Home / Roof Replacement
Seattle receives roughly 37 inches of rain a year. Houston gets about 50. New York City gets around 47. On paper, Seattle is the driest of the three. Yet roofs here fail earlier and in stranger ways than roofs in either of those cities, and the reason has nothing to do with how much water falls.
It is how long the roof stays wet. Seattle spreads that 37 inches across roughly 150 days of measurable precipitation, most of it arriving between October and May as drizzle, mist, and light steady rain rather than heavy convective downpours. A Houston roof gets soaked and then bakes dry in a few hours. A Seattle roof in February may not fully dry for weeks at a time. Add low winter sun angles, a tree canopy that shades north and east slopes for months, and daytime highs in the mid-40s, and you get a roof surface that lives in a state of permanent dampness for half the year.
That single fact drives almost every replacement decision we make. It determines which underlayment we use, why we detail valleys and eaves the way we do, why moss is a design consideration and not an afterthought, and why the ventilation work that happens under the deck matters as much as the shingles that go on top of it. A roof specified for a dry climate and installed in Seattle is a roof that will underperform its warranty.
The single most common cost surprise on a Seattle re-roof has nothing to do with shingle brand or color. It is the decking.
A large share of Seattle's housing stock was built before 1950. Craftsman bungalows in Ballard and Wallingford, Tudor revivals in Mount Baker, and pre-war homes across Beacon Hill and the Central District were commonly sheathed with either 1x6 skip sheathing (spaced boards with gaps between them, originally designed for cedar shake, which needs airflow underneath) or 1x8 shiplap. Both were entirely appropriate for the materials of their era. Neither is a good substrate for modern asphalt composition shingles.
Asphalt shingles need continuous support and reliable nail holding. Roofing nails must either penetrate at least three quarters of an inch into the decking or fully through its thickness. Drive a nail into the gap between two skip-sheathing boards and it holds nothing at all. Drive it into a century-old board that has dried, cupped, and split along the grain, and it may hold today and let go in the first serious windstorm. This is why a roof can look flawless from the ground and still shed shingles in a November blow.
When we open an older Seattle roof and find skip sheathing, the correct fix is to overlay the existing boards with new sheathing, typically 7/16 inch OSB or half-inch plywood, creating a continuous nailable surface. On a 20 square roof that can add several thousand dollars. It is also not optional if you want the manufacturer's warranty to mean anything, because virtually every shingle warranty is conditioned on installation over an approved deck.
The honest version of this conversation happens before the tear-off, not during it. We inspect from the attic side where access allows, look for telltale board spacing at the eaves, and check the age of the structure against permit records. We tell you the likely decking scenario and price both outcomes, so a mid-project discovery does not become a mid-project renegotiation.
Material selection in Seattle is a durability question first and an appearance question second. Here is how the realistic options behave in a wet, mild, moss-friendly climate.
The default for roughly nine out of ten Seattle homes, and for good reason. Laminated architectural shingles carry 30 to 50 year limited warranties, handle our moderate wind loads well when properly nailed, and cost a fraction of the alternatives. The meaningful spec is wind rating: look for ASTM D7158 Class H rather than the lower Class D or G ratings. In exposed locations near open water — Alki, Magnolia bluffs, Sunset Hill, Fauntleroy — that difference is not marketing, it is the difference between tabs staying down and tabs lifting.
Historically correct for many Seattle homes and still required or strongly encouraged in some landmark contexts. It is also the material most punished by our climate. Cedar in the Puget Sound lowlands holds moisture, feeds moss and lichen, and commonly delivers 20 to 30 years rather than the 40 or more it might reach in a drier region. If you want cedar for architectural reasons, budget for active maintenance and understand you are buying appearance and authenticity, not longevity.
The best pure performer for this climate, and priced accordingly. Metal sheds water fast, gives moss almost nothing to anchor to, and routinely exceeds 50 years. Two Seattle-specific notes. First, near saltwater, fastener metallurgy matters: mixing incompatible metals invites galvanic corrosion, so stainless or compatible-alloy fasteners are not an upgrade, they are the spec. Second, metal amplifies rain noise in a city where rain is near-constant, which is a real quality-of-life consideration and worth discussing before you commit.
Seattle's density boom produced thousands of narrow-lot townhomes with flat or near-flat roof sections, concentrated in Ballard, Fremont, Capitol Hill, and along the light rail corridor. Asphalt shingles are not rated below a 2:12 pitch and should never appear there. Single-ply membrane is the correct assembly, and on these roofs the failure point is almost never the field of the membrane — it is the terminations, drains, and parapet details.
Traditional asphalt-saturated felt absorbs water and wrinkles when it does. On a job that gets rained on mid-installation — a routine occurrence eight months of the year in Seattle — those wrinkles telegraph through the finished shingle course as visible ripples and create small standing-water channels underneath. Synthetic underlayment does not absorb water, lies flat, and stays intact if weather forces a pause between tear-off and dry-in. In this climate the upgrade pays for itself in the first rainy install.
