We install PVC, TPO, torchdown, Duradek and standing seam metal, and your pitch tells us which ones fit.
Flat roofs run a median of $12.86 per sq ft, plus tax, based on 569 average RoofSmart jobs in the last 12 months, with outliers left out.
If you're seeing leaks, dealing with pooling water, or noticing signs of water damage on your roof, it’s easy to feel overwhelmed.
Seattle’s rain doesn’t just test your patience; it tests your roof’s resilience.
The right material lasts longer and needs fewer repairs.
Our team doesn’t just install these materials; we evaluate your specific needs and guide you to the best choice for your home or business.
When you own a flat or low-slope roof, every rainstorm can bring anxiety.
Will the roof hold up? Are small leaks turning into big problems?
The last thing you need is to worry about water creeping into your walls and damaging your roof.
Many roofing companies promise quick fixes, but quick isn’t always right.
You deserve a roof built for Seattle’s unique climate that gives you confidence instead of concern.
At RoofSmart, we understand your concerns. Our mission is to make your roof the last thing you worry about.
We’re Meticulous Roofing Nerds, meaning we combine our deep passion for roofing with a laser focus on every detail.
We study materials, master techniques, and execute every project with precision.
We know what keeps flat and low-slope roofs performing at their best, from material selection to installation methods.
Our expertise allows us to customize these flat roof materials to meet your roof’s needs and keep water where it belongs: outside.
Roof pitch is rise over run: a 2:12 roof climbs 2 inches for every 12 inches across.
The National Roofing Contractors Association (NRCA) defines low slope as 3:12 or less, and that includes flat roofs.
Even a "flat" roof should fall gently toward its drains.
(NRCA, Professional Roofing, April 2013)
Not sure of your pitch? Our post on what roof pitch is and why it matters shows how it's measured.
| Roof type | Code minimum slope | Code section |
|---|---|---|
| Asphalt shingles | 2:12 (we require 3:12), with a double layer of underlayment from 2:12 up to 4:12 | 2021 IRC R905.2.2; R905.1.1 and Table R905.1.1(2) |
| Standing seam metal | 1/4:12 | 2021 IRC R905.10.2 |
| Lapped metal panels with applied sealant | 1/2:12 | 2021 IRC R905.10.2 |
| Lapped metal panels without sealant | 3:12 | 2021 IRC R905.10.2 |
| Thermoset and thermoplastic single-ply membranes | 1/4:12 | 2021 IRC R905.12.1 and R905.13.1 |
| Modified bitumen, including torchdown | 1/4:12 | 2021 IRC R905.11.1 |
| Built-up roofs | 1/4:12 (coal-tar built-up: 1/8:12) | 2021 IRC R905.9.1 |
Washington enforces the 2021 IRC with state amendments (WAC 51-51), and those amendments don't change these slope values.
The 2024 edition is scheduled to take effect May 3, 2027.
These are the floor, not the target. When a manufacturer's instructions call for more slope, the manufacturer's minimum wins.
Source for the table: 2021 Seattle Residential Code chapter 9, which reproduces the 2021 IRC.
Code is one thing; what lasts in Seattle rain is another. Here's what we put on each pitch:
Shingles need at least 3:12. Code allows 2:12 in most areas, but that's too low for us.
Jim explains why in the minimum slope for shingles, and our post on metal on a low-slope roof covers standing seam.
If you want shingles on a roof under 3:12, we're not the right fit, because 3:12 is our minimum even where code allows 2:12.
Water runs off a low slope slowly, and on a flat roof it can sit.
Ponding water wears a membrane down and feeds leaks, as we explain in does a Seattle flat roof really need a taper system.
Shingles at too low a pitch let water seep back under the laps during long wet spells. That's why we hold shingles to 3:12.
There are three ways: tapered insulation boards, lightweight insulating concrete or framing the slope in wood.
Framing usually costs the least, then tapered insulation, and insulating concrete costs the most.
Which one fits depends on your structure and drains. We compare all three in how to add slope to a flat roof.
PVC is one of the four membranes we install.
Read which PVC roofing brand is best for Seattle, then see what the warranty covers on a residential PVC roof or a commercial PVC roof.
See finished flat and low-slope jobs in our flat and low-sloped roofing gallery.
Want to know what fits your pitch? Book a free SmartMatch Needs Analysis with a member of our sales team.
Our free instant estimate tool is designed to provide you with a fast, accurate, and no-obligation quote tailored to your specific roofing needs.
Enter a few details, like your roof’s size and condition. We’ll build a personalized estimate from current industry standards and material costs.
Our roofing process is all about YOU. You tell us what kind of roof you want and then we make it happen.
Tell us about your flat or low-slope roof and we'll set up your free SmartMatch Needs Analysis.
Leaking right now? See roof repair or call (206) 487-4877.
Reach out to us today to schedule a free SmartMatch Needs Analysis and meet with your very own meticulous roofing nerd.
Now it’s time for your roof work to begin!
The best part? You got to choose everything based on your needs, your preferences, and your budget.
Congrats! You now have the roof of your dreams.
Most importantly, your roof is now working at its best.
