Roof Flashing: What is it and Why Do We Need it?

If you look at many houses, you can spot flashings on external areas of a property. This might include, walls, porches, windows and doors - you can find them as part of foundations, too. The most common place for flashing to be is the roof.

A slate roof with some of the lead flashings also visible.

Essentially, anything rising through to, or joining the roof, will have a flashing. For example, chimneys, skylights, and vents all have a flashing at the point of which they join, or go through, the roof.

Why do we need roof flashing?

Roof flashings are fitted primarily to maintain a watertight roof. Without a flashing fitted, rain water would run down the chimney, or the higher area of roof tiles, and just disappear into the house interior where the chimney rises through the roof.

If, on a house that has a pitched roof with two roofs joining on both sides - called the valleys – there was no flashing built into these valleys, rain water running down the roofs would simply pour straight down into the house. By fitting flashing, it safeguards the joints against not being watertight.

It is not possible to take shortcuts or use other methods to try and replace the role that flashing offers. Bonding agents and cement fillets will see water still finding its way in, and with the cement, it will break away over time, leading to major gaps appearing.

What materials are used for roof flashings?

In the past, pretty much every example of flashings were used from lead sheet. Lead was predominantly used due it being a soft and easily workable metal. The flashings that were created from lead could be easily moulded to a whole host of shapes without the worry of splits of cracks appearing.

Thanks largely to rising costs, along with concerns over lead contamination, materials such as rubber, zinc sheet, and plastic, were introduced. Where lead is still used, it is usually painted with a waterproof paint.

The importance of well-fitted roof flashing

Here at D & C Roofing, we simply cannot express how essential it is to have properly fitted roof flashing. If flashings aren’t fitted correctly or are substandard, those nice new tiles that have been fitted will matter not! You could spend as much as you like on top of the range tiles, but if you have poorly-fitted flashings, rainwater will breach the roof, which will lead to massive internal problems, such as damp, eventually causing ceilings to come down if the fault isn’t swiftly rectified.

If you are looking to have you work done on existing flashings on a property, or if you have a new project that requires roof flashing, then give us a call here at D & C Roofing. Our highly-recommended roofers in Devon and Somerset are on hand to make sure you get the best job possible!

Image: Bryn Pinzgauer under Creative Commons.

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