Commercial Roofing
Grease has a recognizable look on a roof: a dull, tacky stain downwind of a kitchen fan, grit stuck to it, the sheet beneath gone limp, and the nearest drain half packed with the same brown paste. Owners who see it usually already suspect their membrane is the wrong one for the job, and often it is.
PVC, polyvinyl chloride, is the single-ply sheet that stands up best to oils, fats and chemical vapor, which is why it goes below kitchens, food plants and similar exhaust. In Edinburg, TX it also has to take a long heat season and tropical rain. We install and repair PVC, and we begin with a plain question: what lands on this roof, and where does it run?
A PVC membrane is resin mixed with plasticizers and stabilizers, reinforced with polyester scrim and finished with a UV-protective face. Fats, oils, acids and salts that attack other sheets mostly bounce off it. Hot-air welding fuses its seams into one piece, and the material resists fire on its own, which insurers and building officials notice on roofs with cooking exhaust.
What owners pay for that is weight, stiffness and price. PVC also dislikes certain neighbors: asphalt and some foam insulations draw plasticizer out, so a slip sheet or cover board must sit between. On an existing roof we examine those interfaces first, because a sheet resting on the wrong base can fail from underneath while its face looks fine.
Thickness, scrim type and warranty terms vary among PVC products, and the specification should say which is required. A thicker sheet gives more material over the scrim for foot traffic and cleaning, and a lighter one costs less where the roof sees little traffic. We note which gauge is in place on an existing roof from the edge of a patch or a core, and we match or exceed it when we repair.
May to October is the heat-safety season for the Rio Grande Valley. The sheet stiffens, shrinks along seams, tugs at flashings and develops fine cracks at corners where it is stretched. White sheet runs cooler than dark, but it does not escape the cycle.
Walking the roof, we feel for hardness, look for hairline cracking at corners, measure shrinkage at walls and curbs and note dirt baked into the surface. Sheets in that state may still take repairs, or they may have reached the point where a replacement beats a series of patches on cost. A roof tends to age fastest beside its hottest equipment, and the photographs show where the stiffness is concentrated.
Standing water makes it worse. A pond after a tropical downpour leaves the same ring of dirt and algae each time, and the ring holds heat. We time how long water stays after rain and whether the fall to each drain is steady, because roofs that pond age unevenly and fail at the low spot first.
Exhaust fans throw grease onto the sheet, and air currents drop it in the same places every time. Untreated, it softens some coverings, traps dirt that bakes in the sun and creeps toward a drain until it clogs. A containment pan under the fan and a routine cleaning protect any roof, and PVC copes with what slips past.
Food processing and manufacturing sit on the local development group's employer list for Edinburg, with healthcare and logistics alongside. What a particular building sends up its stacks belongs to its mechanical plan, but PVC deserves a place on the shortlist wherever exhaust reaches the roof. At a restaurant roof, we also trace the path from the access point to the fan, because greasy boots spread contamination across the whole roof.
PVC welds at a modest temperature, yet damp, dirty or unevenly heated sheet still bonds badly. On a Valley afternoon the sheet goes soft and the welder is tempted to move fast, and a rushed weld becomes a pinhole leak a season later. Each seam is probed after it cools and the result is written down by location.
Details are harder. At penetrations, inside corners and edges, the roof uses PVC-clad metal and factory-formed pieces welded to the field sheet. Following Dolly's gusts of 50 to 70 mph across Hidalgo County, the weather service advised looking over roof edges, flashings and rooftop equipment, and on PVC that means edge metal, the first feet of sheet at the perimeter and the sealed laps. A membrane puncture repair gets the same cleaning and welding discipline as new work.
The typical repair is a patch welded onto clean, dry sheet. Older sheet may need a mild cleaner to take off an oxidized film before a weld will hold. A patch on sheet that has lost its softener can fail around its rim, so patches are cut with rounded corners and wide overlap, and the sheet beyond the patch is checked for stiffness.
If repairs keep returning to one place, the sheet is rarely the only cause. An infrared scan and a set of cores show whether water has entered the insulation. From there the owner chooses between a local fix and reroofing the affected section, and the commercial roof repair estimate prices both with the evidence beside each.
Foot traffic adds wear. PVC is slick when wet, and a service route that crosses bare sheet collects scuffs and grit. Walk pads along it, set clear of drains, protect the membrane and give technicians surer footing after a morning shower.
Flooding from Hanna in July 2020 is a reminder that roofs have to drain, and grease-laden water moves slowly through a clogged outlet. Edinburg's adopted 2018 IBC and IECC come into play when a replacement changes insulation, and we check them then. Restaurants, food plants, labs and similar buildings are where PVC makes its case, because exhaust and cleaning chemicals are harder on a roof than anything an ordinary office produces.
For owners in Edinburg and Pharr, TPO and KEE are the alternatives we weigh against PVC, judged by the real exhaust, roof traffic and building age. Insulation, deck and the choice between tear-off and recover all feed the answer. The written scope names the sheet thickness, the separation layer, the treatment around each fan and the photographs that will document the finished work.
Below kitchen exhaust, oils or chemical vapor it often is, because it resists what harms TPO. On a plain office roof with little contamination, TPO can do the same job for less.
Asphalt and some foams pull plasticizer out of PVC. A slip sheet or cover board between them protects the membrane from underneath.
When the old roof tests dry and compatible, with a barrier between the two. We scan for moisture first and remove soaked material.
It goes stiff, cracks at corners, shrinks from walls and shows scrim. Patches begin to peel at their rims, a sign the surrounding sheet no longer bonds.
Much less than on most sheets, but built-up grease still holds dirt and clogs drains. Containment at the fan and a cleaning route keep the roof working.