Roof Installation: A Step-by-Step Guide to the Process
A roof installation is one of the biggest investments you'll make in your home, and most homeowners have no idea what actually happens between the day the old shingles come off and the day the crew packs up. That gap in knowledge leads to rushed decisions, surprise costs, and contractors who skip steps you'd never notice until the first heavy rain.
This guide walks you through the entire installation process, from tear-off and deck inspection to underlayment, flashing, and final shingle courses. You'll see what separates a rushed job from one built to last 25 to 30 years, and where material choices actually matter versus where they're just upsells.
We wrote this for Kirkland, Bellevue, and Seattle-area homeowners deciding between a DIY weekend project and hiring a licensed crew, and for anyone comparing quotes for new construction roof installation. By the end, you'll know exactly what questions to ask, what a fair timeline looks like, and why a locked-in price quote protects you far better than a low estimate that grows once the tear-off starts.
What to know before your roof installation begins
Getting the timing right matters more than most homeowners realize. In the Pacific Northwest, weather windows are tight: contractors generally avoid tear-offs between late October and March because exposed decking can't sit under an open sky if a system rolls through. Book your roof installation for the dry stretch between April and September if you have any flexibility, and expect a 5- to 10-day lead time even with a good crew, longer during peak summer months when everyone's calendar fills up.
Permits are non-negotiable in most Washington cities, including Kirkland, Bellevue, and Redmond. A licensed contractor pulls the permit for you and schedules the required inspections, but if you're managing the installation of roof work yourself, you'll need to visit your city's building department, submit plans showing the roofing system and ventilation, and pay a fee that typically runs $200 to $500 depending on square footage. Skipping this step isn't just risky, it can void your homeowner's insurance if a claim ever traces back to unpermitted work.
A roof installed without a permit is a roof your insurance company can walk away from when you need it most.
Choosing your roofing material
Material choice drives both your budget for a new roof in 2026 and how long you'll go before doing this again. Asphalt shingles remain the default for a reason: they're affordable, install fast, and hold up well in Western Washington's wet, moderate climate. But metal, cedar shake, and composite options each solve different problems, and it's worth knowing whether metal or shingles pay off long-term.
| Material | Typical Lifespan | Relative Cost | Best For | |---|---|---| | Asphalt (3-tab) | 15-20 years | $ | Budget-conscious replacements | | Architectural shingles | 25-30 years | $$ | Most Kirkland-area homes | | Standing seam metal | 40-50 years | $$$ | Long-term owners, steep pitches | | Cedar shake | 25-30 years | $$$ | Historic or high-end aesthetics |
DIY versus hiring a licensed crew
A weekend DIY tear-off and reroof sounds appealing until you factor in the real risks. Roofing is the most dangerous trade in residential construction according to OSHA injury data, and a single missed step in flashing or underlayment can cause leaks that take years to show up and thousands to repair. Most manufacturers also void shingle warranties if the installation isn't performed by a certified installer, which erases one of the biggest financial protections you're paying for.
On the other hand, hiring a roof installation pro near you brings crew coordination, dump trailer logistics, and manufacturer certifications that a solo homeowner can't easily replicate. Before you sign anything, ask every contractor bidding your job these questions:
Are you licensed and bonded in Washington State?
What's included in your written, locked-in quote, and what triggers a change order?
Who's responsible for disposal and dump fees?
What warranty do you offer on labor, separate from the manufacturer's material warranty?
How many crews will be on-site, and how long will the job actually take?
What a fair quote should include
One of the biggest sources of homeowner frustration is a quote that balloons once tear-off starts and the crew finds rot or inadequate ventilation. That's exactly why Legacy Exteriors uses a locked-in price quote on every project: the number you sign is the number you pay, barring changes you approve in writing. Before work begins, your quote should spell out material brand and grade, underlayment type, ventilation upgrades, flashing details, and a firm start and completion date, not just a lump-sum total, and you can run your own roof cost estimate first to see whether the number is in range.
Step 1. Remove the old roof and inspect the deck
Every legitimate roof installation starts with a full tear-off, not a layover of new shingles on top of old ones. Crews strip existing shingles, felt paper, and old flashing down to bare decking, then haul debris to a dump trailer staged in your driveway. Expect this stage to take a full day on an average 2,000-square-foot roof, longer if there are multiple layers of old roofing or steep, cut-up rooflines that slow the crew down and stretch how long the whole reroof takes.
Once the deck is exposed, the real inspection begins. A good crew walks every square foot looking for soft spots, delamination, or water staining on the underside of the plywood or OSB sheathing. This is the step that separates a durable installation of roof components from one that fails early, because nailing new shingles over compromised decking just hides a problem that will resurface as a sag or a leak within a few years.
A roof is only as strong as the deck underneath it, and you can't judge that deck until the old shingles are gone.
