What is the best underlayment for a roof replacement in NB's climate?

For New Brunswick's demanding climate, synthetic underlayment is the best choice for most roof replacements, offering superior tear resistance and moisture protection compared to traditional felt paper. Ice-and-water shield membrane along the eaves and valleys is essential, not optional, given NB's severe ice damming conditions.

Synthetic underlayment costs $0.50-$0.80 per square foot compared to $0.25-$0.40 for felt, but the performance difference justifies the investment in NB's harsh conditions. Products like GAF Deck-Armor, Owens Corning ProArmor, or CertainTeed RoofRunner offer excellent tear resistance during installation and superior water resistance if shingles are damaged by ice or wind. These synthetic products won't wrinkle, tear as easily during installation, or deteriorate from UV exposure if the roof project extends over multiple days.

Ice-and-water shield membrane is absolutely critical along NB's eaves, typically extending 3-6 feet up from the roof edge depending on your home's overhang and local ice damming history. This self-adhering membrane creates a watertight seal around nail penetrations and prevents ice dam water from infiltrating under shingles. In areas with severe ice damming (Saint John River valley, Bay of Fundy coastal communities), many contractors extend ice-and-water shield coverage further up the roof slope for additional protection.

NB's 100+ annual freeze-thaw cycles and heavy snow loads (200-300+ cm annually) make underlayment durability crucial. Traditional felt paper can deteriorate quickly when exposed to these temperature swings, especially if roof installation is delayed by weather. Synthetic underlayment maintains its integrity through temperature extremes and provides better temporary weather protection if shingle installation is interrupted.

Valley protection requires ice-and-water shield extending at least 12 inches on each side of the valley centerline. NB's heavy snowmelt and ice damming concentrate water flow in valleys, making this one of the most vulnerable areas for leaks. Some contractors recommend full synthetic underlayment coverage on complex roof designs with multiple valleys, dormers, or steep pitch changes.

Seasonal timing affects underlayment choice in NB. Synthetic underlayment provides better temporary weather protection during spring and fall roof replacements when sudden weather changes are common. If you're replacing your roof during NB's prime roofing season (June through September), either option works well, but synthetic still offers installation advantages in windy conditions common along the coast.

For metal roofing installations, high-temperature synthetic underlayment is essential since metal roofing can reach much higher temperatures than asphalt shingles. Standard felt paper can deteriorate under metal roofing, while synthetic products are designed for these temperature extremes.

Budget considerations: Adding synthetic underlayment and proper ice-and-water shield coverage adds $500-$1,200 to a typical NB roof replacement, but this represents excellent insurance against ice dam damage that can cost thousands to repair. Given NB's climate challenges, skimping on underlayment is false economy.

Always ensure your roofing contractor understands NB's ice damming conditions and includes adequate ice-and-water shield coverage in their quote. A contractor who suggests minimal eave protection doesn't understand Maritime winter conditions.

Need help finding an experienced roofing contractor familiar with NB's climate challenges? New Brunswick Renovations can connect you with local professionals who understand proper underlayment selection and installation for Maritime conditions.