Flat roofing in Los Angeles
A flat roof is never truly flat. It has a slight slope that carries water to drains, scuppers or the roof edge, and it relies on a continuous sealed membrane instead of overlapping shingles or tile. Most flat roof problems come from water that stands instead of draining, and from flashing at walls and edges. We install, replace and repair flat roofs on homes, garages and apartment buildings.
- Service
- Flat roofing
- Contractor
- LA General Builders, CSLB Lic #1044686
How a flat roof keeps water out
A pitched roof sheds water quickly, so it can be made of overlapping pieces. A flat roof drains slowly, so it has to be a sealed surface with no gaps: a membrane with welded or bonded seams, turned up at the walls and sealed at every drain and pipe. The membrane is only as good as those seams and edges.
Drainage is the other half. The roof has to slope enough to move water to the drains or scuppers, and those have to stay clear. Where the structure has settled and water stands, a new membrane alone will not solve it. We look at drainage on every flat roof job and correct the slope where it is needed.
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A sealed membrane
A continuous membrane, turned up at the walls and sealed at every drain, pipe and edge.
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Sloped to the drains
A flat roof needs a slight slope so water runs to the drains or scuppers.
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Standing water
Water that stays more than two days after rain wears the roof out faster. We correct the slope.
Signs a flat roof needs attention
- Water still standing on the roof two days after rain
- Blisters, bubbles or ridges in the roof surface
- Seams that have opened or lifted
- Cracks in the surface or in the coating
- Flashing pulling away from parapet walls
- Stains on the ceiling below, or on walls just under the roofline
How the job runs
The same steps on every job, from the first look at the roof to the final inspection.
Inspect and check drainage
We walk the roof, check drains and scuppers, and mark where water stands.
Written scope and price
The scope says whether the roof can be repaired or restored, or needs a new membrane, and why.
Remove the old roof
Where the roof is being replaced, the old membrane comes off and we check the deck beneath it.
Repair the deck and correct the slope
Rotted decking is replaced. Where water stands, we build up the slope so it drains.
Install the membrane
The new roof system goes down, with flashing carried up the walls and sealed at every drain, vent and edge.
Test, clean up and inspection
We check the drains and seams, clear the roof and the ground, and meet the inspector for the final.
Flat roof systems
| Option | Best for | Good to know |
|---|---|---|
| TPO membrane | Most flat roofs on homes and apartment buildings | A white, heat-welded single-ply sheet that reflects the sun. |
| Modified bitumen | Smaller roofs, garages and roofs with foot traffic | A tough, multi-layer asphalt-based roll roofing with a granule surface. |
| Roof coating | Restoring a flat roof that is worn but still sound | A liquid-applied coating over the existing roof. Not a fix for a roof that is wet underneath. |
| Tapered insulation | Roofs where water stands | Sloped boards under the membrane that carry water toward the drains. |
What sets the price
- Roof area and how easy the roof is to reach
- Whether the old roof has to be removed
- The roof system you choose
- Drainage work, such as added slope, new drains or scuppers
- The length of parapet wall and the number of penetrations to flash
- Deck repairs under the old roof
Permits and inspections
Most full re-roofs need a building permit from your city or the county, and the rules differ from one building department to the next. We confirm what applies to your address, pull the permit and meet the inspector, so the finished roof is signed off. California's energy rules also set reflectance requirements for some low-slope re-roofs, and we check what applies to your building.
Questions homeowners ask
Is standing water on a flat roof a problem?
Water that clears within a day or two after rain is normal. Water that stays longer wears out the roof faster and points to a drainage problem worth fixing.
Can a flat roof be coated instead of replaced?
Sometimes. A coating can extend the life of a roof that is worn on the surface but dry and sound beneath. If the layers below are wet, a coating traps the moisture, and replacement is the right job.
Which flat roof system is best?
It depends on the size of the roof, how much foot traffic it gets and what is on it. We recommend a system after seeing the roof and explain the reason.
Can I use my flat roof as a deck?
Only if it is built for it. A roof deck needs structure designed for the load and a walking surface that protects the membrane. As general builders we can design and build that.
Get a price for your roof
Tell us about the roof and we will call you to set up a visit. Or call now and talk to an estimator.
818-741-5451See a price range in about a minute
LA General Builders, 8728 Zelzah Ave, Northridge, CA 91325
CSLB Lic #1044686