What deck damage actually looks like
Rotted decking isn't always obvious from the ground, which is exactly why tear-off matters. Look for these signs during the inspection phase:
Dark, soft, or spongy spots when the crew presses on the sheathing
Delaminated plywood layers separating like a stack of wet cardboard
Nail heads that pull through the wood instead of holding firm
Daylight visible through gaps once felt paper is removed
Musty odor coming from the attic side of the deck
Any section showing these signs gets cut out and replaced with new plywood or OSB, typically in 4-by-8-foot sheets matched to your existing deck thickness.
Why this step affects your final price
Deck replacement is the single biggest reason a roofing quote changes mid-project, and it's also where a locked-in price quote protects you. A fair contractor sets a per-sheet replacement rate upfront, usually $75 to $150 per sheet installed, so you know the cost before a single board comes up rather than negotiating while your roof sits open. Ask your contractor to photograph any damaged decking before replacement; reputable crews do this automatically as part of a documented roof inspection report, and it gives you proof if the issue ever comes up with your homeowner's insurance. Skipping photo documentation is a small red flag worth asking about directly.
Step 2. Install drip edge, underlayment, and flashing
With the deck inspected and repaired, the crew starts building the layers that actually keep water out. This stage is where cheap shortcuts hide easily, because once shingles go down, nobody can see whether the underlayment overlaps correctly or the drip edge was nailed at the proper spacing. Getting this right is the difference between a roof installation that sheds water for decades and one that leaks quietly behind the walls.
Shingles handle the wind and the sun, but drip edge, underlayment, and flashing are what actually stop water from getting in.
Drip edge and underlayment go on first
Drip edge installation starts with metal nailed along the eaves first, then the underlayment, then drip edge again along the rakes, overlapping it so water runs off the roof and not behind the fascia. Synthetic underlayment has mostly replaced felt paper on quality jobs because it resists tearing during installation and holds up better if a storm delays the shingle courses by a day or two, which is why it tops most lists of top underlayment options for shingle roofs. Along the eaves, in the first three to six feet where ice and snow can back up under shingles, crews install a self-adhering membrane like the GAF WeatherWatch leak barrier instead of standard underlayment, a step Washington's colder inland areas like Woodinville and Bothell benefit from even though coastal Seattle sees less snow.
Flashing details separate good crews from bad ones
Flashing gets installed at every point where the roof plane meets something else: chimneys, sidewalls, valleys, and skylights, and it's worth seeing how each flashing detail goes in. Bad flashing work is the single most common cause of roof leaks reported by inspectors, and it's almost always due to reused old flashing instead of new metal cut and bent to fit. New flashing should go in at every one of these locations on any legitimate reroof:
Valleys, where two roof planes meet and water volume is highest
Step flashing along chimneys and sidewalls, woven with each shingle course
Counter-flashing set into mortar joints or siding to shed water over the step flashing
Skylight curbs, where manufacturer-specific flashing kits are required
Pipe boots around vent stacks, using rubber or metal collars rated for your climate
Expect your contractor to walk you through each transition point before shingles cover it up, and ask for photos if they don't offer them. Once this layer is sealed and inspected, the roof is watertight even before a single shingle goes down, which is exactly the point.
Step 3. Add or replace roof vents
Before any shingles go down, the crew addresses attic ventilation, and this is a step a lot of budget bids skip entirely. Proper airflow keeps your attic close to outdoor temperature, which is why roof ventilation matters: it prevents ice damming in winter and stops shingles from cooking from underneath during summer heat. A roof installation without adequate ventilation can void your shingle manufacturer's warranty outright, since trapped heat and moisture accelerate granule loss and curling far faster than normal aging.
A roof without proper ventilation ages from the inside out, no matter how good the shingles on top look.
Balancing intake and exhaust
Good ventilation isn't just about cutting a hole at the ridge. It requires a balance between intake vents low on the roof, usually soffit vents, and exhaust vents high on the roof, which means choosing between ridge and box vents. Air needs to flow in at the eaves and out at the peak, carrying moisture and heat with it. If your existing setup only has exhaust with no matching intake, or vice versa, the crew should flag it and recommend a fix during this stage rather than after shingles are already down.
Vent Type | Location | Function |
|---|---|---|
Soffit vents | Eaves, underside of overhang | Intake, pulls in outside air |
Ridge vent | Peak of roof | Exhaust, continuous airflow along the ridge |
Box vents | Scattered across upper roof plane | Exhaust, used when ridge venting isn't feasible |
Power vents | Upper roof plane | Mechanical exhaust for problem attics |
What the crew actually does at this stage
On most reroofs, this step means cutting in a continuous ridge vent along the peak, removing outdated static vents that no longer meet code, and confirming soffit vents aren't blocked by insulation from inside the attic. If your home has a bathroom or kitchen exhaust fan venting into the attic instead of straight outside, a legitimate crew calls this out too, since it's a moisture problem no amount of roof ventilation can fully solve. Correcting it now, while the deck is still exposed, costs far less than tearing into a finished roof later. Ask your contractor directly whether your current ventilation is sized correctly for your square footage; most attics need roughly 1 square foot of vent area for every 150 square feet of attic floor, split evenly between intake and exhaust.
