When two sections of a roof meet with different heights or angles, it forms a depression known as a valley. This part of your home's roof is particularly prone to leaking due to the fact that it ends up channeling a lot of water during a heavy storm. If you're getting your roof replaced, ask your installers to use an ice and water shield membrane in the valleys to keep your home drier.
Stops Damage from Ice Dams
An ice dam occurs when snow or ice builds up on the roof, then starts to melt when heat from the rest of the home escapes into the attic to warm the surface. The water is trapped by the frozen material and soaks under the shingles instead of draining off. Roof valleys form ice dams more readily than the rest of the roof because the two roof slopes forming the sides of the valley tend to trap snow.
An ice and water shield is specially designed for dealing with these kinds of dams. Unlike plain roofing felt made with asphalt, this kind of membrane is rubberized to completely stop water from soaking through to the plywood sheathing below. Water that finds a way under the shingles hits the barrier and keeps running down the slope until it drops off the roof or gathers in the gutter.
Gets Better Coverage
Unlike other types of waterproof or water-resistant underlayments for roofing, an ice and water shield sticks to itself very well. This makes overlapping layers of the material very easy for the installers. It's also a breeze to create sealed corners without fasteners or special tools. This means you're a lot less likely to end up with small gaps in coverage that let water flow through.
Prevents Flashing Mistakes
Flashing made from sheet aluminum or steel is usually used as a waterproof barrier for sealing these valleys. However, it only takes one mistake during the installation of this metal layer to create a serious leak problem. Common valley flashing mistakes include:
- Attaching the material too tightly so it becomes warped when the temperatures change from season to season
- Installing narrow strips of flashing instead of a layer at least 18 inches wide
- Using too few fasteners or adhesives to anchor the flashing in place, leading to shifting
Installing a wide layer of ice and water shield underneath the metal flashing stops small mistakes from causing big leaks. Even the best roof installers can overlook a minor mistake when trying to build an entire roof, so an extra layer of protection is well worth the cost.
Eliminates Fastener Leaks
When you put a nail through a shingle or a layer of normal roofing felt, it creates a hole that can let water leak in and down to the attic unless you use self-sealing fasteners. Ice and water barrier seals itself when penetrated because of the rubber added to the blend. This is crucial because the installers attach both the flashing and shingle layers with numerous nails.
Aside from closing up around a nail, this type of underlayment also features a strong adhesive backing to keep it stuck to the roof sheathing. When installed over clean and dust-free wood, it seals to the surface without any other glues or nails. It's ideal for covering the unusual angles and slopes found in a roof valley.
Asking your roofing contractor to install ice and water shield in the valleys will raise your bill a little, but it's well worth the cost when it prevents costly repairs for water damage. Make this type of underlayment a part of your next new roof for reliability that lasts for decades.