Valleys can be a particular problem for your roof. Forming a valley where two parts of your roof come together, it not only needs to direct rainwater down to the edge of your roof, it also must keep water coming from one side of the roof from splashing up under the shingles on the other side.
But what's the best product to use when you want to prevent leaks in your valleys? Let's compare three popular options.
Ice and Water Shield
An ice and water shield is a membrane that adheres to your roof in the valleys. Typically about three feet wide, it provides excellent protection when ice or water gets under the shingles. Once the water is under the shingle it will run down on top of the ice and water shield and exit at the eve of the roof. This means you're able to simply lay down a membrane and continue roofing as usual, though some conditions will require the addition of metal flashing on top of the membrane.
Metal flashing is a long, sheet of thin metal, typically aluminum or steel, which protects the valley from water infiltration, metal valleys are usually used when roofing with shingles ,slate, cement, tile and thick dimensional shingle that are thick and don’t conform well to the valley. Though you can use metal flashing on its own in a valley, the best practice is to lay metal flashing over the top of the ice and water shield, providing extra durability and insurance and helping keep your roof watertight.
SIS Asphalt roll roofing (Double Coverage Roll Roofing)
You can also line your valley with double coverage granual roll roofing material. Though this has been a common practice in the past, it’s an outdated process and hardly ever used.
Now that you know the different approaches to waterproofing your roof's valleys, it's time to talk to a contractor. At CRS we’ll help you identify the best underlayment and roof solution for you. Contact us to get started.