Staff Answer
May 12, 2026 - 10:06 AM
For an 18 ft x 7 ft roof, you’ve got 126 square feet to cover, most TPO adhesives cover roughly:
- 60–70 sq ft per gallon per side for bonding adhesive (when applied to both surfaces)
- Or about 120–140 sq ft per gallon for some single-side water-based adhesives
So the exact amount depends on the adhesive type, but as a safe estimate:
- 2 gallons is usually enough for a standard install
- 3 gallons gives you comfortable extra coverage and recommended if this is your first time installing TPO
A few tips for getting the TPO laid down smooth without bubbles or wrinkles:
Best way to install it
- Roll the TPO out on the roof first and let it relax in the sun for 20–30 minutes if possible.
- Fold one half back.
- Apply adhesive evenly.
- Let the adhesive flash off until tacky (not wet).
- Slowly roll the membrane back into place while smoothing as you go.
If you don’t have a membrane roller
You can still get good results using:
- A push broom
- A heavy shop broom
- A laminate flooring roller
- A section of PVC pipe wrapped in a towel
- Even clean kneepads + hand pressure working from center outward
The key is:
- Start in the middle
- Push air outward toward the edges
- Work slowly in small sections
To avoid bubbles/crinkles
- Don’t install when the membrane is cold
- Don’t stretch the TPO tight
- Let the glue tack before laying membrane down
- Keep tension even while unrolling
- Smooth immediately as you lay it
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