What Code of Lead Is Used for Flashing?

Lead sheet is graded by code, a single digit that stands for its thickness and weight. A flashing closes the gap between a tiled slope and the wall, stack or upstand beside it. For that work the Royston brochure on cast lead names Codes 4, 5 and 6. The brochure gives each code its own identifying colour: blue for Code 4, red for Code 5 and black for Code 6.

Code 5 is the one to remember, because Checkatrade's June 2026 cost table prices stepped lead flashing in Code 5 at £80 to £120 per metre, as a typical UK range. Code 4 is the lighter option for simple or sheltered details, where the piece is short and the lead does not have to span far. Code 6 is thicker again and belongs on larger, more exposed pieces, where extra stiffness and body count for more than ease of shaping.

No single code is right for every roof. The correct one follows from the size of the piece, how exposed the spot is and how the lead will be held. Whichever your roofer picks, the code belongs in the written quote, so you can see what will be fixed to your house and raise it if the lead delivered differs.

These are the thicknesses and weights from the Royston brochure, with the uses it lists for each. Treat them as a guide, and check the manufacturer's current data for your project before anyone orders sheet.

Royston recommends Code 3 for soakers only. Code 4 is the only code it lists for soakers, flashings, sloping valleys and dormers all at once. Codes 5 and 6 are named for flashings, and for gutters and dormers too. Codes 7 and 8 are thicker again and are listed for gutters and dormers, not for flashings.

Heavier lead is stiffer and costs more, but it is not automatically better. Over-thick sheet is harder to dress into tight corners, and a piece that is too long will crack in any code, as our answer on why lead flashing cracks explains.

Soakers are the little bent lead pieces that hide under the tiles beside a wall. The brochure recommends Code 3 for them, with Code 4 also listed. They are thin on purpose, because each one has to fold neatly beneath a tile or slate and lie flat there without lifting it. Our answer on what lead soakers are explains how they work with the flashing above them.

Dormer cheeks and other pieces that wrap round a shape fall under the heavier codes in the brochure. A roofer will often settle on Code 4 or Code 5 depending on the size of the cheek and on whether the lead has to be bossed into tight corners. Thicker sheet resists bossing, so the choice is a balance between strength and workability.

If a quote does not name a code at all, ask for one. A phrase like "new lead flashing" could mean thin sheet that will not last, and with no code written down you have no fair way to set one price against another. A named code also gives you something to point to if the lead fails early.

This page is the quick answer. The full explanation, with how a code is chosen, how the thickness can be confirmed and why the numbers run the way they do, is in our lead sheet codes explained guide. If you are weighing lead against another material for a flashing, the lead-free flashing question has its own answer on this site.

Lead is a long-lived metal. A published cost guide gives over 80 years for lead flashing, which is a best case in good conditions and not a promise. Your choice of code helps decide how near to that a given detail gets, alongside the fixing method and the length of each piece.

When we survey, we look over the existing lead, note the code where we can tell it, and photograph each detail before we price the job. What you receive afterwards is a single written price, and the code for each part of the job is stated in it. You will find the wider trade explained on our lead work page, including valleys, abutments and the rest of the details.