Grease, Kitchens and Rooftop Exhaust
Playhouse Village packs more than 45 restaurants, bars and cafes into 32 blocks, and Old Pasadena stacks offices above ground-floor dining across 22 blocks. Wherever a kitchen vents through the roof, the fat that leaves the fan settles on the membrane around it. Grease softens many roofing sheets, swells the seams nearest the fan and invites a leak that appears in the dining room below. PVC tolerates most of that exposure, so it is a common answer on restaurant roofs and on mixed-use buildings with a kitchen at street level.
The sheet is only half the answer. A splash guard on the fan curb, a drip tray under the discharge and a walkway pad where cooks and technicians climb up all keep fat off the roof surface and save the owner from cleaning it off later. Where the exposure is severe, a KEE membrane is worth considering instead, and we say which one suits each building in the scope.
Flame-Free Work Beside Hospitals and Labs
Some roofs cannot tolerate smoke, fumes or open flame near their air intakes. Huntington Hospital on California Boulevard, the San Gabriel Valley's only Level II trauma center, has towers added in 1998 and 2008 and an emergency department enlarged in 2014, so the campus grew in stages. PVC is welded with hot air, with no torch and no asphalt kettle, and that makes it a straightforward fit for hospital roofing and for laboratory buildings, the kind of newer research space Caltech has added beside its older halls.
Quiet matters as well as air. We stage materials at the edge instead of crossing occupied floors, schedule noisy work around procedures and tenant hours, and keep a flagged route for access to every curb. The HeArt District near Huntington Hospital mixes medical and arts uses, and a reroof there is planned around the people inside from the first walk of the roof.
Foothill Fire Rules and Ember Exposure
Fire resistance is built into PVC chemistry, but it is not the whole story. In the Very High zones of Pasadena's foothills, state rules require a Class A covering when more than half of an existing roof is replaced in a year, and they ask for ember-resistant vents and gutter debris protection as well. In January 2025 the Eaton Fire forced the Jet Propulsion Laboratory to close and evacuate. The lab escaped with minor wind damage and nothing structural, but the forecasts ahead of that fire called for Santa Ana gusts of 60 to 80 mph, and that is the wind and ember load a roof edge or rooftop unit near the foothills has to be built for.
We read the whole assembly before specifying PVC in those zones, because the deck, the insulation and the cover board all take part in the rating. Embers find an open lap, an unscreened penetration or an unclosed edge long before they touch the middle of a sheet, so detailing at those points matters more than the membrane brand on the data sheet.
Commercial Roofing Questions
Is PVC worth the extra cost over TPO on a building with a busy kitchen?
Where fans put fat on the roof, usually yes, because a membrane that swells or softens around the exhaust becomes a repair bill every few years. TPO still suits plenty of roofs, including those without cooking exhaust, and we are glad to put a TPO roof on a building where it makes sense. The exhaust layout, the roof traffic and the planned life of the building make the call between them.
How can I tell whether an older PVC roof has lost its plasticizer?
Press and gently bend a loose edge of the flashing or lap on a warm afternoon. A healthy sheet flexes without a sound, while a depleted one feels stiff, shows fine cracks on the fold and may curl away from the lap. We also measure shrinkage at the walls, where aged sheet has often pulled back from the base of the flashing and left a gap.
Can a new PVC sheet be welded to the old one?
Only after the old surface is cleaned and a test weld proves it will take. Aged PVC carries a film of dirt and migrated plasticizer that keeps a fresh weld from fusing, so we scrub, solvent-wipe and weld a small sample first. If the sample peels, the lap is mechanically fastened and covered, or the section is replaced outright.
How does PVC cope with Pasadena winter storms and standing water?
Water does not harm fused seams, but standing water carries dirt that dulls the surface and loads drains. The San Gabriel Mountains lift winter storms, so Pasadena collects about 6 inches more rain a year than downtown Los Angeles, and February averages 3.9 inches. We slope tapered insulation toward the drains, add a cricket behind each unit and clear scupper boxes before the first big storm.
What does PVC need after installation to stay in good shape?
Mostly attention. Wash the surface when it is visibly dirty so reflectance stays high, keep grease and debris off the sheet around exhaust fans, and have the flashing and welds looked at once a year and after any heavy storm. A short visit that finds a lifted lap costs little, and the same lap left through a wet winter can soak the insulation beneath.
