Mike Holmes: Get insane about your membranes
Exterior walls, foundation and roof require expert waterproofing against the elements:
Waterproof membranes should wrap around windowsills and door jambs to fully protect a home’s exterior against leaks, which means applying it before windows and doors are installed.
Photograph by: Holmes Group
Mike Holmes offers advice about membranes so that exterior walls, foundations and roofs have expert waterproofing against the elements. One of the most important systems that protect your home are waterproof membranes. When they don’t work or get compromised, fixing the problem and repairing the damage can be very extensive, not to mention expensive.
Since they are meant to stop outside water and moisture from getting in, it makes sense that waterproof membranes are part of your home’s building envelope — what separates the inside of your home from the outside. Foundation An exterior waterproof membrane on your home’s foundation is literally an extra layer of protection.
There are two types: damp-proof and waterproof, and they do different jobs. A damp-proof membrane is usually a black tar or asphalt compound that gets painted or rolled onto your typical concrete foundation. Then over top of that goes a mastic coating — which is like a waterproof paste — a mesh coating and then another layer of mastic. This system is meant to stop vapour from penetrating through the concrete — water vapour and sometimes even radon gas. But it’s not 100-per-cent waterproof. Instead, I like a two-coat liquid rubberized membrane that’s sprayed on by certified contractors. It sets into a rubbery coating that is 100-per-cent waterproof.
But no matter what type of coating a foundation has, it must also be protected by dimpled membrane. Exterior walls Most exteriors — whether made of brick, aluminum, vinyl, wood or stucco — will allow some moisture to get in. If that moisture meets the exterior sheathing underneath, there’s the potential for mold. To protect the exterior sheathing, we wrap it with house wrap or moisture wrap. Tyvek or Typar are the most popular with builders. Both are a type of synthetic wrapping material that has tiny microscopic holes, so they are still breathable. But for this waterproof system to work, it must be properly installed. That means Tuck Taping all the joints and seams. If not, water can get in behind it, which defeats the purpose.
The roof: All roofs need some kind of sheathing membrane on them to control and drain moisture that might penetrate your roof. Today’s products do a better job at stopping moisture than the tarpaper of the 1980s. Self-adhering products like ice and water shield are better. They prevent ice damming and make the installation process easier — which cuts down on labor time, saving the homeowner some money. Also, when you nail shingles over tarpaper it leaves holes in the surface. This makes the membrane weaker. But when you nail shingles over self-adhered roofing underlayment, such as Blueskin house wrap, the adhesive closes up around the nail, so there are no holes or gaps in the membrane. Blueskin also makes a “high-temperature” product specifically for metal roofs. It has a higher melting temperature than regular ice-and-water membranes. Why? Because a metal roof gets very hot in the summer. It’s important to make sure the adhesive on the membrane doesn’t melt.