Draining water from shared valleys can add complications that some designers overlook. We came across a case in point, which we illustrate in the photo that accompanies this post. The builder had repeated the same drainage angle they used at each end of the composite building. But they seem to have overlooked the fact that the valley carried twice as much rainwater.
Pooling Water From Shared Valley Drains
The roofs in question were tiled with overlapping shingles. This meant their upper edges were covered over by shingles above them. Although by definition their lower edges were exposed, on the assumption water would flow over them. However, this assumed the moisture did not pool.
When the composite building experienced heavy rain, the water backed up over the standard drain-spouts that were incapable of coping with the abnormal flow. The water level rose above the lower edge of the bottom row of shingles. Natural capillary action then drew the moisture into the roof space causing damp.
Our clients were anticipating a large repair bill, when they called us for advice about draining water from shared valleys. But we had a trick up our sleeves that saved them time and money. We solved their problem by installing larger down spouts that we use on commercial and industrial buildings.
Designing Trouble-Free Effective Roof Valleys
Roof valleys receive water from two adjoining roof surfaces, meaning they may have to work twice as hard as eavestrough systems on the outer edges of buildings do. There are three common ways to seal valleys on shingled roofs, so they don’t leak and cause damp in the roof space:
Cut Valleys With Waterproof Membranes
The cut valley solution is a popular way for draining water from shared valleys. The roofer installs a flexible waterproof lining along the valley, before overlapping it with the lowest row of shingles. This is a reliable, durable option.
Masking Valleys With Weaved Shingles
Cut valleys create a contrast line that may disturb the smooth visual impression of a shingle roof. Some homeowners ask us to flow the shingles across the valley by weaving them together. This may work for a while until the shingles begin to age, and so is not a permanent solution.
Exposed Metal Valleys Make a Statement
If you can’t solve a problem, then make a feature of it, as the old proverb goes. Metal valleys work the same way as cut valleys do, except they use a designer material to create a striking appearance that makes an architectural statement.
Get More Sound Advice From Valiant Exteriors in Calgary
Valiant Exteriors offers Calgary residents a one-stop solution for keeping their homes waterproof, and protected from the elements. But our services do not stop at draining water from shared valleys as we share in this post.
We offer a full range of quality sidings, superior eavestroughing, and expert asphalt roofing repairs. We are easy people to work with and our prices are fair.
You can contact us by calling (403)829-1661, writing to [email protected], or completing a short inquiry form. We’ll be delighted to hear from you and help you solve your problem!
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Image: A Series of Roof Valleys ©Valiant Exteriors