A commercial roof is a working surface. It carries equipment, collects water and sits over people who cannot stop their day. Replacing one starts with a look at the layers and the drains, then a plan for the order of work.
What commercial roofs are made of
Low-slope commercial builds include built-up roofing with layered felts, modified bitumen sheets, and single-ply membranes such as TPO, PVC and EPDM. Metal panels and tile cover the steeper roofs on smaller commercial and multi-unit buildings.
Which system fits depends on the deck, the drainage and what stands on the roof. A core cut tells us the layer count and whether the insulation has stayed dry.
Units, curbs and drains
Rooftop units sit on curbs, and every curb is a place water can enter. In a reroof the curbs are raised, flashed and tied into the new membrane. Units that need lifting are planned with the building contact. Drains, scuppers and overflow outlets are checked for fall and rebuilt where water would sit.
We list each unit, curb and drain in the scope with its detail, so there is no surprise on the day.
What a commercial reroof includes
- Roof survey and core cut to confirm layers
- A phasing plan for occupied buildings
- Curbs, units and penetrations written into the scope
- Drains and scuppers checked for fall
- New membrane or metal system to the maker's instructions
- Edge metal, parapet flashing and cleanup
Signs a commercial roof needs replacing
- Leaks that return in new places after each fix
- Ponds that remain after a dry week
- Seams opening along the membrane
- Wet insulation found under the surface
Cool roof values for nonresidential work
For nonresidential reroofs in the City of Los Angeles, LADBS points to Title 24 Section 141.0(b)2B (LADBS, 2026). Low-slope nonresidential roofs in zones 4 and 6 through 15 can follow the state values, SRI 75 or aged reflectance 0.63 with emittance 0.75 (California Energy Commission, 2022).
Product listings in the CRRC directory show the aged numbers. We check the listing before a membrane is ordered.
Phasing and tenants
A building that stays open can be reroofed in sections. The roof is divided, one area is opened and closed in a day, and the work moves on. Noise, dust and access routes are agreed ahead with the manager.
The permit comes first. A City of Los Angeles address goes through LADBS (LADBS, 2026). In County jurisdiction, covering over an old roof is allowed only with one layer, adequate framing and a sound, dry deck (Los Angeles County Public Works, 2025).
Commercial roof questions
How do rooftop units and curbs fit into a reroof?
Each unit sits on a curb that gets raised, flashed and tied into the new roof. Units may need to be lifted or shut down. The scope names every curb.
What is a no dollar limit warranty from a roof maker?
A no dollar limit warranty is a roof maker's term for a system warranty without a cap on the covered cost. Coverage differs by maker and by system, so ask for the document itself and read its conditions.
Can a building stay open during a reroof?
A roof can be replaced in sections so the building keeps running. We plan the order of work, access and noise with the manager before the first day.
Does a commercial reroof have to meet cool roof values?
For nonresidential work in the City of Los Angeles, LADBS points to Title 24 Section 141.0(b)2B (LADBS, 2026). The state's low-slope table sets 0.63 aged reflectance, 0.75 emittance or SRI 75, for zones 4 and 6 through 15 (California Energy Commission, 2022).
What type of roof do commercial buildings have?
Low-slope roofs are built-up, modified bitumen or single-ply (TPO, PVC, EPDM). Smaller commercial and multi-unit buildings can carry metal or tile on a steeper slope.