Even people involved in the building industry may not be aware that there are different types of Lead Sheet available. The two commonest are Rolled Lead that conforms to the British Standard: BS EN 12588 plus most standard building specifications and a “Cast” sheet that doesn’t.
Rolled Lead Sheet is manufactured to precise and consistent thickness tolerances using high specification rolling mills that ensure the maximum performance standards and lifespan for the finished product.
The modern “Cast” Lead Sheet (opposed to traditional Sand Cast Lead Sheet) is made using a continuous casting machine that cannot deliver thickness consistency in the finished product due to the crude method of manufacture. This is why it doesn’t achieve the quality required to conform to the British Standard: BS EN 12588.
BS EN 12588 standard was drawn up to ensure the maximum lifespan for Lead Sheet and flashings used in construction and based on decades of experience. This statement is fully supported by a 20 year study carried out at Cambridge University that discovered premature failure caused by the thickness variations in samples of modern Machine Cast Lead Sheet.
If you want to be sure the Lead you are fitting will last as long as it should (and that could be 100 years or more) you should only fit British Standard Rolled. That’s why most standard build specifications will state:
“Lead Sheet to BS EN 12588, to be fitted in accordance with BS 6915 and the recommendations of the Lead Sheet Association (as defined and illustrated in ‘Rolled Lead Sheet’ – The Complete Manual).”
That means Rolled Lead Sheet must be used. Fitting Machine Cast Lead will be out of specification and could leave you liable.
Always choose British Standard Rolled Lead and cast aside any worries of call backs or flashing failure.