Anacortes Roofing When people think about a roof, they picture shingles. Shingles are what you see from the street, and they matter for looks and wind resistance — but the parts of the roof that actually keep water out of your house are mostly hidden. Underlayment and flashing do the real waterproofing work. In a place like Anacortes, where salt air off the water, driving rain, and a long moss season put steady pressure on a roof system, those hidden layers deserve as much attention as the shingles on top of them.
Underlayment: The Roof's Backup Plan
Underlayment is the water-resistant layer installed directly on the roof deck, before shingles go down. Its job is to protect the plywood or OSB sheathing if wind-driven rain gets under a shingle, or if a shingle is ever lost in a storm. Think of it as the roof's backup plan — shingles are the first line of defense, underlayment is what stands between a small leak and a real problem.
- Traditional felt paper — the old standard. It works, but it can tear more easily during installation and doesn't handle repeated wet-dry cycles as gracefully over time.
- Synthetic underlayment — what we install as our standard on most roofs today. It's lighter, tougher underfoot, and more consistent in how it sheds water, which matters on the steep and often damp roofs common around Skagit County.
- Ice and water shield — a self-adhering membrane used at vulnerable spots like eaves, valleys, and around penetrations. It's not just for ice dams; in our climate it also guards against wind-driven rain backing up under shingles during winter storms off the Sound.
The right underlayment strategy depends on the roof's slope, the age of the deck underneath, and how exposed the home is to weather. A roof tucked among trees with heavy moss growth needs different attention at the eaves than an open roof catching the full brunt of a southwesterly storm.
Flashing: Where Roofs Actually Fail
If you ask a roofer where leaks really start, the honest answer is almost never "in the middle of a shingle field." It's at the transitions — where the roof meets a wall, a chimney, a skylight, a vent pipe, or another roof plane. That's flashing's job: metal or formed material installed at those transitions to route water around the gap instead of letting it soak in.
Common flashing types on local homes
| Flashing type | Where it's used | Why it matters here |
|---|---|---|
| Step flashing | Where a roof slope meets a sidewall | Interleaved with each shingle course so wind-driven rain can't work its way sideways under the siding |
| Valley flashing | Where two roof slopes meet | Valleys carry the heaviest water volume during Skagit County downpours and need a clear path |
| Chimney and skylight flashing | Around penetrations through the roof plane | A frequent leak point if the original flashing was undersized or has corroded |
| Drip edge | Along eaves and rakes | Directs water off the roof edge instead of behind gutters or into fascia boards |
Flashing is almost always metal — usually galvanized steel or aluminum. That's where our salt-air environment comes into play. Homes closer to the water see faster corrosion on unprotected or lower-grade metal flashing than homes further inland. Over years, corroded flashing can develop pinholes or lose its seal at seams, and by the time a stain shows up on a ceiling, the damage has often been building for a while.
Moss Season and What It Does to These Systems
Anacortes and the rest of Skagit County get a long, wet moss season, and moss doesn't just sit on top of shingles looking bad. As it spreads, it holds moisture against the roof surface far longer than open air would, and its root structure can work into shingle edges and lift them slightly at the tabs. That lifted edge is exactly where wind-driven rain finds its way to the underlayment below. Moss growing in a valley or against a flashing seam is often the first sign that water isn't draining the way it should.
Regular moss removal — done carefully, without pressure-washing granules off the shingles — and keeping gutters and valleys clear are simple habits that protect the flashing and underlayment underneath, not just the shingles on the surface.
Why This Matters More Than Brand Choice
Homeowners often research shingle brands and colors in detail, which makes sense — that's the visible decision. But two roofs with identical shingles can perform very differently depending on how the flashing was detailed and what underlayment sits beneath them. A roof with excellent shingles and poorly lapped step flashing will leak before a roof with modest shingles and correctly installed flashing ever does. This is also why roof inspections and repairs should always look past the shingle layer — a leak at a chimney or valley is rarely solved by patching shingles alone if the flashing underneath is the actual source.
What to Ask About on Your Own Roof
- What underlayment is specified, and is ice and water shield included at eaves, valleys, and penetrations?
- What type and gauge of metal is used for flashing, and how is it treated for a coastal, salt-air environment?
- How is step flashing integrated with the siding at sidewalls, rather than just caulked over?
- Is there visible moss, and is it concentrated in valleys or against flashing where drainage matters most?
If you're not sure what's happening beneath your shingles — or you've noticed moss buildup, a stain on a ceiling, or a roof that's simply getting older — we're happy to take a look. Reach out for a free, no-pressure estimate and we'll walk you through what we find, in plain terms, with no obligation to move forward.