Low Slope & Flat Roofing
TPO, modified bitumen, and built-up roofing systems for residential and commercial low-slope applications. Heat-welded, fully warranted, and built to stay dry for decades.
Flat Roof Expertise, Commercial Grade
Low-slope and flat roofs are a different craft from steep-slope shingle or tile work. They demand different materials, different detailing, and different installer training.
Cornerstone Roofing specializes in TPO (thermoplastic polyolefin) — the modern single-ply membrane that’s become the industry standard for both commercial and residential low-slope applications. Heat-welded seams create a permanently bonded waterproof barrier.
Whether your project is a flat-roofed mid-century home in Santa Rosa, a warehouse in Petaluma, or a commercial tenant improvement in Rohnert Park, we bring the same careful installation practice to every job.
Every Layer Matters in a Flat Roof
A modern TPO roof is a five-layer system. Skip or skimp on any one layer and you’re buying a leak — usually a year or two down the road.
Structural Deck
Existing plywood, OSB, or concrete deck. Inspected, repaired, and prepared for the new system. We never install over wet or damaged decking.
Vapor Barrier
Self-adhered or mechanically fastened vapor control layer that prevents interior humidity from migrating up and condensing under the membrane.
Insulation
Tapered polyiso rigid foam insulation — creates positive drainage slope and delivers R-20 to R-30 thermal performance for energy savings.
Cover Board
High-density fiberboard or gypsum cover board that protects the insulation and gives the TPO a stable bonding surface.
TPO Membrane
60 or 80 mil reinforced TPO sheet, mechanically fastened or fully adhered. Seams are heat-welded into a permanent monolithic membrane.
Every Kind of Flat Roof We Handle
Mid-Century & Modern Homes
Flat-roofed Eichlers and contemporary homes in Santa Rosa, Sebastopol, and Healdsburg. Full tear-off and TPO reroof.
Commercial Buildings
Retail, office, and restaurant buildings across the North Bay. Parapet flashings, rooftop HVAC curbs, scupper and drain integration.
Warehouses & Industrial
Large-span industrial roofs and warehouse projects. Mechanically-attached systems for cost-effective coverage of big square footage.