Today we wrap up our three-week tenure on roofs with a few tips on how to get the most out of your asphalt roofing shingles.
Why so much talk about roofing? Because a roof in poor condition is to a home what Dion Phaneuf is to a defensive corps of professional hockey players.
Essentially, the potential for damage is extreme, with an aged roof eventually springing up leaks faster than Dion’s ability to cough up pucks in his defensive zone.
So, realizing that maintaining a home free from the damaging effects of water infiltration starts with your roof, we need to do all we can to ensure the long term success of our roof investment. Remembering that every layer of shingles represents one 1965 Pontiac Parisienne parked unnecessarily on your rooftop, if you’re redoing a roof’s surface, we start by removing every layer of existing shingles.
Next, fiberglass asphalt shingles need to be nailed onto plywood. Spruce plywood, or an equivalent OSB (oriental strand board) roofing product, will provide the necessary stability, and are the only underlay materials suitable to support the more ridged fiberglass shingle. So, if the existing roof has been covered by 1×6 or 1×8 pieces of spruce lumber, cover these planks with a 3/8” plywood, or the 15/32” OSB product.
Next, and still on the theme of stability, create the proper environment for your fiberglass shingles by ensuring your attic is adequately vented. Basically, you want the surface temperature of your shingles to match that of the underlayment, or, that the air temperature in the attic, matches that of the exterior air. The only way to achieve this is by creating an effective draft whereby outside air will enter the attic space via the soffit, then exit through a vent, or series of vents, located near the peak of the roof.
Venting through the soffit is pretty straight forward, and requires no calculating, because the strategy is to simply insert Styrofoam baffles in between each truss.
The Styrofoam baffles get stapled to the roofing plywood, and are positioned so that they reach down into the soffit space, thereby preventing the attic insulation or blowing wool from blocking this key point of air entry.
The air exit strategy will be satisfied by a Maxivent. Maxivents are the not so attractive, chimney-like devices you see on most roofs these days. There are alternatives to the Maxivent, such as using ridge venting, or a series of smaller, slantback vents, or even solar power vents that operate with their own fans.
However, with no moving parts, and only one maxivent needed on most roofs, which means only one hole to cut out and seal, none of these alternative products can compare with the ease of installing, general efficiency, and long term viability of the Maxivent.
How to calculate your maxivent needs? One #301 Maxivent will service up to 1200 square feet of attic floor space, or meet the needs of your average 40’x30’ home. If you own a larger or smaller home, or have a garage or addition that requires venting, optional Maxivents include the #303 model (satisfies 800 sq. ft. of attic area) or the #302 Maxivent (satisfies 500 sq. ft. of attic floor space). Essentially, you can’t have too much ventilation, so if you’re not sure, go bigger.
Next, use a quality underlay felt. Your fiberglass shingles will require both an ‘ice + water shield’ product, used along the roofs edge, and in any valleys, along with a felt paper on the balance of the roof. ‘Ice + water shield’s’ are pretty standard, however, there’s a world of various felt coverings to choose from.
Recommendation? Avoid the paper felt, and buy the best synthetic felt available. A quality synthetic felt offers that key, secondary line of defence against water infiltration and ice dams.
Finally, if your home is situated in a wind tunnel, have your roofer follow the extra nails, extra caulking procedures related to better shingle tab adhesion.