Rolled (Milled) Lead Sheet to BSEN 12588:2006
Lead sheet has been produced by rolling since the mid 1700’s and by the turn of this Century, rolled (milled) Lead sheet was being used in the UK as an alternative to sand cast sheet for roofing and weathering.
Rolled Lead sheet is formed by passing a slab of refined lead back and forth on a rolling mill between closing rollers, computer controlled to obtain an exact predetermined thickness.
The sheet is then slit to width and cut to length for final packing and distribution.
Such is the consistency of the process that rolled sheet will not vary in thickness by more than +/- 5% at any given point.
Which is why Rolled Lead sheet is the only type that is manufactured to a British and European Standard.
BSEN 12588:2006 specifies thickness tolerances and chemical composition in order to produce a consistent microstructure.
The minimal variance in thickness means that when Lead sheet is fitted to a roof, the extent of thermal movement can be accurately predicted and the correct fixing method adopted.
The technical advice and literature of the Lead Sheet Association is based solely upon the use of rolled lead sheet to BSEN 12588:2006 and the design and construction of fully supported lead sheet roof and wall coverings (BS6915:).
It cannot be assumed to apply to either the sand-cast or machine-cast Lead sheet described below, as the thickness tolerances are wider and more inconsistent than British and European Standard rolled Lead sheet.
This is particularly relevant when considering thermal movement and appropriate design and fixing methods.
Technical enquiries regarding sand-cast or machine-cast Lead sheet should be referred to the manufacturers or suppliers of these products.