Why Important
Lead is a malleable sheet metal which can be folded, welded and beaten to form any shape required to accommodate a roof.
Lead can also be used in place of mortar at abutments. This may have a minor impact on the appearance of the roof, but if laid properly and secured, lead should have a long life with little maintenance.
What to look for
Lead sheet became available for Ridges and Hips during 19th Century, so you are likely to find this material on Victorian and Edwardian buildings.
Mortar skews protect the junction between the roof and the wall.
Prior to the introduction of lead, these junctions were covered with shaped stone ridge pieces, or clay ridge tiles fixed down with mortar and held in place from wind uplift by their own weight.
When to look
How to fix
If a lead watergate is unacceptable for aesthetic reasons, it may be possible to insert lead soakers under the slates, cover these with a strip of expanded stainless steel lath as a key and apply a mortar fillet over, thus giving the appearance of a mortar skew with the water-tightness of lead.
Avoiding creating problems
Lead expands and contracts readily in response to changing temperatures and must be laid carefully to accommodate this or it will tear or buckle.
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.