Flashings are mainly used to seal joints where a roof meet a vertical surface such as a wall, around chimneys and at roof lights. Traditionally lead has been used because it is malleable and can be ‘dressed’ to follow the irregular profiles of masonry and roof coverings. It is also very long lasting. especially in its heavier grades. It is quite normal to find code 4 lead still in good condition after 80 or 100 years. If it is damaged it is usually more to do with careless repairs to surrounding roofing than to intrinsic failure or problems with weathering. Lead is also susceptible to theft.
However the manufacturing of lead is associated with serious pollution problems, particularly in parts of the world where environmental standards are low or not enforced.
Alternatives to lead flashing include the following:
- zinc – This is commonly used on the continent but is relatively difficult to find in the UK. There are a few companies selling it in its ‘soft’ form which designed for flashing and soakers
- aluminium – This is available in a ‘soft’ form from a few suppliers and, apart from its highembodied energy, is a good alternative. It comes with various surface finishes which give it a matt finish. e.g. Klober Easy-Form. Although aluminium is high in embodied energythe total amount of energy it takes to make a material (or a building). See more on embodied energy, the amount used in flashing is relatively small.
- GRPglass reinforced plastic, also commonly known as fibre glass – This is a good alternative provided that it is going onto flat surfaces as it is rigid and cannot be dressed. (whereas valley gutters in GRP come preformed at various angles.)
- EPDMethylene-propylene-diene monomer. often used as a roofing membrane – this is available from some of the plastic sheet roof suppliers. It has a thin aluminium backing so that it can be dressed to fit the wall surface and slates
- copper – this is a specialist item sometimes used in conjunction with copper roofs.
The Single Ply Roofing Association produces a design guide for single ply roofing with lots of useful information.