TPO, EPDM & modified bitumen
Flat & Low-Slope Roof Repair in Rosharon, TX
Water still standing on a flat roof forty-eight hours after the rain stopped is the warning sign, and it is the one everybody ignores until the ceiling tiles start coming down.
Flat roofs are not flat. Every low-slope roof is built with a fall, usually a quarter inch per foot, and its whole design assumes water leaves. Ponding is the symptom that something has stopped that happening: a blocked drain, a sagging deck, insulation that has taken on water and compressed, or a scupper that was never sized for a Gulf Coast downpour.
Standing water on a membrane accelerates every failure mode there is. It degrades the membrane by UV and by biological growth, it finds every seam, and on a deck already carrying more load than it was designed for it makes the low spot lower. Forty-eight hours is the industry benchmark and it is a good one.
The three membranes and where each belongs
TPO is a white single-ply thermoplastic and it is what goes on most new low-slope work around here. The seams are hot-air welded, which makes them as strong as the sheet, and the white surface keeps deck temperature down. That last point matters more in Rosharon than it does almost anywhere: a dark low-slope roof surface here passes 150 degrees on a July afternoon.
EPDM is black synthetic rubber, seamed with tape or adhesive. It is long-lived, forgiving to repair, and it absorbs heat rather than reflecting it, which makes it a better fit further north than it is here. Plenty of it exists on older Brazoria County buildings and it patches well.
Modified bitumen is the multi-ply torch-down or self-adhered asphalt system. Tough, good under foot traffic, and the sensible choice on a roof that people walk on for equipment access. It is also what most of the older commercial stock along FM 521 already has.
| System or repair | Installed price | Notes |
|---|---|---|
| TPO single-ply, per sq ft | $8.00 to $14.00 | White reflective, hot-air welded seams, 20 to 30 yr |
| EPDM rubber, per sq ft | $7.00 to $12.00 | Black, taped seams, easy to patch, runs hotter |
| Modified bitumen, per sq ft | $7.50 to $13.00 | Multi-ply, best where there is foot traffic |
| Silicone or acrylic roof coating, per sq ft | $2.50 to $5.50 | Restoration, not replacement. Needs a sound substrate |
| Seam or flashing repair | $450 to $1,600 | Where the failure is local and the field is sound |
| Ponding correction, tapered insulation | $4.00 to $9.00 per sq ft | Rebuilds the fall. The actual fix for standing water |
| Drain or scupper rebuild | $600 to $2,200 | Frequently the whole problem on an older roof |
Installed prices collected July 2026 for the Rosharon and north Brazoria County area. Low-slope pricing is per square foot rather than per square, which is how the commercial trade quotes it.
Is a roof coating a real repair or a delaying tactic?
A silicone coating is a real system when the substrate under it is sound and the failures are seams and small punctures rather than saturated insulation. Applied over a wet roof it seals the water in, and two years later the deck is worse and the coating has to come off before anything can be done properly. The honest test is a moisture survey before anybody quotes coating, and a contractor who skips that step and offers a price over the phone is selling you time, not a roof.
Where flat roofs turn up in Rosharon
Commercial and light industrial along the SH-288 corridor and FM 521, the strip retail around Iowa Colony and Manvel, churches, and the low-slope sections that show up on residential additions, patio covers and porch roofs. That last category causes the most residential trouble, because a patio cover tied into a pitched roof is a detail that gets built badly and then leaks into the main house.
Commercial structures in Brazoria County have the same windstorm requirement
TDI's building standards apply to commercial structures insured for wind and hail through TWIA, not just to houses. The maximum commercial limit is $4,424,000 as of January 2026 and the per-occurrence deductible on commercial risks starts at 1 percent per item. Worth confirming before a low-slope re-cover gets value-engineered. See how certification works here and the commercial roofing page.
How long should a flat roof last on the Gulf Coast?
Twenty to thirty years for TPO, twenty to thirty for EPDM, fifteen to twenty-five for modified bitumen, assuming the drains stay clear and nobody drops an air conditioning unit through it. Drainage maintenance is the single highest-return thing an owner does: a clear drain costs nothing and a blocked one is how a roof ages ten years in two.
Where we do this work
Low-slope work across the commercial corridors and on residential additions throughout the service area.
Flat & Low-Slope in Iowa Colony, Arcola flat & low-slope, Flat & Low-Slope for Manvel properties, Flat & Low-Slope in Fresno, Sienna flat & low-slope, Flat & Low-Slope for Brookside Village properties, Flat & Low-Slope in Pearland, Alvin flat & low-slope, Flat & Low-Slope for Missouri City properties, Flat & Low-Slope in Damon, Angleton flat & low-slope, Flat & Low-Slope for Danbury properties, Flat & Low-Slope in Liverpool.
Related: Commercial & Industrial Roofing · Roof Maintenance & Coatings · Roof Repair & Leak Repair · Emergency Roof Repair & Tarping
Water sitting on your flat roof two days after the rain?
That is fixable, and the fix is drainage rather than another layer of coating.
Call (281) 845-8668- A roofer answers, not an answering service
- Written line-item scope before any work starts
- We never touch your deductible, and Texas law is why
Have a doubt
Flat roof questions
How much does flat roof replacement cost in Rosharon?
TPO costs $8 to $14 per square foot installed in Rosharon, EPDM is $7 to $12 and modified bitumen is $7.50 to $13. On a 2,000 square foot low-slope roof that is roughly $14,000 to $28,000 depending on system and insulation.
Why does my flat roof pond water?
Ponding means water is not leaving, and the usual causes are a blocked drain or scupper, a deck that has sagged, or insulation that has taken on water and compressed into a low spot. Water still standing after forty-eight hours is the benchmark for a problem worth addressing rather than watching.
Can you coat my flat roof instead of replacing it?
Sometimes, and only after a moisture survey. Coating a sound roof with local seam failures is a genuine restoration. Coating a roof with saturated insulation seals the water in and makes the eventual replacement more expensive. Anyone quoting a coating over the phone has not done the test that decides it.
Is TPO better than EPDM in Texas?
Generally yes, on heat alone. TPO's white surface reflects solar radiation where EPDM's black surface absorbs it, and deck temperature on a Rosharon roof in July is the governing condition. EPDM has real strengths in ease of repair and longevity, which is why it is still worth specifying on some buildings, particularly ones with heavy penetration counts.