Lead vs lead substitutes on a dormer
Short answer
Real lead (code 4 or 5) is the proven default — dressable, very long-lived, easy to repair. Modern rubber-bitumen and butyl substitutes (Wakaflex, Easyform, Ubiflex) are faster to install and cheaper, with comparable lifespan when properly detailed. Pick one system and stay with it for the whole dormer.
Lead vs substitutes
| Aspect | Lead (code 4/5) | Substitutes |
|---|---|---|
| Lifespan | 30–60 years | 20–40 years |
| Cost (material) | Higher | 20–35% lower |
| Install time | Slower — needs dressing | Faster — flexible roll |
| Dressability | Excellent | Good |
| Repair | Easy, anyone can do it | Brand-specific |
| Run-off | Lead in rainwater (small) | Cleaner |
| Look | Traditional | Closer to plain dark band |
Lead in detail
Lead is sold by code: code 3 is too thin for a dormer, code 4 is fine for soakers and side flashings, code 5 is the safe choice for the main apron. Lead must be dressed (bossed) into the tile profile, not just laid flat — that is the single skill that decides whether it lasts 10 years or 50.
Substitutes in detail
Modern substitutes are a rubber-bitumen sheet with a butyl underside and a flexible top layer that can be dressed by hand. The good brands are warranted for 20+ years. The cheap brands degrade in UV after 8–10 years. Ask which brand and which thickness — these matter more than the category.