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Flat & Low-Slope Roofing (TPO / PVC)
Heat-welded membrane systems for flat roofs, dormers, and additions.
- Lifespan
- 20 – 30 years
- Range
- $8 – $14 per sq ft
- Warranty
- Manufacturer + 5-yr GripGo
What it is & how it works
Flat & Low-Slope Roofing (TPO / PVC) in plain English
For flat roofs, dormers, modern additions, and low-slope sections, we install single-ply TPO and PVC membrane systems. Every seam is heat-welded into one continuous waterproof surface — no adhesives to fail, no seams to leak.
TPO (thermoplastic polyolefin) and PVC membranes are mechanically fastened or fully adhered over rigid insulation, then hot-air welded at every seam to create one monolithic waterproof layer. The bright white surface reflects up to 85% of solar heat, cutting cooling costs on flat roofs that would otherwise bake in the summer sun. We install .060 gauge (heavy commercial grade) membrane as standard, with tapered insulation to eliminate ponding water — the #1 killer of flat roofs.
Understanding your options
Tiers, styles & what's included
Tap any tier to see exactly what's in it, what it costs relative to the others, and who it fits best.
Option 1TPO (Thermoplastic Polyolefin)
TPO (Thermoplastic Polyolefin)
The most common commercial-grade flat roof membrane. Bright white, heat-welded, and cost-effective.
- .060 gauge (60 mil) standard, .080 upgrade available
- Reflects up to 85% of solar heat (ENERGY STAR)
- 20 – 25 year manufacturer warranty
- Best value in the flat-roof category
Option 2PVC (Polyvinyl Chloride)
PVC (Polyvinyl Chloride)
Premium membrane — chemical, fire, and grease resistant. Ideal for restaurant kitchens, urban roofs, and rooftop decks.
- Resistant to grease, oils, and rooftop chemicals
- Highest fire resistance in single-ply
- 25 – 30 year warranty
- Best for rooftop decks with planters or hot tubs
Option 3EPDM (Rubber) Roofing
EPDM (Rubber) Roofing
Black synthetic rubber membrane. Extremely durable and flexible — the traditional flat-roof choice.
- 40+ year lifespan
- Handles extreme temperature swings
- Best for shaded flat roofs (dark color)
- Great for garages, sheds, and back-of-house additions
Option 4Modified Bitumen (Torch-Down)
Modified Bitumen (Torch-Down)
Asphalt-based rolled membrane, torch-applied or self-adhered. A proven, workhorse flat-roof system.
- Two or three plies for redundant waterproofing
- Granulated cap sheet in matched colors
- 20 – 25 year lifespan
- Great for tight, complex flat sections
Option 5Rooftop Deck-Ready Systems
Rooftop Deck-Ready Systems
Membrane roof with pedestal-set pavers on top — a waterproof roof AND a usable outdoor space.
- Fully accessible for inspection under pavers
- PVC membrane rated for foot traffic
- Integrated planter and drain flashings
- Ideal for townhomes and view lots
Option 6System Details (Every GripGo Flat Roof)
System Details (Every GripGo Flat Roof)
Ponding water kills flat roofs. Our build eliminates it.
- Tapered polyiso insulation (R-25+ typical)
- 1/4" per foot minimum slope engineered into every roof
- Heat-welded seams tested with a probe
- Coping cap and edge metal color-matched
- Every penetration flashed with pre-fab pipe boots
- Annual inspection option to keep warranty active
The system
Anatomy of a low-slope roof
A roof is a stack of layers — each one has a job. Here's what goes into every one we build, in plain English.
- TPO / PVC / EPDM membraneThe waterproof top sheet — heat-welded or seam-taped
- Cover boardProtects the membrane from foot traffic and hail
- Rigid insulation (ISO)R-value + slopes water toward drains
- Vapor barrier (as needed)Blocks interior moisture from reaching insulation
- Roof deckStructural surface (plywood, metal, or concrete)
The honest take
Advantages & things to consider
Advantages
- Fully welded seams — truly watertight
- Reflective white surface cuts cooling costs
- 20-30 year manufacturer warranties
- Great for adding a rooftop deck later
Things to consider
- Requires specialized welding equipment and training
- Punctures need immediate repair (we offer annual inspections)
Is this right for your home?
Quick fit check
What GripGo inspects
Free on-site inspection checklist
Every quote starts with a real inspection — not a driveway guess. Here's what we look at before we write a single number down.
Membrane seams and heat-welded laps
Perimeter and edge flashing
Curbs, penetrations, and pipe boots
Drains, scuppers, and overflow paths
Ponding areas and slope-to-drain
Insulation moisture (infrared where needed)
Common questions
What Seattle homeowners ask us about flat & low-slope roofing (tpo / pvc)
Are flat roofs really flat?+
No — every flat roof needs a minimum 1/4" per foot slope to shed water. When we install a new flat roof we build the slope into tapered insulation, so even 'perfectly level' framing gets proper drainage.
TPO vs PVC — which do I want?+
TPO is the best value and handles 90% of Seattle flat roofs perfectly. Upgrade to PVC if you have a restaurant kitchen, rooftop deck with planters, or chemical exposure (HVAC oils, coolant lines). Both are heat-welded and warrantied 20+ years.
How do I know if my flat roof is failing?+
Watch for: ponding water 48+ hours after rain, seams lifting or bubbling, brittle or cracked edges, or interior stains along ceiling perimeters. Annual inspections catch all of these before they become leaks — we offer them for $195/year.
Can you install a rooftop deck on my flat roof?+
Yes. We install PVC membrane rated for foot traffic, then set pedestal pavers on top. The membrane is fully accessible for inspection by lifting a paver — no need to demo the deck if there's ever an issue.
Related services
Also worth a look
Asphalt Shingle Roofing
The Pacific Northwest workhorse — affordable, proven, 30+ year lifespan.
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Composite / Synthetic Roofing
The look of slate or cedar — engineered to outlast both, with 50-year warranties.
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Metal Roofing
Standing seam and metal shingle — 40 to 70+ year lifespan, energy-efficient.
Learn moreReady when you are
Free inspection, honest recommendation, no pressure. That's how we've done it since day one.