waste. Natural slate varies, so some sorting and cutting on site is normal. Buying from a supplier who grades properly keeps that waste down.

Consistency and complete systems on site
From an installation point of view, consistency is everything. Properly graded and sized slate lets roofers keep even courses, achieve clean lines and work efficiently across the roof. Variations in thickness or sizing slow the job and show in the finished result, so sourcing from a specialist who grades accurately reduces wastage and protects the finish.
A slate roof is also more than the slates. It relies on the right battens, underlay, fixings and matching accessories such as ridges and hips, all working together. We supply slate as part of a complete pitched roofing system so the components are compatible, which is the practical side of following BS 5534, the code of practice for slating and tiling. Natural slate is usually laid at pitches of roughly 20 degrees or steeper, with the exact minimum depending on slate size, headlap and how exposed the roof is.
Sourcing natural slate in Sussex and Kent
Brian Gow Roofing Supplies has been a family-run roofing merchant since 1996, and slate is one of the lines we know best. We cover Kent, Surrey and Sussex, holding natural and fibre-cement slate along with the fixings, underlay and dry-fix accessories that go with it, and we deliver across the South East or you can collect from a depot.
Because we deal with trade and homeowners every day, the advice is practical rather than salesy: the right slate for the property, matched components, and a realistic view of cost and lifespan before anyone commits. If you are pricing a job near the coast or picking up locally, our Hailsham roofing supplies depot carries slate and the rest of the pitched-roofing range.
For a price on natural or fibre-cement slate, tell us the property and rough quantities and get a quote, or call the branch and we will sort the specification with you.
Frequently asked questions
What are the disadvantages of a slate roof?
The main drawbacks are cost, weight and the skill needed to fit it. Natural slate costs more up front than concrete tiles or fibre-cement, it is heavy so the structure must be able to carry it, and it needs an experienced roofer to lay even courses and detail it correctly. Get those right and it repays the investment for a century or more.
How long do slate roofs last?
A well-laid natural slate roof usually lasts 100 years or more, with premium Welsh and Spanish slate reaching 120 to 150 years. The fixings often wear out before the slate, so many roofs are stripped and re-laid at around 70 to 100 years even when much of the slate can be re-used.
How often should a slate roof be replaced?
A good natural slate roof rarely needs full replacement inside 80 to 100 years. Long before that, the usual work is repointing ridges, replacing slipped or cracked slates and renewing failing fixings or flashings. A full strip-and-re-lay tends to happen when the nails or battens give out rather than the slate.
What is the difference between natural and fibre-cement slate?
Natural slate is quarried stone that keeps its colour and lasts 100 years or more. Fibre-cement slate is a manufactured board of cement and fibres with a coloured coating, lighter and cheaper but with a shorter life of roughly 30 to 60 years. Natural slate suits heritage and premium work; fibre-cement suits tighter budgets.
How much does it cost to replace a slate roof in the UK?
Cost depends on roof size, pitch, access and whether you use natural or fibre-cement slate, so figures vary widely. Natural slate sits at the higher end because of material and labour. For a sense of scale before you price a job, this guide to typical UK new roof costs breaks the options down, and we can quote the materials once you know the plan.

Question 9

Handmade Clay Roof Tiles for Heritage Properties

Accepted Answer

Handmade clay roof tiles are individually formed and kiln-fired using methods that have changed little in generations, which is why they remain the standard choice for listed buildings, conservation areas and period homes where a new roof has to match old work. They carry the subtle variation in colour and shape that historic roofs have, they can last well over 100 years when laid correctly, and they satisfy most conservation officers who insist on a like-for-like material.

Why handmade clay tiles suit heritage and period work
On heritage and conservation projects, appearance matters as much as performance. Every handmade tile is formed and fired on its own, so no two are quite identical. Those small differences in colour, camber and texture are not faults. They are exactly what lets a new roof sit comfortably next to a 200-year-old one instead of looking flat and machine-stamped.
Planning authorities and conservation officers often require roofing that closely matches the original fabric of a building, and handmade clay is usually the material they have in mind. That makes it a sensible first choice for:

Listed buildings
Properties inside conservation areas
Period homes, oast houses and farmhouses
Extensions and additions to traditional buildings

Get the profile and finish right and you keep the planners happy and the client happier.
Handmade vs machine-made clay tiles: what is the difference
Both are made from clay and both are fired, so the raw material is the same. The difference is in how they are shaped. Machine-made clay tiles are extruded or pressed to tight, repeatable dimensions, which gives a uniform, regular roof and lets them be laid at slightly lower pitches. Handmade tiles are shaped by hand, so they vary from tile to tile and give the roof depth and movement that machine tiles cannot copy.
That variation is the whole point on heritage work, but it does change how the tiles behave on the roof. Here is the short version:

Factor
Handmade clay
Machine-made clay

Appearance
Irregular, characterful, matches historic roofs
Uniform and consistent, cleaner modern look

Dimensional tolerance
Looser, tiles vary slightly
Tight and repeatable

Typical minimum pitch (plain tiles)
Around 40 degrees
Down to 35 degrees

Cost per thousand
Higher
Lower

Best suited to
Listed and conservation work, period homes
New builds and general residential roofs

