A lead valley is a traditional lead flashing that is used when two roofs come together to make an internal corner on a roof. A sheet of lead is prefabricated to size and fixed onto the lay boards of the valley and then the roofing tiles overlaps the lead to make it watertight. Lead valleys can used with the majority of roofing materials and are the preferred choice of many roofers due to the longevity and reliability that lead offers.
Lead valleys can easily be either dressed or welded to overcome any situation. If a valley is required to return and turn around a corner, lead can easily be dressed around the corner leaving it tight to the roof and completely waterproof. When using hard metals, the metal valleys are left long leaving a gap underneath the valley on the corner. This is not aesthetically pleasing and can cause future issues down the line with driving rain.
Due to the lead valleys malleability, they can be fitted to curved roofs without any special machinery. The lead can be bossed to suit any curve whether a small or large radius using traditional lead worker hand tools.
When replacing an old roof, experience shows that they are rarely straight. Another benefit of a lead valleys malleability is the ability to overcome slight movements in what would have normally been a straight valley.
Lead valleys and flashings are known to last well over 50 years therefore, once installed you have piece of mind knowing you will never have to replace them again.
Lead is resistant to atmospheric corrosion and have been proven to withstand extreme weather conditions.
Whilst the initial outlay of lead valleys is slightly higher compared to other products, the life span of lead compared to other products is far superior therefore, lead valleys are more cost effective in the long run.
Lead valleys should only have 2 rows of copper fixings and the top of the sheet of lead. A common mistake made by unexperienced installers is to put copper fixings down bothedges of the valley. By doing this the lead is unable to expand and contract freely therefore, over time the lead will split causing the roof to leak. Only on extreme roof pitches such as 60deg + should copper fixings be used down the sides of the valley, and they should be limited to the top third of the valley so movement can still occur.
Another common mistake is to install the lead in too long of lengths, this will also cause the lead to split due to the inability to move freely. Lead valleys should not be installed in longer lengths than 1.5m, the only exception would be if thicker (30kg or above) lead was specified in which lengths could be increased to 2m. In reality, it is more economical to use 1.5m lengths as the lead rolls come in lengths of 3m.
When inexperienced installers fit lead valleys especially when trying to manipulate the lead around corners, they excessively hit the lead in the same spot causing the lead to thin out. By thinning the lead, they not only are more likely to split the lead themselves but they also reduce the lifespan of the lead. Lead should be dressed and bossed by skilled lead workers who understand how to move the lead without causing excessive thinning of the lead.