Roof Valley Flashing and Their Common Problems

With regards to roofing problems, valleys are probably the most inconvenient regions. At the point when you consider the enormous volume of rain and snow that is diverted through roofing valleys, it’s not difficult to perceive how all that wear and tear can prompt leaks.

Most common problems with roof valleys flashing

Here are the most common problems with roof valleys along with solutions to help you fix leaks or stop them before they start. 

Worn Underlayment

At the point when leaks crop up around roof valleys, the issue is frequently with the underlayment. Roof valleys face the elements – like rain, snow, ice, and debris – than some other part of the roof. On an asphalt shingle roof, untrained builders or at times pick roll roofing as the valley underlayment. Since roll roofing has about a 10-year life range, the valleys will begin to get damaged long before the shingles reach their lifespan.

There are several better approaches to move toward valley underlayment. A few builders will decide to use two layers of roll roofing, however the better option, regardless of whether your roof is shingle or another material, is to use flashing as the valley underlayment. Pick 26-gauge or thicker galvanized steel – or another non-corrosive metal that won’t stain the roofing – as the valley underlayment, and it will keep going at any rate as long as the actual roof. 

Thermal Expansion and Incorrect Sizing 

Another significant issue is thermal expansion. In a warm climate, the valley underlayment will expand, and as it does, it might wrinkle. If you’ve installed metal valley underlayment, those wrinkles can prompt holes, cracks, or tears, and the actual wrinkles can turn out to be adequately enormous to divert the flow of water under the roofing material. 


To keep harm from thermal expansion, your roofing contractor install the valley underlayment in little sections. Ensure each piece is a few feet wide and not more than eight to 10 feet. Bigger pieces of underlayment will expand farther than smaller ones, which makes them considerably more prone to wrinkle or buckle. 

READ MORE:  Types of Roofing Sealants and Best Sealants for Asphalt Shingles

Snow and Standing Seams 

In regions that get a great deal of snow, valleys in a standing roof can be dangerous. Since the flow of the valley doesn’t ordinarily run in a similar direction as the standing seams, huge lumps of snow and ice flowing down the valley could damage the seams. This diminishes the strength of the seam as well as may harm the crease enough to cause a hole. 

Luckily, the solution to this issue is simple. Use snow gatekeepers to keep huge lumps of snow and ice out of your roof’s valleys 

Cross Wash 

Cross wash happens when the volume of water flowing into a valley is enormous enough that, rather than flowing down the valley, it washes up the opposite side of the valley and under the roofing material. This is another simple issue to address. Start by guaranteeing that the roofing material is appropriately attached along the edges of the valley. If all else fails, use sealant where the roofing material joins the valley underlayment to stop any leaks caused by cross wash. 


Generally, leaks and other problems common to roofing valleys are not difficult to address. Settle on the correct choices with regards to flashing and valley underlayment, and you will curb most problems before they start. Now and again, additional means like sealants or snow watchmen will forestall further problems or right a current hole. 

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