Asphalt Shingle Roofing in Concrete for a Roof That Stays Wet

Why are asphalt shingles so common on Skagit valley homes?

Because they are the most affordable covering in published Washington cost guides, every roofer installs them, and spot repairs are easy. They suit a wide range of roof pitches, and parts and matching shingles are widely available. Their weakness is moisture, which the valley has in large amounts.

Availability matters in a rural area. A roofer can bring bundles in one trip and finish a repair without a special order. That is harder with slate or cedar, and with metal it needs panels cut to length.

None of this makes asphalt a bad choice for a wet climate. It means the roof needs good ventilation, clear valleys and gutters, and a plan for moss. The guide on metal or shingle roofs compares the two in the weather these towns get.

What does moss do to asphalt shingles?

Moss holds moisture and debris against the roof and can lift shingle tabs, according to Oregon State University Extension. Over time the lifted tabs let water in. Moss does not always kill a shingle, but it shortens its useful life and gives rain a path under the courses.

Removal needs care. The same extension guidance warns that pressure washing can damage shingles, stripping granules and driving water under the tabs. Zinc strips or treatments are common, but OSU cautions against zinc on roofs with copper gutters or flashing.

How many layers of shingles can a roof have?

It depends on local building rules, which this site cannot state for your address. Some Washington cities, among them Sammamish and Enumclaw, cap composition roofing at two layers. A second layer also traps heat and hides the deck, so many roofers prefer a full tear-off. Ask the building department.

Ask the roofer to confirm how many layers exist before quoting, and what the quote assumes. On older houses around Darrington, where a mill-era home may already have been re-covered, the count is often a surprise.

The county or city building department sets the rule where you live. The permit guide lists what to ask in each county.

What should be in an asphalt shingle quote?

The shingle line by name, the underlayment, the flashing, ventilation, tear-off and disposal, an allowance for rotten decking, and the cleanup. A quote that lists only squares and labor leaves out the parts where shingle roofs actually fail. Ask the roofer to itemize and put it all in writing.

Check that the quote follows the manufacturer's installation instructions, because some warranties depend on it. Ask who is on the roof and whether the crew is employed by the contractor. Verify the roofer's registration with the Department of Labor & Industries before signing, using the steps in the registration guide.

How does a shingle roof cope with shade and heavy rain together?

Reasonably, if three things are right: the underlayment and flashing keep water out when shingles are soaked, the attic is ventilated so the deck can dry from below, and the surface is kept clear of needles and moss. When any one fails, a shaded slope ages far faster than a sunny one.

Shade slows drying, and a shingle that never fully dries absorbs a little more water each season. The granule layer wears, algae takes hold and edges soften. Roofs on the north side of a house under tall trees often look ten years older than their south-facing neighbors.

If the lot is heavily shaded, ask the roofer about algae-resistant lines, about trimming back branches, and about how the attic will be vented. Those choices matter more here than a small difference in shingle grade.