Flat Roof Repair in Lewisville, TX

If you need flat roof repair in Lewisville, TX, there is a reasonable chance the actual problem is not where the water is coming through. Most low-slope roof failures we open up are drainage problems rather than material problems, and patching the wet spot without fixing why water sat there in the first place simply moves the failure a few feet along.

What Counts as a Flat Roof

Almost nothing is genuinely flat. What people call a flat roof is a low-slope roof, and the distinction that matters is set by code. The International Residential Code establishes a minimum slope of two units vertical in twelve units horizontal for asphalt shingles, and requires doubled underlayment where the slope is between two and four in twelve.

Below two in twelve, shingles will not shed water reliably regardless of how well they are installed, because water moves too slowly and wind drives it back up under the courses. That is why a low-slope section needs a membrane rather than shingles, and why one of the most common problems we find on residential additions is a porch, dormer or room extension shingled at a slope that never should have been.

• Residential low-slope sections. Porch roofs, carports, dormers, sunrooms and rear additions, very common on 1970s and 1980s homes in Carrollton and Original Town Lewisville.
• Full low-slope residential roofs. Mid-century and modern designs, occasionally found in Denton's older neighborhoods.
• Commercial and light industrial decks. The dominant roof type across the Lewisville and Coppell distribution corridor.
• Roof-mounted equipment platforms. Areas around HVAC curbs which are effectively flat regardless of the surrounding slope.

Ponding Water: The Root Cause of Most Flat Roof Failure

Water that is still sitting on a roof 48 hours after rain has stopped is ponding, and it is the single most destructive condition a low-slope roof experiences.

It causes damage in several ways at once. Constant saturation breaks down membrane and adhesive chemistry far faster than intermittent wetting. Standing water carries substantial weight, and a large ponded area represents a real dead load on a deck that may not have been designed for it, which deflects the deck further and deepens the pond. Debris and organic growth collect in the water and hold it. And in a North Texas summer, water sitting in direct sun accelerates the thermal degradation of everything it touches.

Ponding almost always has one of four causes: a blocked or undersized drain, a crushed or saturated area of insulation creating a low spot, deck deflection from age or load, or a roof that was built without enough slope to begin with. Fixing the membrane without addressing which of those four it is guarantees the repair fails.

The Repairs We Perform Most on Low-Slope Roofs

Flat roof repair is detail work, and the details are consistent across systems.

• Seam repair. On TPO, re-welding seams that were cold-welded or contaminated at installation. On modified bitumen, re-adhering laps that have lifted or fishmouthed.
• Blister repair. Cutting out the blistered area, drying or replacing wet insulation beneath, and patching in new membrane welded or adhered to sound material.
• Pitch pan refilling and rebuilding. The sealant in a pitch pan shrinks and cracks over time. Refilling is routine maintenance; rebuilding is needed once water has been getting past it for a while.
• Drain and scupper repair. Clearing, resealing the drain flange to the membrane, and correcting undersized or badly positioned outlets.
• Parapet and curb flashing. Wall terminations and equipment curbs move differently from the roof field and pull apart at the transition.
• Tapered insulation correction. Building slope into a low area so water actually reaches a drain instead of sitting.
• Walkway pad installation. Protecting the paths HVAC technicians take to rooftop units, which is cheap compared with repairing the abrasion damage they cause.

Flat Roofs in Lewisville: Residential and Commercial

On the residential side, the low-slope problems we see most are on 1970s and 1980s additions across Carrollton, Original Town Lewisville and older Denton neighborhoods, where a porch or rear extension was shingled at a slope well below the two-in-twelve code minimum. Those roofs leak from the day they are built and no amount of shingle work fixes them. The correct repair is to convert the section to a membrane or a mechanically seamed metal system.

On the commercial side, the Lewisville and Coppell corridor is dense with distribution and light industrial buildings carrying large single-ply roofs, most of them with substantial rooftop HVAC loads. There, the recurring issues are drainage, foot traffic damage along service routes, and pitch pans nobody has refilled since the building was handed over. Denton County hail adds membrane puncture to that list on a fairly regular cycle.