Roof Installation
Six nails, not four. The wind ratings printed on a shingle wrapper — ASTM D3161 Class F at 110 miles per hour, ASTM D7158 Class H at 150 — are earned in a laboratory with six fasteners per shingle. A standard installation uses four. If your roof is going on in a high-wind region, or the manufacturer's enhanced coverage is part of why you chose that product, the six-nail pattern is not an upgrade to negotiate. It is the condition the number depends on, and it costs a few dollars a square.
A roof is an assembly, not a covering
The visible material is one layer in a stack that only works whole: drip edge at eaves and rakes, a water barrier where ice or wind-driven rain will push hardest, underlayment across the field, a starter course anchoring the first row, formed metal flashing at every wall, chimney, skylight and vent, valleys detailed to carry two slopes at once, then the covering, then ridge and vents. Substitute sealant for a formed piece of metal anywhere in that list and the roof has a countdown on it from day one.
Drip edge is not optional
Residential code requires it at eaves and rakes, lapped and extended past the sheathing so water leaves the edge instead of curling back onto the fascia. It is one of the cheapest components on the roof and one of the most commonly left off older work. The roof assemblies chapter of the residential code sets out the requirement along with fastening and underlayment minimums.
The ice barrier goes further than people expect
Where ice forms along eaves, the barrier has to run from the roof edge to at least twenty-four inches inside the exterior wall line — measured horizontally, from the wall, not from the gutter. On a low-pitched roof or one with a deep overhang, meeting that means well more than a single course of membrane, which is exactly why it gets short-changed on cheap bids.
Ventilation is a ratio, not a vibe
The rule of thumb has a number behind it. Code asks for net free ventilating area of at least one square foot for every 150 square feet of attic floor. That can be halved to one in 300 where a vapour retarder is installed on the warm side of the ceiling, or where at least 40 percent of the vent area sits in the upper portion of the space with the rest low at the eaves. Note what that means in practice: the 1:300 allowance is earned by balancing intake and exhaust, so adding ridge vents without opening up soffit intake does not get you there. The roof and ceiling chapter carries the full text.
How the day is sequenced
Good crews stage material to reduce carrying, work in weather windows rather than against them, and dry in the exposed deck as they go so an afternoon storm never reaches a ceiling. Nothing gets opened wider than can be closed again before the light goes.
New builds and additions
New construction has its own rhythm — the roof has to be on before the interior trades can start, so scheduling matters as much as craft. Additions bring the harder problem: tying new work into an existing roof so the seam is both invisible and watertight. Matching an aged material exactly is rarely possible, and a blend that will read as a patch from the street should be disclosed before the order goes in, not after it is nailed down.
What to ask to see
Ask for the specification covering the layers you will never look at again — nailing pattern, underlayment type, ice barrier extent, which flashings are new rather than reused. That page, not the shingle colour, is where the quality of a roof is actually decided.