Seattle sits outside the classic ice dam belt, so code does not force ice-and-water membrane at the eaves the way it does in Minneapolis or Buffalo. That has been read by some contractors as permission to skip it. We disagree, for a specific reason: Seattle's freeze events are infrequent but not absent, and a single cold snap over a poorly ventilated attic produces exactly the melt-refreeze cycle that drives water backward under shingles. More routinely, wind-driven rain in a Puget Sound storm pushes water uphill under the first courses. Self-adhered membrane at eaves and in every valley is cheap insurance against the two failure modes this city actually produces.
Most roofs that leak are not leaking through the field of the shingles. They are leaking at a transition — a chimney, a skylight, a dormer wall, a plumbing vent, the point where a lower roof meets a vertical wall. Step flashing must be woven course by course, not run as a single bent length caulked at the top. Kickout flashing at the base of a roof-to-wall junction is one of the most frequently omitted components in residential roofing and one of the most destructive when missing, because the water it fails to redirect goes directly into the wall cavity and siding rather than into the gutter, where it does damage that stays invisible for years.
Ventilation is where a lot of Seattle roofs quietly fail from the inside. Code generally requires one square foot of net free ventilating area per 150 square feet of attic floor, or a 1:300 ratio when a balanced system places 40 to 50 percent of the venting in the upper portion. The word doing the work in that sentence is balanced. Intake at the soffits and exhaust at the ridge must be paired. Adding a ridge vent to a house whose soffit vents are painted shut or stuffed with insulation does not improve airflow; it can pull conditioned air up out of the living space instead. In a mild wet winter, an under-ventilated attic accumulates condensation on the underside of the deck, which rots sheathing from below while the shingles above look perfectly healthy.
Washington adopts the International Residential Code with state amendments, and the City of Seattle Department of Construction and Inspections administers permitting inside city limits. Two points matter to homeowners.
First, the layer limit. Code permits a maximum of two layers of asphalt shingles on a structure. If your roof already carries two layers, a third is not an option regardless of what anyone quotes you. Beyond legality, a roof-over of any kind hides the decking, traps a layer of moisture between assemblies, adds dead load, and prevents anyone from finding the rot that may already be underway. In this climate we recommend full tear-off in nearly every case, and we will tell you plainly when a roof-over is the wrong call even though it would be the cheaper invoice.
Second, permits. Roof replacement in Seattle generally requires a permit, and structural work such as sheathing replacement clearly does. We pull permits as part of the project rather than leaving it to the homeowner, because an unpermitted re-roof surfaces later at exactly the worst moment: during a sale, in a disclosure, or in an insurance claim after a storm.
Most Seattle single-family asphalt composition re-roofs land between $9,000 and $22,000. That range is wide because roofs are not priced by square footage alone. These are the variables that actually move it:
Anything steeper than roughly 7:12 requires staging, harnesses, and slower work. Labor hours rise sharply, and many older Seattle homes have steep pitches by design.
Tear-off labor and disposal scale with layer count. Two layers is roughly double the debris volume and tipping cost of one.
The largest single swing factor. Sound plywood adds nothing; skip sheathing overlay or widespread rot repair can add thousands.
Every chimney, skylight, dormer, and vent is a hand-detailed flashing assembly. A complex roofline costs more than a simple gable of equal area.
Narrow lots, steep driveways, tight alleys, and mature landscaping to protect all add setup time. Common on Queen Anne, Magnolia, and older Ballard lots.
King County transfer station tipping fees are a real line item, not a rounding error, particularly on multi-layer tear-offs.
We give a fixed written quote after walking the roof in person and looking at the attic where access allows. A phone estimate or a satellite measurement cannot see decking, cannot see ventilation, and cannot see the rot at the bottom of a valley. Those are precisely the things that determine the price.
Code limits, dead load math, warranty consequences, and why the 15 to 25 percent saved today is usually erased at the next replacement.
How asphalt, cedar, standing seam metal, composite, and membrane actually perform in a wet, mild, moss-heavy climate.
Skip sheathing, condensation rot, plywood versus OSB, and how to keep decking from becoming an open-ended charge.
Most Seattle single-family asphalt composition re-roofs run between $9,000 and $22,000. The range is driven by square footage, roof pitch, how many existing layers must be removed, decking condition, and the number of chimneys, skylights, and vents that require hand-detailed flashing.
Most single-family re-roofs finish in one to three working days. Steep pitches, multi-layer tear-offs, complex rooflines, and decking replacement extend that timeline.
Roof replacement in Seattle generally requires a permit, and structural work such as sheathing replacement clearly does. We pull permits as part of the project rather than leaving it to the homeowner.
Code allows a maximum of two layers of asphalt shingles. Even where a roof-over is technically legal, we recommend full tear-off in nearly all Seattle cases because a roof-over hides the decking, traps moisture between assemblies, adds dead load, and prevents anyone from finding rot already underway.
Almost always because of decking. Many pre-1950 Seattle homes were built with skip sheathing or shiplap that cannot properly hold modern shingle nails and must be overlaid with new sheathing. We inspect for this before tear-off and price both scenarios up front so it is not a mid-project surprise.
Standing seam metal, comfortably. It sheds water fast, gives moss almost nothing to anchor to, and routinely exceeds 50 years. Architectural asphalt composition remains the value choice at 30 to 50 year warranties, while cedar shake typically delivers 20 to 30 years here because our climate feeds moss and holds moisture in the wood.
We measure in person, walk the roof, check the attic, and give you a written fixed quote — not a satellite guess.
