Roof Installation Steps: What to Expect Start to Finish
A new roof is one of the biggest investments you'll make in your home, and most homeowners have no idea what actually happens between signing a contract and that final walkthrough, or how to pay for a new roof once they do. You see trucks pull up, hear hammering for a few days, and then it's done. But installation for roof projects follow a specific sequence, and knowing it helps you spot quality work from cut corners.
This guide walks you through exactly what happens during a professional roof replacement, from the first inspection to the final cleanup, and pairs with our overview of the roof replacement process and your options. We'll cover the roof installation steps in order: tear-off, deck inspection, underlayment, flashing, shingle or material installation, and ventilation checks. You'll know what your crew should be doing at each stage and why skipping steps causes leaks down the road.
Whether you're a Kirkland-area homeowner vetting a contractor's proposal or a hands-on DIYer weighing whether this is a project you can tackle yourself, this breakdown gives you the full picture. We've built roofs across Bothell, Woodinville, and Bellevue for years, and we're sharing the same process our crews use on every job, so you can hold your contractor to a higher standard and protect your home's investment.
What to know before your roof installation begins
Before a single shingle comes off your house, several things need to happen behind the scenes. Your contractor should pull the required building permit, check the extended weather forecast, and confirm your material order has arrived at the local supply yard. Skipping any of this creates delays or, worse, a crew working on your roof during a rainstorm because the schedule got tight. A solid installation for roof project starts with paperwork and planning, not with a truck showing up unannounced on a Tuesday morning.
A roof installed without a permit or a locked-in price is a roof you're gambling on.
Get your permit and timeline locked in
Most cities in the Kirkland, Bellevue, and Redmond area require a permit for a full roof replacement, and your Kirkland roofing contractor should handle this for you, not leave it on your plate. Ask for the permit number before work begins and confirm it's posted or available on request. Weather windows matter too: reputable crews won't tear off more roof than they can dry in before nightfall, especially in the Pacific Northwest where an afternoon shower can show up without much warning. Here's what a typical job timeline looks like based on roof size:
Roof Size (squares) | Estimated Install Time | Typical Crew Size |
|---|---|---|
Under 20 squares | 1 day | 4-6 installers |
20-35 squares | 1-2 days | 6-8 installers |
35-50 squares | 2-3 days | 8-10 installers |
50+ squares or complex roofline | 3-5 days | 8-12 installers |
Get a written timeline from your contractor before the crew shows up so you know what's normal and what's a red flag if things run long.
Pick your materials before the crew arrives
Having your shingle color, underlayment type, and ventilation components ordered and on-site before day one keeps the job moving. Nothing stalls a project like a crew standing around waiting on a material delivery. If you're comparing options, asphalt composition shingles remain the most common choice in this region, but standing seam metal roofing and synthetic slate are both worth a look if you're planning to stay in the house long term. Your contractor should walk you through the tradeoffs in cost, lifespan, and warranty coverage for each, including whether slate is worth the investment, and give you a locked-in price quote so the number you agreed to is the number you pay, regardless of what happens with material costs mid-project.
Protect your property and set expectations
Set up a walkthrough with your project manager the day before work starts to cover where materials will be staged, which paths trucks will use, and how your landscaping, siding, and gutters will be protected from falling debris. Tarps should go up around foundation plantings and any exposed windows near the roofline. Understand also that tear-off is loud and messy, dust and old shingle grit will end up in your yard temporarily, and a magnetic nail sweep should happen daily, not just at the very end. Knowing these details in advance means nothing that happens during the job catches you off guard.
Step 1. Tear off the old roof and repair the decking
Every legitimate installation for roof project starts with removal, not layering. Your crew should strip the old shingles, underlayment, and flashing down to bare wood, never install new material over an existing layer. Layering over old shingles might save a few hours, but it traps moisture, hides rot, and voids most manufacturer warranties. Watch for crews using tarps or a debris chute to catch old material as it comes off, keeping your yard and gutters clear of shingle grit and nails.
You can't judge the health of a roof deck until every old layer is off of it.
What tear-off actually reveals
Once the deck is exposed, your crew inspects every board for soft spots, water staining, and delamination. This is the moment that separates a rushed job from a careful one, because problems hiding under old shingles for a decade finally show themselves. Common issues include:
Soft or spongy plywood near valleys and chimneys, usually from long-term slow leaks
Discolored sheathing where old flashing failed
Gaps between deck boards on older homes with plank sheathing instead of plywood
Rusted or missing nails that need to be reset before new material goes down
Any board that flexes under foot pressure or shows visible rot gets replaced, no exceptions. Skipping this step to save time is one of the most common shortcuts homeowners never see, because it's covered up before the final inspection.
