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’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. If you would rather have the leadwork done than fit it yourself, we also carry out lead work as a service. 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.