Flat Roof Leaks, Ponding Water And Energy Loss: How A Commercial Roofer In Frisco Fixes Them

Frisco's commercial stock is heavy on low-slope roofs: retail strips, medical and office buildings, warehouses and light industrial. A low-slope roof is not flat, it just does not have enough pitch to shed water by gravity alone, which means everything depends on drainage and on the details around every penetration.

Problem 1: Leaks, And Where They Actually Start

Field membrane rarely fails first. In our experience on Frisco buildings the leak is nearly always at one of five places:

• Seams. Heat-welded TPO and PVC seams are strong when welded correctly and are the weakest point when they are not. A probe test along a seam finds this in minutes.
• Penetrations. HVAC curbs, vents, conduit, gas lines. Every one is a hole in the roof that depends on a boot or a flashing detail staying sealed.
• Perimeter and coping. Wind uplift works on the edges hardest, and a lifted edge lets water in behind the membrane where you cannot see it.
• Drains. Clamping rings loosen, strainers vanish, and the drain sump becomes the leak.
• Old mechanical work. A unit swapped out by someone who is not a roofer, with the penetration sealed by whoever happened to be there.

Because water travels along the deck before it appears, the wet ceiling tile is almost never under the breach. That is why a real assessment means infrared or moisture scanning across the field rather than patching where the drip is.

Problem 2: Ponding Water

Water standing more than 48 hours after rain is ponding, and it is a drainage failure rather than a membrane failure. It matters for three reasons: standing water accelerates membrane breakdown and seam stress, it is heavy at roughly five pounds per square foot per inch of depth, and it collects debris that blocks the drain that was supposed to clear it.

The fixes, in order of how often they are the right one:

1. Clear and repair the drainage. Blocked drains and scuppers explain a surprising share of ponding. Cheapest thing on the list.
2. Add drains or scuppers where the roof has low areas the original design did not serve.
3. Tapered insulation to build positive slope into the low area. This is the durable fix where the deck itself is flat or has deflected.
4. Structural assessment if the deck is deflecting under load, because at that point the roof is a symptom.

Problem 3: Energy Loss

A dark, aged low-slope roof in a Frisco summer runs extremely hot, and that heat goes into the building. Two levers change it. A reflective membrane surface, which the Department of Energy notes lowers roof surface temperature substantially compared with a dark one. And insulation, because most older low-slope assemblies here are under-insulated by current standards.

The important detail is that wet insulation is not insulation. If a moisture scan shows saturated board under the membrane, you are paying to cool a building through a wet sponge, and no amount of surface reflectivity fixes it. Replacing the wet sections is usually the measure that pays.

Repair, Restore Or Replace

Restoration coatings have a real place and are oversold. They renew a surface. They do not dry out wet insulation and they do not fix slope. Anyone proposing a coating without a moisture scan first is guessing.

What To Ask For

A commercial assessment worth paying attention to includes a moisture survey, photographs of every penetration and seam tested, a drainage assessment with the ponding areas marked on a roof plan, and options priced separately rather than one number. Then a maintenance schedule, because on a low-slope roof twice-yearly drain clearing and seam checks are what keep the big number away.

Sources: U.S. Department of Energy, Cool Roofs · NRCA Roofing Guidelines