Why Important
Lead is a malleable sheet metal which can be folded, welded and beaten to form any shape required to accommodate a roof.
What to look for
These are made of long sheets of lead dressed over timber rolls and held in place by lead clips, which are screw-fixed to the timber under the lead sheets and bent up over them.
Ridge and hip flashings can fail if these fixings are not maintained; clips should be checked and pushed back down if affected by wind lift.
Lead sheet can crack, tear or buckle. If the surface is not visually flat, then check the sheet for problems. Growing of mould or any vegitation on the roof indicates cracks in those locations.
When to look
At least annually, and after large weather temperature changes.
How to fix
Lead expands and contracts readily in response to changing temperatures and must be laid carefully to accommodate this or it will tear or buckle. Sometimes failed lead sheet is replaced with zinc, which is cheaper, however lead is preferable and will give a longer life if properly detailed.
Avoiding creating problems
Lead should always be laid by a skilled lead plumber, preferably to drawings by an architect experienced in conservation work. The Lead Sheet Association has developed a series of details for leadwork which should be followed to avoid problems.
Historical background
When Lead sheet became cheaper in the 19th Century lead sheet was the material predominantly used for ridge and hip flashings, and as well as complete roofs (such as Church Roofs).