Step 4. Lay and nail the shingles
With ventilation sorted and the roof watertight underneath, the crew finally starts laying the shingles that actually give your roof installation its look and its wind rating. Work begins with a starter strip along the eaves, an adhesive-backed course installed upside down or purpose-built for the job, which seals the first row of visible shingles down and blocks wind from getting underneath the tabs. Skipping a proper starter strip is a cheap shortcut that shows up fast in the form of lifted shingles during the first real windstorm.
A shingle that isn't nailed in the manufacturer's nail zone isn't warrantied, no matter how good it looks from the driveway.
Getting the nailing pattern right
Each shingle has a manufacturer-specified nail zone, usually a horizontal band printed or embossed on the shingle itself, and every nail needs to land inside it. Nails placed too high miss the layer below and won't hold; nails placed too low, below the tab line, void the warranty outright because they're exposed to sun and water. A standard architectural shingle takes four nails, six in high-wind zones or on steep pitches above a 6:12 slope, and a good crew adjusts nail count based on your roof's exposure as they work through how asphalt shingles are laid course by course.
Nails driven flush, not overdriven through the shingle or underdriven above the surface
Four to six nails per shingle depending on wind zone and roof pitch
Each course offset from the one below so cutouts and joints don't stack in a straight line
Valleys woven or cut cleanly, matching whichever method the manufacturer specifies for that shingle line
Exposure kept consistent, typically 5 to 5 5/8 inches depending on the shingle style
Working the field of the roof
Crews typically work in sections, running courses up from the eaves toward the ridge on one roof plane before moving to the next, which keeps the pattern consistent and makes it easier to spot a misaligned course before it's covered by three more. Around chimneys, skylights, and sidewalls, shingles get cut and tucked against the step flashing installed in Step 2 rather than caulked over gaps, since caulk is a temporary patch, not a real seal. On an average 2,000-square-foot roof, this stage usually takes one to two days depending on crew size, roof complexity, and how many valleys and penetrations break up the field.
Step 5. Cap the ridge, clean up, and pass inspection
Once the field shingles are down, the crew finishes the roof by capping the ridge, the final seam where both roof planes meet at the top. Ridge cap shingles are thicker and pre-bent to fold over that peak, sealing out wind-driven rain that field shingles can't handle on their own. This step ties directly into the ridge vent installed in Step 3, since the cap shingles cover the vent slot while still letting air escape underneath. A properly capped ridge is one of the clearest signs of a professional roof installation versus a rushed one, because a crooked or gapped ridge line stays visible from the street for years.
The ridge cap is the last line of defense at the highest, most exposed point on your entire roof.
Cleanup matters more than homeowners expect
Debris left behind isn't just an eyesore, it's a safety hazard. A thorough crew runs a magnetic roller sweep across the yard, driveway, and any flower beds to pull up stray nails before pets, kids, or your car tires find them. They should also haul away the dump trailer, remove tarps protecting siding and landscaping, and walk the property with you to confirm nothing's left behind before they call the job done.
What the final inspection checks
Before your city closes out the permit, an inspector reviews the completed work against code, and your contractor should schedule this final inspection without you having to chase them down. A typical review covers:
Proper nailing pattern and shingle exposure across the field
Flashing at all valleys, chimneys, and sidewalls
Ventilation balance between intake and exhaust
Ridge cap installation and fastening
Overall workmanship consistent with the approved permit plans
Passing this inspection closes out your permit file and starts the clock on your manufacturer's warranty, so keep a copy of the report with your homeowner records.
Living with your new roof
A properly finished roof installation should give you decades of quiet performance, not phone calls about leaks or lifted shingles after the first storm. Now that you know what happens at every stage, from deck inspection through ridge cap and final inspection, you're equipped to hold any contractor's bid to that same standard, whether you're comparing quotes for a straightforward reroof or a new construction roof installation.
Keep your permit paperwork, warranty documents, and inspection photos together in one folder. You'll want them if you ever sell the house or file an insurance claim. Walk your attic once or twice a year to check for daylight, moisture, or musty smells, small signs that catch problems early instead of after they've spread into your decking.
If you're ready to see what a locked-in, no-surprises quote looks like for your home, get a free roof inspection in Kirkland, Bellevue, Redmond, or Woodinville from our crew today.
