How to Install a Tin Roof, Step by Step
Watching a crew snap chalk lines and run panels straight up a roof deck makes tin roof installation look simple. It isn't. One misaligned panel or a screw driven at the wrong angle can turn a 40-year roofing system into a leak source within two winters, and Kirkland's rain doesn't give you a second chance to catch a mistake early.
This guide walks through metal roof installation steps in the order a professional crew actually follows them, from tearing off old material and prepping the deck to fastening panels, sealing seams, and flashing every penetration. You'll see the tools and materials each stage requires, plus the small techniques, like proper overlap and screw torque, that separate a roof that lasts decades from one that fails at the first ice dam.
We put this together because so many Washington homeowners ask us the same question before calling for a quote: can I really do this myself? Whether you're tackling new construction metal roof installation or replacing worn shingles, you'll finish this article knowing exactly what the job demands, and whether it's a weekend project or one better left to a licensed crew.
What you need before installing a tin roof
Before you touch a single panel, get your gear, materials, and paperwork sorted. Most DIY roofing disasters start not with bad technique but with a missing tool halfway up a ladder or the wrong screw pattern bought in bulk. Metal roof installation rewards preparation more than any other exterior trade, because once panels start going down, you're committed to the layout you chose.
Tools and safety gear
You'll need more than a drill and a ladder. Pull together this list before you schedule a work weekend:
Cordless impact driver with a depth-adjustable screw gun attachment
Metal shears or a nibbler for cutting panels around vents and skylights
Chalk line and a laser level for keeping courses straight
Roofing harness, anchor points, and non-slip footwear rated for steep-slope work
Seam roller and rubber mallet for panel seating
Tin snips for trim and flashing adjustments
A roof is only as straight as the chalk lines you snap before the first screw goes in.
Materials to have on hand
Ordering the right quantities matters as much as ordering the right products. Underestimate panels or fasteners and you'll be waiting on a supplier mid-project while your deck sits exposed to weather.
Material | Typical Quantity | Notes |
|---|---|---|
Metal panels (steel or tin) | Roof area + 10% waste | Match panel profile to your existing roofline |
Synthetic underlayment | 1 roll per 400 sq ft | Ice-and-water shield at eaves and valleys |
Fasteners with neoprene washers | 2-3 per sq ft | Never reuse old fastener holes |
Ridge cap and trim | Linear footage of ridges/edges | Order matching color to panels |
Butyl sealant tape | 1 roll per 100 linear ft of seam | Critical for watertight laps |
Permits and code checks
Kirkland and most surrounding municipalities require a permit for new metal roof installation, especially on new construction or full tear-offs. Check with your local building department before ordering materials, since inspectors often want to see underlayment and flashing before panels go on. The International Code Council's residential code, adopted in most Washington jurisdictions, sets minimum fastening and underlayment standards you'll need to meet regardless of who pulls the permit.
Step 1. Prepare the roof deck and underlayment
Strip the old roofing down to bare decking before you plan anything else. Skipping this step to save a weekend is the fastest way to hide rot, soft spots, or old flashing failures under a brand-new metal roof. Roof deck preparation determines whether your panels sit flat or telegraph every dip and warp underneath them.
Inspect and repair the decking
Walk the entire deck on your knees, checking for spongy plywood, delaminated OSB, or fastener heads poking through. Replace any damaged sheathing now, not after underlayment goes down. Re-nail loose panels every 6 inches along the edges and 12 inches in the field, matching the original nailing pattern where possible.
A metal roof only performs as well as the deck hiding underneath it.
Roll out the underlayment
Start at the eaves and work upward, overlapping each course by at least 4 inches so water always sheds onto the layer below. Install ice-and-water shield along eaves, valleys, and around every penetration, extending it at least 24 inches past the interior wall line in Kirkland's climate. Staple or cap-nail the underlayment every 12 inches, then check that every seam lies flat before moving to panel layout. This stage of steel roof installation takes longer than most homeowners expect, but rushing it guarantees callbacks later.
Step 2. Measure and order your metal panels
Getting panel lengths wrong is the single most expensive mistake in metal roof installation how to projects, because custom-cut steel can't be shortened once it arrives. Measure twice, order once, and always round up to the nearest panel length your supplier stocks.
