How We Diagnose a Flat Roof Before Anyone Touches It
A roof asset survey comes first: we walk the field, probe the substrate, and take moisture readings. That tells us whether water has wicked into the insulation or stayed inside the membrane.
Ponding water around a scupper reads differently than a blistered, buckled seam near a parapet. Our roof inspection report photographs each defect and ties it to a line-item estimate.
Granule loss, alligatoring, and UV degradation on a granulated cap sheet point to end-of-life wear rather than one leak. Rot and decay show up as a soft spot underfoot, and a sagging roofline means the rafters or truss are carrying water weight.
Flat Roofing Systems We Repair and Install
System selection drives warranty length, reflectivity, and how the assembly handles thermal cycling. Here is what we see most on low-slope commercial buildings.
- TPO membrane is a single-ply sheet with heat-welded seams, which suits retail and restaurant roofs that see grease and foot traffic.
- EPDM rubber roofing is a synthetic rubber sheet that shrugs off UV and standing water, so it fits older buildings with minimal pitch.
- PVC single-ply resists animal fats and chemicals, which is why commercial kitchens and labs often specify it.
- Modified bitumen is an asphalt-based sheet we torch or self-adhere, and it works well on roofs crowded with penetrations.
- Built-up roof (BUR) assemblies alternate roofing felt and hot bitumen; they patch cleanly but install slowly and add dead weight.
We install and service systems from Carlisle SynTec, GAF EverGuard, Firestone, Johns Manville, and Versico. A reflective roof coating can restore waterproofing on a sound membrane without a tear-off.
What Tear-Off, Recover, and Overlay Really Involve
Not every flat roof needs a tear-off. When the existing membrane is sound and the deck is dry, a recover or overlay adds a layer without sending a dumpster of debris off the site.
On a full tear-off we strip to the decking, check the plywood or OSB sheathing for rot and sag, then install new insulation and membrane over a clean substrate.
Seams go down in staggered courses with the correct lap, and fasteners are driven flush so no screw sits proud of the sheet.
Crews work off ladders and scaffold with a safety harness, and the truck carries a roofing square, nail gun, air compressor, pry bar, and roofing shovel.
What We Check on Every Low-Slope Roof
A flat roof fails at its edges and penetrations long before the field area gives out. Our checklist walks the perimeter before we price anything.
- Ice-and-water shield protects the eave and valleys where water backs up, and synthetic underlayment covers the rest of the field.
- Drip edge, eave, fascia, soffit, and rake details keep runoff off the wood, and a soft fascia usually means a gutter has been overflowing for years.
- Gutter and downspout runs get flushed and tested, because a clogged scupper pushes ponding water back across the membrane.
- Step flashing, counter-flashing, apron flashing, and chimney flashing get probed for gaps where a crew hand-sealed instead of rebuilding.
- Pipe flashing and the boot flashing around each vent stack are the most common leak points we find on commercial rooftops.
- Ridge, ridge cap, and ridge vent matter only where a pitched section meets the flat roof, but they fail loudly when they do.
- Skylight curbs, dormer walls, and chimney walls get checked for cracked lens seals and loose fasteners that let water wick behind the frame.
- Parapet, coping, and scupper details decide where water leaves the roof, and where it sits when they clog.
- Insulation and roof deck get probed for moisture content, because wet insulation rots plywood or OSB sheathing from underneath.
- Fasteners, screws, and nails are checked for backing out, and an overdriven screw becomes a leak the moment the sealant fails.
- Sealant and caulk beads at terminations are cut out and replaced, since mastic and roof cement dry, crack, and peel within a few seasons.
- Snow guard and anchor points get inspected where crews walk the roof, because foot traffic tears membrane around hardware.
Under the deck, rafters, trusses, and joists carry the load, and a sagging ridge beam or failing purlin shows up as a dip in the roofline.
Where a flat section meets a pitched roof, three-tab shingle, architectural shingle, laminated dimensional shingle, wood shake, cedar shake, slate, clay tile, concrete tile, or a standing-seam metal panel each tie in differently.
Copper, aluminum, and composite flashings handle most of those transitions, and a corrugated panel roof relies on battens and counter-battens to build its drainage plane.
Old tar, pitch, and tar paper work from an earlier roofer has to come out before anything new goes down.
Hip, gable, mansard, and gambrel profiles drain at different rates, and a canopy, awning, or deep overhang collects debris against the flashing and the verge.
Local Conditions, Timelines, and Costs
Hot, dry summers and wildfire risk push us toward Class A assemblies, and we avoid open torch work during red flag warnings. Morning fog leaves the membrane wet until mid-morning, so adhesive and coating schedules shift.
Winter storms drive water against parapets and through scuppers that drained fine in July. We check overflow drains, coping, and downspouts before the first rain and keep tarp stock for emergency roof repair calls.
Ice dams are rare here, but a cold snap in the hills can still back water under an eave. Ventilation matters as much as membrane, since an attic fan or soffit vent that exhausts into a flat cavity adds moisture the deck cannot shed.
A missing vapor barrier lets that moisture condense on the underside of the roof deck, where it rots the sheathing quietly for years.
A single-section repair usually takes one day, while a full commercial replacement runs three days to two weeks. Cost drivers are system choice, how much wet insulation we remove, and how much decking needs replacing.
Low-slope manufacturer warranties generally run 15 to 30 years on a no-dollar-limit basis, and building code plus Title 24 cool-roof rules decide which membrane qualifies. A coating buys time, but it does not restore weatherproofing once the membrane has split.
