Flat and Low-Slope Roofing in St. Louis

Should the tear-off expose rot in the decking, we stop and show you before replacing a single board. No surprise line items appearing on the final invoice.

First the vocabulary, because it changes the approach: nothing is truly flat. Low-slope means under roughly three-in-twelve, and below that pitch water does not shed fast enough for shingles to work. Shingles rely on gravity and overlap, so put them on a two-in-twelve porch roof and wind-driven rain will push water up under the courses. A good share of the low-slope work we do in this metro is correcting exactly that: a porch, an addition or a dormer tie-in that got shingled because the rest of the house was.

Ponding is the core problem. Water standing beyond about two days after rain means either insufficient slope or blocked drainage, and standing water will find any marginal seam, magnify UV damage and add real structural load. The fix is sometimes as simple as clearing drains and scuppers, and sometimes it means tapered insulation to build fall into a deck framed dead level.

Seams and terminations are where membranes actually let go. On single-ply TPO and PVC the seams are heat-welded, and a properly welded seam is stronger than the sheet itself. What fails is the perimeter and the transitions, where the membrane turns up a parapet wall, terminates under a coping cap, or wraps an HVAC curb. Those need mechanical termination and counterflashing, not adhesive.

Blisters and bubbles usually mean moisture trapped in the assembly, often from an earlier repair laid over a wet substrate. Covering wet insulation seals the problem in, and the new roof then fails from underneath on somebody else's schedule. If we open a section and find saturated insulation, it comes out.

Older buildings here still carry gravel-surfaced built-up roofing, layers of felt and asphalt with stone on top. At end of life it can be torn off to the deck or, where the assembly is sound and dry, recovered. Which one is right is a judgment we make after opening it up, and we will show you what is under there before committing either way.