Take accurate roof measurements
Measure each roof plane from eave to ridge along the slope, not the flat horizontal distance, since pitch adds length you'll miss if you only measure the ground footprint. Record every valley, hip, and penetration separately, then note roof pitch with a level and protractor, since installation of metal roof panels depends on matching fastener spacing to slope.
Measure eave-to-ridge length on each plane
Record roof pitch (rise over run)
Note valley and hip lengths separately
Mark penetrations: vents, skylights, chimneys
Add 2-3 inches per panel for overhang
Order panels for the roof you actually measured, not the roof you assumed you had.
Choose panel profile and order lead time
Standing seam and corrugated profiles handle water differently, so match your choice to existing trim and local wind-load requirements before ordering. Most Washington suppliers need one to three weeks for custom lengths, and rushing this step for new construction metal roof installation often means mismatched runs later. Confirm color, gauge, and coating warranty match your quote sheet exactly before the truck leaves the yard.
Step 3. Install trim, flashing, and reference lines
Getting the trim and flashing right before a single panel goes down is what separates a watertight roof from one you'll be patching every spring. Metal roof installation steps at this stage focus on edges and penetrations, since those are the spots where water finds a way in if the layout underneath is sloppy.
Set eave and gable trim first
Start with drip edge along the eaves, fastening it every 12 inches with the leg tucked under the underlayment so runoff never touches bare fascia. Run gable trim next, overlapping each piece by at least 2 inches and sealing the laps with butyl tape before you snap a single reference line for panels.
Flash every penetration and valley
Install valley flashing before panels go up, centering a W-profile piece with a raised center rib so water from each side never crosses and backs up under the opposite panel. Wrap chimneys, skylights, and vent stacks with pre-formed boots or custom-bent flashing, sealing every edge with butyl tape rather than caulk alone, since caulk dries out years before the metal does.
A leak almost never starts in the panel field. It starts at a flashing seam someone rushed.
Snap your reference lines
Snap a chalk line parallel to the eave at your first panel's coverage width, then check it against a second line near the ridge to confirm the roof is square. This step of installation metal roof work catches framing irregularities before they turn into crooked courses across the whole slope.
Step 4. Set, fasten, and cap the panels
With trim and reference lines in place, you're finally ready for panels. This is where tin roof installation either comes together cleanly or unravels fast, because every panel you set influences alignment for the rest of the roof.
Set the first panel and check alignment
Align the first panel to your chalk line, letting it overhang the drip edge by the 1-2 inches you planned earlier. Snap it into the starter trim, check it's square with a level, and don't fasten it fully until you've confirmed the overhang matches on both eave and gable sides.
One crooked starter panel throws off every course that follows it.
Fasten with the right pattern and torque
Drive fasteners into the flat of the panel, never the ribs, spacing them 12 inches apart along the edges and every 24 inches in the field. Set your impact driver's clutch so the neoprene washer compresses without splitting, since overdriven screws are the top cause of early leaks in steel roof installation work.
Fasten flats, not ribs
Space screws per manufacturer spec
Check washer compression on every tenth screw
Overlap panels by one full rib
Cap the ridge and check every seam
Once all panels are set, install ridge cap over closure strips, fastening through both panel and cap for a sealed connection. Walk every seam afterward, checking for gaps, missed screws, or exposed underlayment before you call the job finished.
When to call in the pros
Some roofs simply aren't weekend projects. Steep pitches above 6/12, multiple valleys, or a deck with hidden rot push tin roof installation past what one impact driver and a Saturday can handle safely. If you've read through these steps and felt your stomach tighten at the flashing details or fastener torque, that instinct is worth trusting.
Getting from bare deck to a sealed, code-compliant roof takes practice most homeowners never get the chance to build. A single missed lap or overdriven screw can cost more in repairs than the labor would have in the first place, especially once Kirkland's rainy season starts testing every seam you cut corners on.
Skip the guesswork and the ladder trips. Request a free inspection and locked-in quote from Legacy Exteriors, and let a licensed crew handle the panels while you handle the coffee.
