Flat and low-slope roofing in Conroe — patio covers, porches, additions and small commercial
The flat roof over the patio, the low-slope porch on the 1970s ranch house, the shop office addition — the parts of a Conroe roof that leak first, done in TPO or modified bitumen that handles 100-degree sun and two-inch downpours.
Almost every flat roof we see in Conroe is a piece of a bigger roof: the patio cover somebody added in 2005 with a roll of granulated roofing, the low-slope porch across the front of a River Plantation ranch house, the flat section over a garage conversion, the office bump-out on a shop off Highway 105. They leak because they were built with steep-slope thinking — shingles on a two-in-twelve pitch, no proper tie-in where they meet the wall, a drain at the high point — and because the sun on a flat roof here is brutal.
We replace those with the two materials that actually work on low slopes in Texas: TPO, a white heat-welded single-ply membrane that reflects the sun, stays cool and has no seams that can fail except the ones welded in the factory and in the field; and modified bitumen, a two-layer torch-down or self-adhered asphalt system that's tough, granule-surfaced and the right choice where a roof gets foot traffic or where it has to tie into a shingle roof cleanly. Either way, we fix the pitch with tapered insulation where water is ponding, rebuild the wall flashing properly, and put drains and scuppers where the water actually goes.
What's included
TPO single-ply
45- or 60-mil white TPO, heat-welded seams, over cover board or tapered insulation; cool-roof rated.
Modified bitumen
Two-ply SBS modified bitumen, self-adhered or torch-applied, granule-surfaced — for porches, patio covers and tie-ins.
Tapered insulation
Polyiso tapered to move ponding water to the drains, adding R-value over the space below.
Wall & transition flashing
Proper termination bars, counter-flashing and shingle-to-membrane tie-ins — where most flat-roof leaks live.
Drains & scuppers
Overflow scuppers, new drains and gutters sized for two-inch-an-hour rain.
Repairs & re-covers
Patches, seam re-welds and full re-covers over sound existing membranes where the deck is dry.
Flat roof cost in Conroe, TX
| Job | Typical price | Notes |
|---|---|---|
| TPO patio cover or porch roof (up to 400 sq ft) | $3,200 – $6,500 | Membrane, flashing, drip edge |
| Modified bitumen porch or addition roof (up to 400 sq ft) | $2,800 – $5,800 | Two-ply, granulated |
| TPO re-roof, larger flat section or small commercial | $7 – $12 per sq ft | Includes tapered insulation where needed |
| Flat-to-pitched tie-in rebuild | $700 – $2,200 | Where the flat meets the shingle roof |
| Flat roof repair — seam, flashing or patch | $350 – $1,200 | Same-week |
| Ponding correction with tapered insulation | $3 – $6 per sq ft | Fixes the standing water, not just the leak |
These are 2026 Montgomery County ranges so you can budget. Your written price is itemized — tear-off, decking allowance, underlayment, shingles or panels, flashing, ventilation, haul-off — and good for 30 days.
Recent work
Questions we get about flat & low-slope roofs
Can you put shingles on my flat porch roof?
Not if it's under a 2:12 pitch — the manufacturers don't warrant it and it will leak. Between 2:12 and 4:12, shingles can go over a full ice-and-water underlayment. Below that, it's a membrane roof: TPO or modified bitumen.
TPO or modified bitumen?
TPO for anything that bakes in full sun and where you want the coolest roof — patio covers, shop offices, additions. Modified bitumen where the roof gets walked on, where it ties into shingles, or where you want a granulated look from a second-story window.
Water stands on my flat roof after rain. Is that bad?
Ponding that's still there 48 hours after a rain shortens any membrane's life and finds every weak seam. Tapered insulation fixes the slope so the water reaches the drain; adding a scupper fixes the drain that's in the wrong place.
How long does a flat roof last in Texas?
TPO 20 to 25 years, modified bitumen 15 to 20, both assuming the water drains. A rolled-roofing patio cover put on with a torch and good intentions: 5 to 8.
Can you repair it instead of replacing it?
Often. A seam re-weld, a new flashing at the wall or a patch over a puncture is a few hundred dollars. When the membrane is chalking, cracked and patched in five places, replacement is the honest answer.
Do you do flat roofs on commercial buildings?
Yes — strip centers, shops, churches and small warehouses. See our commercial roofing page.