Decking repairs and what they should cost
Sensible contractors build a small decking allowance into your quote upfront, since most roofs need at least a few sheets replaced, and that allowance is part of what a roof replacement costs in 2026. Ask your contractor how they price additional decking beyond that allowance before work starts, not after the invoice arrives, and run the numbers yourself by estimating your roof's replacement cost first. A locked-in price quote should spell out exactly what's included so you're not stuck negotiating mid-project over a few sheets of plywood.
Decking Issue | Typical Fix | Ballpark Cost Add-On |
|---|---|---|
Minor rot, under 2 sheets | Spot replace plywood | $150-$300 |
Widespread soft spots | Replace 5+ sheets | $500-$1,200 |
Full deck replacement | Re-sheath entire roof | $2,000+ |
Think about the roof installation steps this way: everything that follows, flashing, underlayment, shingles, only performs as well as the deck underneath it. A solid deck is the foundation the rest of your new roof depends on, so this is not the stage to rush.
Step 2. Install the drip edge and underlayment
With the deck repaired and swept clean, your crew moves on to the parts of the roof most homeowners never think about but that do the real work of keeping water out. Drip edge and underlayment form the first line of defense against wind-driven rain, and getting this stage right matters more than the shingle color you picked. Rushing past it is exactly where a lot of cut-rate roof installation steps start to fall apart within a year or two.
Drip edge along the eaves and rakes
Metal drip edge gets nailed along the eaves first, then along the rakes, directing water off the roof and away from your fascia board instead of letting it wick back underneath. Skipping drip edge, or using it only on the eaves and not the rakes, is a shortcut that shows up later as rotting fascia and peeling paint. Ask your contractor which gauge and finish they use, since a flimsy aluminum strip bends and pulls loose far faster than a properly formed steel drip edge.
Drip edge is a five-dollar-a-foot detail that prevents a five-thousand-dollar fascia repair.
Underlayment: your roof's backup layer
Underlayment goes down next, covering the entire deck before a single shingle is laid. This layer is your backup plan if wind ever lifts a shingle or ice damming pushes water uphill under the surface material. Most jobs in our region call for one of these:
Underlayment Type | Best For | Notes |
|---|---|---|
Synthetic felt | Most standard roofs | Lighter, tears less than old felt paper |
Self-adhering ice/water shield | Eaves, valleys, low-slope sections | Required in ice-dam-prone areas |
Rubberized peel-and-stick | Skylight and chimney perimeters | Extra protection at penetrations |
Valleys, eaves, and any area within a few feet of an exterior wall typically get the self-adhering ice and water shield, since these are the spots most likely to see water backup during a heavy Pacific Northwest storm. Every seam should overlap correctly and get sealed, not just stapled and left exposed. If you're weighing whether a full tear-off and proper underlayment is worth it versus a step-by-step roof patch you can do yourself, our roofing services page breaks down when each approach makes sense for your home.
Step 3. Flash the valleys and install vents
Most roof leaks actually start at the flashing, not at the shingles themselves. Every spot where the roof plane changes direction, meets a wall, or gets interrupted by a pipe needs metal or rubber protection sized and shaped for that exact junction. This stage of the installation for roof process demands the most precision from your crew, and it's also the easiest to shortcut if nobody's watching closely.
Shingles shed water on a flat plane, but flashing is what stops water at every joint and corner.
Valley flashing done right
Valleys collect more water than any other part of your roof, since two slopes funnel runoff into a single channel. Your crew should install either a closed-cut valley, where shingles overlap the valley metal, or an open metal valley, where the metal stays exposed for maximum water flow. Open metal valleys handle heavy rain better and last longer, which matters in a region that sees plenty of it. Whichever method your contractor uses, the underlayment beneath the valley should already be doubled up with ice and water shield from the previous step, giving you two layers of protection before a single shingle touches that area.
Getting ventilation right the first time
Once valleys are flashed, your crew installs the ventilation components that keep your attic from cooking your shingles from underneath. Poor ventilation shortens shingle life dramatically and can void manufacturer warranties outright, so this isn't an optional add-on. A balanced system needs intake at the eaves and exhaust at the ridge, working together rather than one or the other:
Vent Type | Location | Purpose |
|---|---|---|
Ridge vent | Peak of the roof | Continuous exhaust for rising hot air |
Soffit vent | Underside of eaves | Intake for fresh air flow |
Box vent | Scattered on roof plane | Backup exhaust on complex rooflines |
Pipe boot | Around plumbing vents | Seals penetrations against leaks |
Boots around every plumbing stack and any exhaust pipe get sealed with a rubber gasket designed to flex with your home's settling and temperature swings over the years. Sizing your intake and exhaust vents correctly, based on your attic's square footage, keeps moisture from building up and rotting your deck from the inside, which defeats the whole purpose of the new roof you just paid for.
