Piss Poor ModBit Install in Austin

What this shows: Ponding water on a modified bitumen roof in Austin, still standing long after rain because of how it was installed and drained. It is on the site because it shows plainly what a poor low-slope install leads to.

Modified bitumen is a rolled low slope material installed in overlapping plies, and a bad install is usually obvious to anyone who knows what to look at. Laps are the whole system: they need the specified width, they need to run so water crosses them rather than into them, and the seam has to be fully bonded end to end rather than tacked. Ponding is the other tell. A low slope roof is supposed to move water to a drain or a scupper, and standing water days after rain means the slope or the drainage was never right, which no amount of material on top will fix. Fishmouths at the laps, unbonded edges and blisters are all symptoms of the same thing.

Published May 2026. Roofing Materials Guide covers this subject in full, and roofing in Austin is the local page for this work.