Code 7 Lead is 3.15mm thick(a 19% increase over code 6 lead) and weighs 35.72kg/m2 (Thickness to BS EN12588 tolerances of +/- 5%)
If the roof you are working on is exposed to more severe weather, or you are working on a historical or listed building, code 7 lead can be used on for almost every aspect of pitched roofing or flat roofing. However, for many applications on severe weather exposed roofs and even for items like soakers or damp proof courses on a historical or listed building, a thinner gauge is more appropriate.
Although code 6 lead is usually sufficient for almost all applications, any area where there is a risk that moss and/or lichen may be present on the slates or tiles might benefit from the increased strength and protection of code 7 lead.
As with some of the slightly thinner gauges of lead, the increased thickness means that code 7 lead has increased resistance to thermal movement you can safely keep the maximum length of flashing at 1.5metres. JJ Roofing Supplies standard roll lengths of 3 and 6 metres will therefore give you either 2 or 4 lead flashing strips to work with.
As with all lead work, it is important to use a lead sealant that allows for thermal expansion and contraction, avoiding the problems of resistance to water ingress and the mould, rot and other water damage that can result.
Due to the increased gauge of code 7 lead, it is particularly important to carefully apply patination oil to the newly laid lead, not only on the surfaces, but even on the underside of flashing, ensuring that you get a great looking finish both before and after the final patina develops.
New lead can develop a corrosion product, lead carbonate, in damp or rainy conditions which leaves a non-adherent coating on the surface of the lead which is not aesthetically pleasing. The simple solution for this is the application of a thin coat of patination oil on all newly installed items.