What Was the Scope of This Flat Roof Project?
This job involved far more than a simple membrane swap. When our crew stripped the existing flat roof on this two-story residential building in the San Fernando Valley, they uncovered structural rot severe enough to require framing repairs before any waterproofing could begin. The owner’s primary goal was a fully watertight roof that could coexist with 3 existing skylights and an operational rooftop solar array, without pulling permits for a system the solar installer had already handled separately.
Flat roofs in Southern California are deceptively low-maintenance in dry years, but average annual rainfall in the Studio City Basin runs 14 to 15 inches, and when a membrane fails, every drop goes straight into the structural assembly beneath it. On this building, that process had been running long enough to compromise multiple joist ends and large sections of decking.
Project Gallery
What Did We Find Once the Old Roof Came Off?
The tear-off revealed joist ends blackened with rot, saturated insulation, and OSB decking that had delaminated across several bays, conditions consistent with a membrane that had been failing for at least several seasons. The parapet sheathing was in similarly bad shape: the old bituminous coating had long since lost adhesion, leaving bare wood exposed to repeated wet-dry cycles.
As visible in the photo above, the damage extended from the deck surface down into the wall framing at the parapet line. Wet insulation batts clung to the cavities below. Addressing only the surface and ignoring that underlying deterioration would have guaranteed a callback within a year or two, so the scope expanded to include full framing replacement in the affected bays.
Across flat-roof jobs in the Valley region, we consistently find that parapet corners and skylight curbs are the first places moisture breaches the membrane, the geometry creates stress points where torch-down or older built-up systems crack earliest. On this building, all 3 skylight curbs showed signs of prior patching that had ultimately failed.
How Was the Structural Rebuilding Handled?
New dimensional lumber was sistered to or replaced the compromised joist ends, and fresh OSB sheathing was fastened across every bay where the old decking had softened or delaminated. The photo above shows the deck mid-rebuild: new pale-gold OSB panels contrast sharply with the weathered framing, making it easy to see exactly how much material was replaced.
As of 2025, California’s Title 24 building energy standards require low-slope roofs on residential buildings to meet minimum solar reflectance and thermal emittance values. The white reflective membrane selected for this project satisfies those requirements, which is relevant for any owner considering future permit work or a sale. A cool roof membrane in Southern California can reduce peak attic temperatures by as much as 20 to 30 degrees Fahrenheit compared to a dark built-up surface, lowering mechanical cooling loads during the region’s long, hot summers.
Once the deck was solid and flat, a self-adhering base layer was applied across the field before the cap sheet was rolled out, the orange-labeled Elastofoam rolls visible in the gallery represent that underlayment stage, used to create a smooth, consistent substrate.
Rolling Out the New White Reflective Membrane
With the rebuilt deck ready, the crew began rolling and securing the white low-slope membrane across the field of the roof, working around the HVAC equipment, penetrations, and solar racking that were already in place. The photo above, timestamped October 20, 2025, shows an early run of membrane being positioned while a crew member clears debris from the parapet area.
Working around a live rooftop solar array requires careful sequencing. The racking feet and conduit runs create dozens of small penetrations and raised obstacles, each of which needs a properly flashed boot or termination bar to maintain a continuous watertight plane. No solar components were removed or modified; the roofing scope was designed to work beneath and around the existing system.
The finished roof, shown in the featured photo at the top of this article, presents a clean white surface with all penetrations flashed and the parapet capped. The reflective membrane will help the building comply with California Energy Commission cool-roof guidance while providing a watertight service life appropriate for a multi-unit property.
The photo above, taken at 2:43 PM on October 20, 2025, captures the parapet sheathing after the old bituminous coating was stripped but before the new membrane was lapped up the wall. The orange OSB and remnant black mastic tell the full story of what the building had been living with.
Get a Quote for Your Flat Roof
If your flat or low-slope roof is showing signs of ponding, interior staining, or failing membrane seams, schedule a roof inspection before the next rain season arrives. Roof Replacement Inc is licensed by the California Contractors State License Board (CSLB) and handles everything from initial tear-off assessment through membrane installation and flashing detail on multi-unit and residential properties throughout the San Fernando Valley. Call us or submit a project inquiry online to discuss your building’s specific conditions.
