Replacement and new roofs
Flat and low-slope roofing for Dallas homes
Shingles need slope. The flat roof on a modern home, the porch roof under a second-story window, and the low addition off the back all need a membrane, and they leak when someone shingled them anyway.
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Quick answer
Flat and low-slope roofing on Dallas homes uses a continuous membrane, usually white TPO or modified bitumen, instead of shingles on any section with too little slope for shingles to shed water. We install it on modern flat-roof homes, porch and patio roofs, and low additions, with tapered insulation or crickets to stop ponding and careful tie-ins where the low roof meets a shingled one.
Warning signs
Signs a low-slope section is failing
Water standing after rain
The slope is wrong or has sagged.
Leaks where porch meets house
Tie-in was caulked, not flashed.
Shingles lifting on a shallow pitch
Below the minimum slope.
Blisters in the membrane
Moisture trapped underneath.
Stains on the porch ceiling
Water through the low section.
Moss in low spots
Chronic dampness.
Split seams at the edge
Old membrane shrinking.
The job
Why low-slope sections leak on so many houses
Asphalt shingles shed water by overlapping; on a very shallow slope, wind-driven rain pushes water uphill under the laps. The building code sets a minimum slope for shingles and requires extra underlayment on the shallow end of the range, but many porch and addition roofs were shingled below it anyway, and they leak at the first hard rain.
Residential flat roofs are small, full of details and sit next to walls and windows. That makes them a different job from a warehouse roof, even when the membrane is the same.
Updated September 2026
Budget
What decides the cost of a low-slope roof
Residential flat roofs are small but detailed; there is no published Dallas range that fits them. These factors set the number.
- Area
Priced per square, usually a small area.
- Membrane choice
TPO or modified bitumen.
- Tapered insulation
Added where water ponds.
- Wall tie-ins
Siding or stucco opened for counterflashing.
- Tie-in to shingles
Where the low roof meets the main roof.
- Drainage
Scuppers, gutters and downspouts.
- Decking
Soft sheathing replaced before membrane.
Your options
TPO or modified bitumen on a house
Both work on residential flat roofs; they suit different uses.
| Compare | TPO | Modified bitumen |
|---|---|---|
| Surface | White, reflective | Granule cap, many colors |
| Foot traffic | Occasional | Regular, including roof decks |
| Install | Heat-welded seams, no flame | Self-adhered or torch-down |
TPO membrane
White TPO from Carlisle SynTec, Firestone or GAF is the usual choice for a residential flat roof in Dallas: it reflects the summer sun, the seams are heat welded into one sheet, and it is light enough for any existing framing. We install it fully adhered over new insulation board, which keeps it quiet in wind and gives a firm surface for occasional foot traffic. Walls are flashed with membrane turned up behind the siding or stucco, and every edge gets metal drip edge or a coping cap.
Modified bitumen
Modified bitumen is a multi-ply asphalt roof with a granule cap sheet, tough under foot traffic and forgiving on awkward details. On homes where a flat roof doubles as a deck or gets walked for maintenance, or where the neighbors' roofs are all dark, we often recommend it. Self-adhered mod bit avoids open flames next to wood siding, which matters on a house. The cap sheet color can be matched close to surrounding shingles. Seams lap downhill on every ply.
Ponding and tapered insulation
A residential flat roof that holds water after rain is either framed dead flat or has sagged. Rather than patching the membrane in the puddle, we fix the slope: tapered insulation boards build in a quarter inch per foot toward the drain or edge, and crickets divert water around chimneys and wall corners. Where the roof drains through a scupper to a gutter, the scupper is resized and reflashed, because an undersized scupper is often why the water sits there.
Patio and porch low-slope sections
The porch roof or patio cover tied into a house is the most common low-slope leak we see. Often it was shingled below the minimum slope, or the joint where it meets the house wall was simply caulked. We strip it, install membrane over the whole low section, run it up under the house siding with proper counterflashing, and tie it into the shingled roof above so water crossing from one to the other always laps downhill. The ceiling below is checked for wet framing first.
Roofing in Dallas
What we see on Dallas roofs
The 2021 International Residential Code, as Dallas amends it, is what sets the minimum slope for asphalt shingles and the extra underlayment required near it. It is also why a low porch or addition roof that someone shingled too flat tends to fail an inspection on a later re-roof. When we replace one of those roofs we build it to the code for its actual slope, which usually means membrane on the flat section and shingles only where the pitch allows them.
What happens after you call
How a low-slope roof job runs
Measure the slope
Confirm whether shingles are even allowed there.
Find the water path
Where it ponds, drains and meets walls.
Scope and membrane
TPO or mod bit, tapered design, tie-ins.
Strip
Old shingles or membrane removed; deck checked.
Insulation and slope
Tapered boards and crickets set.
Membrane and flashing
Installed, welded or rolled, walls counterflashed.
Water test
Hose test at every tie-in.
Brands we install and service
Questions we get
Flat and low-slope roof questions
Only if the slope meets the code minimum; below it, a membrane is required.
TPO for reflectivity; mod bit where the roof is walked.
It was framed too flat or has sagged; tapered insulation fixes it.
On most flat roofs it is not visible from the street.
Yes, with the membrane lapping under the shingles above.
Fully adhered membrane over insulation is quiet.
Occasionally; mod bit handles regular traffic better.
Yes, whole roofs as well as sections.
Same category
Related replacement & new roofs work
Porch roof leaking where it meets the house?
It is usually a slope or tie-in problem, and it is fixed with membrane, not more caulk.