On a GAF TPO roof, the field of the sheet is rarely where the first leak starts. The trouble begins at the foot of a parapet, where the membrane is clamped under a termination bar and a bead of sealant is all that keeps the top edge shut. Pasadena afternoons bake that bead, the sealant joint shrinks and splits, and the first winter storm runs behind the flashing. GAF offers commercial TPO, asphaltic membranes, polyiso insulation and related components; the roof still depends on how those pieces are selected and assembled. We install, repair and maintain GAF systems on buildings from South Lake Avenue offices to downtown mixed-use blocks, working from the manufacturer's published details and finishing every edge by hand.
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GAF Commercial Roofing Systems in Pasadena, CA
Termination Bars and Dry Sealant Joints
A termination bar is a strip of metal screwed through the flashing into the wall, and it only works if the wall behind it is sound. On older masonry the face of the block crumbles under the screws, the bar loosens, and the top of the membrane peels away one fastener at a time. Sealant laid over the bar is a second line of defense, and in dry heat it hardens and lets go within a few seasons. The repair that holds is to cut back the failed flashing, repair the substrate, reset the bar on solid masonry and tuck the top edge under a counterflashing set into a reglet. Where no reglet can be cut, we form a sheet metal cap that sheds water over the bar. Corners get the same care: each one receives a cut-to-fit corner patch, welded on all sides and checked with a probe, because a corner is where the sheet moves most as the roof heats and cools.
Welded TPO Over Polyiso Board
GAF TPO is a thermoplastic sheet, so neighboring rolls are joined with hot air instead of adhesive. The weld is only as good as the surface it fuses, which means clean, dry membrane, steady machine speed and a temperature set for the morning, because a cool deck with dew on it will starve a weld without showing any sign. We run a probe along every seam edge and rework anything that gives. Under the sheet sits polyiso insulation, and we usually add a cover board so that foot traffic and service visits do not crush it. Fully adhered, mechanically attached and ballasted methods all exist for GAF TPO, and the building decides among them. We state which one we propose, and why, in the written scope before any material arrives. The same welded-seam discipline applies to sheet from Carlisle SynTec or Versico, so a building with mixed roofs gets one standard of detail.
Modified Bitumen Where Traffic Is Heavy
GAF’s commercial RUBEROID line includes SBS and APP modified-bitumen membranes. A layered asphaltic system can suit a roof with frequent service traffic, depending on the deck, details and project specification. A mechanical room that technicians visit weekly, or a roof with a ring of rooftop units, wears a membrane in a way a quiet warehouse never will. A mineral-surfaced cap sheet shrugs off scuffing and dropped tools that would cut a thinner thermoplastic. Self-adhering sheets also let us work without open flame, which matters on occupied buildings with air intakes close to the roof. On a modified bitumen reroof the details still decide the outcome: laps are staggered, flashing plies end high on the wall, and the cap sheet runs into the sheet metal edge with a continuous bead of compatible mastic.
Reflectance Targets on Lake Avenue Reroofs
South Lake Avenue is called the corporate center of Pasadena, and its offices compete in a Tri-Cities market that measured 26.1 percent vacancy at the end of 2025. Across that market, owners are re-tenanting and reroofing older office buildings, and the 2025 California Energy Code puts a floor under what they install: an aged reflectance of 0.63 together with 0.75 emittance, or an SRI of 75 as the alternative. The floor binds a new low-slope roof, and it binds an alteration once the work reaches past half the roof or 2,000 square feet, whichever threshold comes first. A white membrane may meet the initial target, but the aged value is what counts; dust and soot can change the surface over time, so we check the product documentation for the required aged rating. We state in the scope what the reflectance should be once the sheet has weathered, and we lay out the cool roof installation with that figure in mind.
Class A Assemblies and the Foothill Zones
The Eaton Fire of January 2025 burned 14,021 acres near Altadena and Pasadena. Pasadena's Fire Hazard Severity Zones include the Arroyo Seco, the area north and west of the 210, and the upper reaches of Hastings Ranch. Where a property falls in a Very High zone, state rules ask for a Class A covering on every new building and on any existing roof that has more than half its area replaced within one year. Chapter 7A judges the rating for the whole assembly, so the deck, underlayment and insulation have to be a tested combination with the membrane. We select a listed Class A assembly for the project and check the places where embers collect: parapet corners, equipment curbs and vent openings. Clean drains matter too, since burned debris will pond water on a roof that came through the fire.
Cleaning, Drains and Seam Checks
A GAF roof asks for modest, regular care. During planned maintenance and after major wind, we clear drains and scuppers, walk the seams and look at the flashing on every penetration. Heat cycling is hardest on sealed joints, so those are the details we re-seal first when they fail. Walk pads go in wherever service crews cross the roof. Each visit ends with a written report and photos, so an owner or property manager can see what changed and what is coming. Watch for repeated trouble at a failed flashing, because the same detail usually fails again until it is rebuilt.
Commercial Roofing Questions
Can GAF TPO go over an older roof on a Colorado Boulevard building, or does the old membrane have to come off?
A recover is possible when the insulation is dry, the deck is sound, and existing flashing heights still work with the added assembly. We confirm moisture with core cuts or infrared before recommending that path.
Is white TPO or a mod bit cap sheet the better choice on a rooftop full of mechanical units?
Heavy service traffic usually favors the cap sheet, because its mineral surface tolerates scuffs and dropped tools. White TPO can still work with walk pads and equipment rails, and it lowers cooling load through long Pasadena summers. We look at how many people cross the roof and what gets set down on it, then give a recommendation with the tradeoff stated.
What does a GAF roof need to pass a Class A review in a fire zone?
Passing depends on the full assembly, not on the membrane label. California Chapter 7A requires deck, underlayment, insulation and cover to match a listed configuration, and it adds ember-resistant vents and protected drains. We confirm the listing for the specific assembly before we order material, then build to it detail for detail.
How do I know the seams were welded properly after the crew leaves?
Ask for probe checks on every seam edge and photographs of the corners, curbs and terminations. We probe each weld during installation, rework any section that fails and photograph the finished details. Our final walk produces a written report, so a later inspector has something to compare against.
Will a GAF warranty cover problems that come from rooftop equipment work?
Warranty terms come from the manufacturer's written conditions for the specific system on the building, and those conditions usually leave out damage by other trades. For that reason we protect the membrane around equipment and record its condition before and after service visits. Owners should read the actual warranty language for their roof, and we will talk through it with them.
Let Us Look at the Edges on Your Roof
Bring us the building and we will walk the terminations, corners and curbs before anyone quotes a sheet, because those details decide whether a GAF roof lasts. Call to set a visit, or call at any hour when water is already coming through.