Commercial Roofing
San Marcos Commercial Flat Roof
4,200 sq ft TPO membrane installation on a San Marcos auto parts supplier. Three years of patch failures fixed with a properly engineered drainage solution and 60-mil TPO system.
The Story
This San Marcos auto parts supplier had been fighting the same roof for three years. A previous contractor had patched it four separate times. The patches held temporarily, then leaked again. The root cause was never addressed: a persistent ponding water problem in one corner of the building was accelerating the breakdown of the existing built-up roof system.
Red Roan started with a full deck assessment. We found what we expected in the problem corner - 180 sq ft of rotten decking that had been absorbing water for years. That came out first. Once the deck was clean, we understood exactly what the drainage issue was: the existing roof had no slope correction in that area, so water had nowhere to go after rain.
The fix was tapered polyisocyanurate insulation in the low corner, designed to redirect drainage toward the roof drain rather than let it sit. With the drainage solved, we installed a 60-mil TPO membrane, mechanically fastened across the full 4,200 sq ft. All six HVAC penetrations got new flashings - every one of them was a future leak in the old system.
Four days total including the deck repair. The building owner told us this is "the last roof we'll have to deal with for 20 years." Based on the system we put in, he is right.
Project Specs
- 4,200 sq ft commercial building
- 60-mil TPO membrane, mechanically fastened
- Tapered insulation - low corner drainage correction
- 180 sq ft rotten deck replaced
- 6 HVAC penetrations resealed and flashed
- 4-day install including deck repair
- San Marcos, TX - December 2024
- 20-year expected service life
Outcome
Chronic ponding eliminated with tapered insulation. Rotten deck replaced. All penetrations resealed. Four-year patch cycle ended. Building owner expects no further roof expenditure for 20 years.
Why the Patches Kept Failing
A pattern we see often on commercial flat roofs. Symptoms get treated, the root cause stays.
Standing water
Ponding degrades membrane adhesion and accelerates delamination in built-up systems.
Rotten decking
Wet deck means patches have no solid substrate. They fail fast and the water follows the same path.
Unfixed penetrations
HVAC penetrations are the most common leak points on commercial flat roofs and are routinely skipped in patch jobs.
Commercial Flat Roof Problems?
If you have had the same area patched more than twice, you need an assessment not another patch. We will tell you exactly what is happening and what fixing it properly costs.