Ways to Shingle a Roof Valley

A valley, in the natural sense is elongated lowland between ranges of mountains, hills, or other uplands, often having a river or stream running along the bottom. An open valley like this is part of nature’s drainage system.

Roof valleys are also spots where something changes direction, in this case the elevations of the roof. These are focal points for water to drain away. We discuss two ways to shingle a roof valley in this post, to optimize our waterproofing.

More About the Valleys on Our Roofs

It’s essential we give careful attention to roof valleys, because these are areas where water could potentially enter into the roof space. We want to make sure it flows away safely instead. There are two methods worth considering.

What follows is of course a generalization. That’s why we prefer to view a client’s home, before we decide the best way to shingle a roof valley securely on that particular property.

The Two Main Roof Valley Types

Open Roof Valleys: Open valleys have shaped metal strips along the centre of the plane, where the two roof surfaces meet. These strips could be galvanized, copper, aluminium, zinc alloy, or steel coated  sheet, subject to local building codes. The profile may be V or W -shaped subject to the application.

The two roof planes overlap this sheet, but stop a distance from the center line to admit water flows. Careful attention is needed to the design of this roof joint, to make sure the water flows down the sheet to the eavestrough, and not into the roof space

Closed Roof Valleys: Closed valleys have continuous shingle flowing over them, so the roof surface becomes the drain. It can be wise to fit a metal ‘in case’ sheet beneath this as ‘belts and braces’ insurance.

Understanding the differences between these valley treatments, and which one to use, is therefore an important step in our quest for a shingle roof that remains waterproof regardless of the weather.

The Best Way to Shingle a Roof Valley

There are pros and cons to which method is best. An open roof valley provides the most efficient drain. But many Calgary home owners prefer the smooth flow over a closed valley. Please call Calgary on (403)829-1661 if you would like to explore this topic further. Thank you for reading our post.

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Roof Structure with Gable Ends and Valleys: Image KDS444 BY CC 3.0

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