No matter what sort of roof you have – whether it’s a traditional pitched roof covered with slates or tiles, or a more modern flat roof – at some point it’s going to meet a wall, a chimney or another roof, inevitably leaving some sort of a gap. Obviously, if the roof doesn’t actually overhang the gap, you need something to seal the gap to make it watertight. That’s where flashings come in.
What are flashings?
In their simplest terms, flashings are sheets of material that are put in place to cover the abutment between the roof and an adjacent surface. They come in a variety of types to cope with the range of different possible angles that occur on a roof, and can be made out of several different materials. Let’s look at the materials first.
Traditionally, the best flashings were made of lead – as a soft and malleable metal it’s easily worked into the desired shape (though working out the desired shape is a skill in itself!) and is long-lasting in all weather conditions. But it’s relatively expensive.
Zinc is a good deal cheaper than lead. But it’s less flexible and less hard-wearing, and arguably looks cheaper than lead too. If your zinc flashings are worn out, you may find that it’ll be cheaper in the long run to replace them with lead and save the cost of future repairs.
Cheap and easily applied, these are common on older pitched roofs, and may have cut tiles set into them for further water deflection. But they can be problematic because of shrinkage as they age.
These are unwieldy and don’t have much application beyond the simple cover flashings over the skirtings of flat felt roofs.
We’ll have a look at the various types of flashing and the joins they cover next time.