Step 4. Lay the starter course and shingles
With flashing and vents in place, your crew finally starts laying the material you actually see from the street. Starter shingles go down first along the eaves, a strip designed specifically to seal the first course from wind lift and give the visible shingles above something solid to bond against. Never let a crew cut regular shingles down and use them as a substitute starter course. That's a shortcut that leaves gaps between tabs exactly where wind-driven rain hits hardest, and it's one of the more common ways a discount installation for roof job fails within its first winter.
The starter course is the one row nobody notices until it fails, then everyone notices.
Getting the first courses square
Squaring off that first course matters more than people expect, since every row above it follows the same line. A crew working off a chalk line and consistent offset keeps your shingle pattern straight all the way to the ridge, while a sloppy start compounds into a visibly crooked roof by the time they're twenty rows up. Good crews snap chalk lines every few courses to check themselves against, not just at the eave.
Nailing patterns and exposure by shingle type
How your shingles get nailed matters as much as which shingles you picked. Manufacturer specs dictate nail placement, count, and exposure, and wind warranties get voided fast when a crew nails high or uses too few fasteners per shingle.
| Shingle Type | Nails Per Shingle | Exposure | Common Mistake | |---|---|---| | 3-tab asphalt | 4 | 5 inches | Nailing above the nail line | | Architectural/laminate | 4-6 | 5-5/8 inches | Under-nailing in high wind zones | | Impact-resistant | 6 | 5-5/8 inches | Using standard nails instead of ring-shank |
High-wind areas or steep pitches often call for six nails per shingle instead of four, plus a bead of roofing cement under each tab. Sealant strips on architectural shingles need direct sun and warmth to fully bond, so don't be surprised if your roof looks finished the day the crew leaves but doesn't reach full wind resistance for a few weeks. Roof installation steps like this one are exactly why manufacturer specs, not shortcuts, should drive every decision your crew makes on the ladder.
Step 5. Flash walls, cap the ridge, and seal the roof
The final stage of any installation for roof project happens where your roofline meets a wall, chimney, or dormer, and it's where a rushed crew leaves the most expensive leaks. Step flashing and counter flashing protect these transitions, and once they're in place, your crew moves to the ridge and the last details that turn a pile of shingles into a finished, weathertight roof.
The last few feet of flashing at a wall junction cause more callback leaks than the entire rest of the roof combined.
Step and counter flashing along walls
Wherever your roof meets a sidewall, chimney, or dormer, individual pieces of step flashing get woven in with each shingle course, one piece per course, never a single long strip bent to fit. Counter flashing then gets cut into the wall or siding above it, overlapping the step flashing so water runs down and over rather than behind it. Watch for these signs of a properly flashed wall junction:
Individual step flashing pieces, roughly 8x8 inches, tucked under each shingle course
Counter flashing embedded into siding or masonry, not just caulked on top of it
No exposed nail heads along the wall line
A clean reglet cut on masonry chimneys, sealed with high-grade sealant
Skipping counter flashing and relying on caulk alone is a common shortcut, since caulk degrades in a few seasons while metal flashing lasts as long as the roof.
Capping the ridge
Once the field shingles reach the peak, ridge cap shingles go on last, covering the ridge vent installed back in Step 3 while still allowing airflow underneath. These caps get a longer nail than field shingles, since they're driven through more layers, and they should overlap in the direction of prevailing wind so no exposed edge catches a gust and lifts. A crooked or gapped ridge line is one of the easiest defects to spot from the ground, so it's worth a look before your crew packs up.
Final seal and walkthrough
Before anyone leaves, every pipe boot, nail head, and flashing seam gets a final bead of roofing sealant, and a last magnetic sweep clears stray nails from your lawn and driveway. Your project manager should then walk the roof with you, or at least walk you through photos, pointing out the flashing details and confirming your locked-in price quote matched what actually went on your house.
What happens after your new roof is installed
Once the crew packs up, your job isn't quite done. Ask for copies of your manufacturer warranty registration and workmanship guarantee, and keep them somewhere you can find them in ten years. Final inspections with the city typically happen within a few days of completion, and your contractor should handle scheduling that without you having to chase them down. Photos from every stage, tear-off through ridge cap, should land in your inbox as documentation of what's now hidden under your shingles, and any follow-up work belongs with the crew whose roofing, siding, gutter, and skylight services you already trust.
Going through these roof installation steps should leave you confident you got what you paid for, not wondering what's hiding under the shingles. If you're weighing a full replacement or just want a second opinion before signing anything, get a free roof inspection and your 2026 Home Value Guide with a locked-in quote you can actually trust.
