Thousands of years after the Romans pioneered lead for all sorts of applications, we still use it as an important architectural metal. In particular, lead is very commonly used in roofs, as waterproofing for joins, gaps, and abutments. This use of lead is called lead flashing. But different types of lead flashing have different requirements in terms of lead, hence the development of different lead codes. The lower numbers are lighter, while the higher ones are progressively heavier.
It isn’t just the weight that is important though. The thickness of the lead also affects the lead’s thermal movement and how strong the lead will be. Furthermore, lighter lead is much easier to work with and more malleable.
Code 3: Soakers
This is very lightweight by lead standards. Code 3 lead is easy to work with but its light weight primarily makes it suitable for making soakers and little else. Soakers are L-shaped constructs set where a pitched roof hits a chimney or abutment. They catch the water that would normally settle in the gaps and redirect it so it goes towards the gutter.
Code 4: All-Rounder Lead Flashing
This is probably the most versatile and commonly used of the lead codes. Code 4 is suitable for standard flashing work and can even be used for soakers on buildings that require more robust abutment protection. If you live in a new build with a pitched roof this is probably the lion’s share of the lead flashing that’s on your roof right now. The exception is tapered valley gutters. Tapered valley gutters require a somewhat stronger lead.
Code 5: Church Flashing
While Code 4 is more easily workable, Code 5 has it beat in robustness while not being so heavy as to be impractical in many of the same roles – though not soakers. For this reason Code 5 is most often used in churches and listed buildings that often require superior reinforcement to Code 4 lead. Code 5 can bear heavy weather much better. It sees a lot of use on older roofs that need more reinforcement.
Code 5 is also where lead becomes to be thick enough to be plausibly used on flat roofs for waterproofing. It is also a feasible option for valley gutters, both tapered and pitched, as well as dormers.
Code 6: The Enforcer
After Code 5 the lead codes start to become more specialised again. Code 6 is so heavy it is no longer able to be used as vertical cladding without being prohibitively expensive to fit properly. However, it can still be used for valley gutters, dormers, balconies, and flat roofs.