What's the right way to install ice and water shield on a low-slope roof section in Campbellton where we get heavy ice buildup?

On a low-slope roof in Campbellton, ice and water shield (IWS) isn't just recommended — it's your primary line of defence, and it needs to cover the entire roof surface, not just the eave zone.

Campbellton sits in one of New Brunswick's snowiest corners, regularly pulling 350–400+ cm of snow annually, and the Restigouche valley's temperature swings create brutal freeze-thaw cycles that destroy improperly protected low-slope roofs fast. Here's how to do it right.

Coverage is everything on low-slope sections. The National Building Code of Canada 2020 (adopted in NB effective May 1, 2025) requires IWS to extend from the eave to a point at least 900mm (36") inside the interior wall line on all roofs — but on a low-slope section (anything under 1:6 pitch, roughly 2-in-12), that minimum is dangerously inadequate for Campbellton conditions. Industry best practice — and what any experienced roofer in northern NB will tell you — is to run self-adhering IWS across the entire low-slope area, wall to wall, ridge to eave. No gaps, no exceptions.

Substrate prep makes or breaks the install. The deck needs to be clean, dry, and free of frost — which in Campbellton means your installation window is genuinely May through September. IWS adhesive won't bond properly below about 5°C, and if you're trying to stick it to a deck that had frost on it two hours ago, you're wasting material. Sweep the deck, nail down any loose sheathing, and if you're working over old OSB with surface degradation, prime it with a compatible asphalt primer and let it fully tack before rolling out the membrane.

Overlap and sealing details matter enormously. Run your first course starting at the eave, leaving a 10–15mm overhang into the drip edge or gutter. Each subsequent course overlaps the one below by a minimum of 150mm (6") on horizontal seams, and 300mm (12") on vertical end laps — roll those seams hard with a J-roller or seam roller to eliminate any air pockets. At valleys, run a separate strip of IWS up each side of the valley before your field courses, minimum 500mm wide on each side. At penetrations — vents, skylights, chimneys — cut the IWS to wrap up the vertical surface at least 150mm and seal with compatible flashing tape or roofing caulk.

The transition to your steep-slope section is where a lot of roofs fail. Where the low-slope membrane meets a steeper section, the IWS should run up and under the steep-slope underlayment by at least 300mm. Lap it properly so water always sheds over the top of the lower layer — never under it.

For a low-slope application in Campbellton specifically, a two-ply approach is worth serious consideration: a base layer of IWS followed by a quality modified bitumen cap sheet (torch-applied or cold-applied depending on your contractor's setup). This gives you redundancy against the ice damming and wind-driven rain that Campbellton sees regularly. A single layer of IWS under shingles is fine for steep slopes, but on low-slope sections it's working much harder.

This is professional territory. Low-slope roofing is a different trade skill set from standard asphalt shingle work — torch-applied membranes require a licensed roofer and fire watch protocols, and improper installation voids manufacturer warranties fast. For your permit, contact RSC 2 — Restigouche at (506) 789-2595, as Campbellton's surrounding rural areas fall under their jurisdiction. If you're within the City of Campbellton limits, contact the city's building department directly — check bathurst.ca for regional contacts or the city's own website for current permit office details.

Browse roofing contractors serving the Campbellton area in the New Brunswick Construction Network directory — look specifically for contractors with low-slope or flat roofing experience, not just general roofers.