Neither is better in the abstract. For a farmhouse re-roof in a conservation area you want handmade. For a straightforward new build you may not need to pay for it. We stock both clay and concrete tiles, so bring us the job and we will help you weigh up cost and lifespan against the look you are after.
How long do clay roof tiles last
Lifespan is one of the strongest arguments for clay. Laid and maintained properly, handmade clay tiles can last well over 100 years, comfortably outliving the fixings and often the battens beneath them. It is common to strip a Victorian roof and find a good proportion of the original tiles still sound enough to reclaim.
Clay is naturally resistant to frost, UV and general weathering, and it holds its colour rather than fading the way some pigmented materials do. It does not corrode and it will not lose a surface coating, because the colour runs right through the fired clay. For any project where authenticity and long service life matter, that durability is hard to argue with.
What is the minimum pitch for clay roof tiles
For handmade clay plain tiles the practical minimum is usually around 40 degrees. BS 5534, the code of practice for slating and tiling, sets that higher figure because the natural variation in handmade tiles puts them outside the geometric tolerances that would otherwise allow a 35-degree pitch. Machine-made plain tiles that do meet those tolerances can be laid down to 35 degrees.
Interlocking clay tiles are a different case. Their overlapping edge lets them shed water at lower angles, so they can typically be laid down to about 30 degrees, and some low-pitch interlocking designs go lower still. If your roof sits near or below these figures, the pitch drives the tile choice, so it is worth checking before you specify. Our team can talk through the options for your pitched roofing project and confirm what will pass.
Breathability and moisture management
Older buildings were built to let moisture move through the structure rather than trap it. Clay tiles work with that principle. Paired with a suitable breathable membrane, a clay roof lets water vapour escape instead of holding it against the timbers.
Handled correctly, that breathable build-up helps:

Reduce condensation forming in the roof space
Keep rafters and battens dry
Lower the risk of rot and decay over time

Ventilation and membrane choice have to suit the specific roof, so on solid-wall period properties in particular it pays to get the detail right rather than assume a standard modern build-up will do.
Clay tiles for listed buildings across Sussex and Kent
The South East has a lot of the building stock that handmade clay was made for. Sussex and Kent are full of tile-hung cottages, oast houses, weatherboarded farmhouses and Victorian terraces, much of it inside conservation areas or individually listed. Re-roofing that stock without an approved like-for-like tile is a quick way to a refused application.
Brian Gow Roofing Supplies has been supplying roofers and homeowners across Kent, Surrey and Sussex since 1996, and matching tiles for heritage work is bread and butter for us. We can help identify what is already on a roof, source a handmade tile that reads correctly against it, and supply the matching ridges, hips and fittings so the finished job looks of a piece. You can collect from our Hailsham depot, browse our Sussex roofing supplies, or arrange delivery across the South East.
Getting the right tiles, gauge and fittings
Handmade clay rewards experience. Matching an existing roof, setting the correct gauge so the coursing lines up, and choosing compatible ridge and hip tiles all make the difference between a roof that looks right and one that looks patched. Getting the fittings wrong is expensive to put back.
That is where a specialist merchant earns its keep rather than a general builders&#8217; yard. Bring us the details of the job, or a sample tile if you have one, and we will advise on tile, gauge, layout and fittings before you commit. When you are ready to price it up, get a quote or call your nearest branch and we will sort the rest.
Frequently asked questions
What are the benefits of handmade clay roof tiles?
Handmade clay tiles give a roof authentic character, with the subtle variation in colour and shape that historic buildings have. They last well over 100 years, resist frost and UV, hold their colour because it is fired through the clay, and are usually the material conservation officers accept for listed and period properties.
How long do clay roof tiles last?
Correctly laid and maintained, clay roof tiles can last well over 100 years. Clay resists frost, UV and weathering and does not lose surface colour, so the tiles frequently outlast their fixings and battens. When an old roof is stripped, many original clay tiles are often sound enough to reclaim and reuse.
Are handmade clay tiles suitable for listed buildings?
Yes, they are usually the preferred choice. Conservation officers and planners generally require a like-for-like material on listed buildings and in conservation areas, and handmade clay closely matches the look of historic roofs. Using the correct profile and finish, and matching the existing tile, helps a re-roofing application gain approval.
What is the difference between handmade and machine-made clay tiles?
Both are fired clay. Machine-made tiles are pressed to tight, uniform dimensions for a regular roof and can be laid at slightly lower pitches. Handmade tiles are shaped individually, so they vary from tile to tile and give a roof depth and character. Handmade suits heritage work; machine-made suits general residential and new-build roofs.
What is the minimum pitch for clay roof tiles?
Handmade clay plain tiles are usually laid at a minimum of around 40 degrees, because their natural variation falls outside the tolerances that let standard machine-made plain tiles go to 35 degrees. Interlocking clay tiles can typically be laid down to about 30 degrees, with some low-pitch designs going lower. Always check pitch before specifying.

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