Skylight Penetration Flashing in Houston, TX

Where Houston Commercial Roofs Actually Leak
Walk almost any flat roof from the Westchase District to the warehouses along the Ship Channel and you will find the same truth: the field membrane rarely fails first. The trouble starts at the openings. Every skylight curb, plumbing vent, gas line, electrical conduit, exhaust fan, and HVAC support is a hole cut through an otherwise continuous waterproofing layer, and each one has to be sealed back up by hand. On a large distribution building near the Port of Houston you can easily count over a hundred of these interruptions. We treat each penetration as its own small roof, because that is exactly how water sees it.
The Gulf Coast makes this work unforgiving. A roof here does not get a gentle rain to test the details. It gets six to ten inches in an afternoon, sideways, driven by tropical wind, the kind of weather that overwhelmed drainage across the region during Hurricane Harvey in 2017. Standing water finds the smallest gap in a poorly lapped flashing and wicks underneath, where it can travel for yards before it ever shows up on a tenant's ceiling tile.
Skylights and the Curb Detail
Daylighting is common on Houston's big-box retail and industrial floors because it cuts lighting load during our long, bright days. But a skylight is also a raised box punched straight through the deck, and the connection between that box and the membrane is where most skylight leaks originate, not the dome or glazing itself. We build or rebuild the curb so its top sits well above the surrounding roof plane, then wrap the membrane up and over the curb, mechanically fasten it at the top edge, and cap it under the skylight's own counterflashing.
On older buildings we frequently find curbs that were flashed flush to the roof, or domes set directly in mastic with no curb at all. Those almost always weep during wind-driven rain. We rework them to a proper raised, fully flashed curb so the water plane stays below the seal. We also check the dome and gasketing, because a cracked acrylic dome that has baked under years of Houston UV will let water in no matter how clean the curb work is.
Pipes, Conduits, and Round Penetrations
Vent stacks, condensate lines, and conduit runs all need flashings sized to the pipe and matched to the membrane system. On thermoplastic and EPDM roofs we use pre-molded pipe boots heat-welded or adhered to the field, then clamped and sealed at the top with a stainless draw band and lap sealant. For odd shapes, clustered pipes, or hot stacks where a standard boot will not fit, we field-fabricate a flashing or build a sealed pourable pocket. We avoid the lazy fix of burying a penetration in a mound of caulk; sealant alone is a maintenance item that fails under our heat cycling, not a flashing.
HVAC Curbs, Equipment Rails, and Roof Supports

Roof planning guidance

Rooftop units are everywhere on Houston commercial buildings, and every one rides on a curb or rail that has to shed water. We flash equipment curbs the same disciplined way we flash skylights, lapping the membrane up the sides and terminating it under the unit's counterflashing. Pipe stands, gas line supports, and cable trays that sit on the roof get sealed bases or are set on properly flashed sleepers rather than pierced through the membrane. When a service contractor adds a new line or a disconnect after the roof is built, that new penetration is often the one that fails next, so we look hard at recent work during any assessment. Why This Detailing Matters on the Gulf Coast Wind uplift. During hurricane season from June through November, negative pressure tugs hardest at edges and around raised objects. A skylight or curb flashing that is not mechanically secured at the top can lift, breaking its seal long before the field membrane is ever threatened.

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Skylight Penetration Flashing in Houston, TX

Hail and impact. Houston sits in a corridor that takes large hail. Acrylic skylight domes crack, and brittle old flashings split on impact, opening paths for the next storm's rain.

Heat and UV. Our intense, year-round sun cooks sealants and accelerates the expansion and contraction that opens lap seams. Details that rely on a bead of caulk instead of a welded or fully adhered flashing have a short life here.

Drainage load. Harris County and HCFCD design rainfall is heavy. When ponding rises around a penetration, the seal is submerged, and any flaw becomes an active leak rather than a slow one.

Houston Energy Corridor commercial buildings

How We Inspect and Repair Flashings

Most calls we get are not for a failed roof, they are for a stain that appeared after a storm. We start by surveying every penetration and skylight, checking curb heights, lap integrity, draw-band clamps, sealant condition, and whether ponding is sitting against any detail. Where the membrane around a penetration is sound, we strip back the old flashing and rebuild just that detail, tying the new flashing cleanly into the existing field with a compatible material so we are not creating a new weak seam. Where a curb is undersized or a dome is shot, we replace the component, not just its flashing.

We keep the work consistent with the roof you already have, whether that is TPO, PVC, modified bitumen, or EPDM, so repairs age at the same rate as the surrounding membrane instead of becoming the next problem. Good penetration detailing is the difference between a roof that quietly does its job through a wet summer and one that drips on inventory every time a squall rolls in off the Gulf.

Roof planning notes

Get Your Penetrations and Skylights Checked

Talk with a Houston commercial roofing team

If you have a recurring leak that the field membrane does not explain, or you simply want the details verified before the next storm season, we are glad to walk your roof and give you an honest assessment of every skylight, curb, and penetration. Reach out and we will schedule a roof assessment at your convenience. Call 713-388-6346 or email info@commercialroofingcontractorshouston.com for help with skylight & penetration flashing | commercial roofing houston, tx in Greater Houston.