Los Angeles County, California
Commercial Roof Replacement in Los Angeles
Whether the old membrane comes off to the deck or stays under a new one is decided by code, and that answer sets the specification before anyone talks about price.
Free, and there is no obligation to go ahead.
- Free roof inspection
Someone comes out, gets on the roof, and tells you what they find.
- The price in writing
A written quote before anyone starts, with nothing to sign on the day.
- Licensed roofers
The roofer who turns up holds a current California license.
- Across Los Angeles County
From the Valley and the foothills to the Westside and the South Bay.
Replacing a low-slope commercial or multi-unit roof means stripping the old membrane down to the deck or covering it with a new one. Code decides which one you get. That decision changes the price and the schedule more than the choice of membrane.
The California Building Code bars a recover where the roof is water soaked, too deteriorated to serve as a base, or already carrying two or more applications. The 2025 edition took effect on January 1, 2026 and renumbered that chapter, so check the section number against the edition your building department enforces. LA County is tighter: Building Code Manual 1512 lets one existing layer stay, and the rest comes off.
Flat and low-slope$12,000 to $30,000
That band covers a roof the size of a house. A commercial deck can sit well above it, and anything bigger gets walked and measured. Costs page.
Count the layers first
Core cuts tell you two things a scan cannot: how many layers are on the deck, and whether the insulation under them is wet. NRCA does not recommend a recover over wet insulation, and says a moisture scan should be confirmed with test cuts. On an LA County roof the layer count decides whether a recover is legal at all, so get it first. The building department inspects once the layers are off, or before new material goes down.
What Title 24 adds
All sixteen California climate zones ask nonresidential low-slope roofs for a three-year aged solar reflectance of 0.63 and thermal emittance of 0.75, or an SRI of 75. Aged means the value measured after three years of exposure. The number printed for a new sheet is a different figure. A membrane without a Cool Roof Rating Council rating defaults to 0.10, so it cannot meet 0.63.
Section 141.0(b)2Bi pulls a re-roof in once more than 50 percent of the roof area or more than 2,000 square feet is altered, whichever is less. On a large roof one phase can cross that on its own, so measure the area you are altering before assuming the job falls outside it.
The roof gets thicker
Table 141.0-C requires R-23ci on roof alterations in Climate Zones 1 to 5 and 9 to 16, and R-17ci in Zones 6 to 8. That board goes above the deck and under the membrane, so it is part of the roof assembly and gets priced with the roof instead of as a separate insulation job. Los Angeles straddles the line: coastal addresses in Zone 6, inland valleys in Zone 9, by ZIP code.
Johns Manville lists R-17 as 2.5 inches of polyiso plus a half-inch coverboard, and R-23 as 3.5 plus a half-inch. That is three to four inches of new build-up above the deck.
Drainage decides how long it lasts
On a replacement the code waives the quarter-inch-per-foot minimum slope where the roof provides positive drainage. The code's definitions chapter puts a number on it: the roof drains within 48 hours of precipitation, with deck deflection allowed for. Standing water is covered on the commercial roofing page. A replacement is the point where it gets corrected, and that correction has to be priced before the membrane is ordered.
LA County Public Works sizes roof drains on 3 inches of rain per hour, without help from overflows. The drain body, the leaders and the overflow piping are plumbing work under C-36. A roofer flashes the drain into the membrane and sets the sump around it. The piping below belongs to the plumber.
Curbs, units and license scope
Base flashing runs at least 8 inches up from the membrane, and new insulation eats that height. NRCA says a recover may not be possible where 8 inches cannot be provided at through-wall details.
C-39 covers sealing, waterproofing and weatherproofing the structure. Lifting a rooftop HVAC unit is C-20 work. Where solar comes off, LA County requires a C-10 or C-46 to put it back, on a separate permit.
Ask which warranty is which
A manufacturer's no dollar limit guarantee and an installer's workmanship warranty are separate pieces of paper, and a bid may include one, both or neither. Ask which of the two is on the table before you compare prices. Johns Manville, as one example, issues NDL guarantees only through contractors it has designated. Ask whoever is bidding your building whether they hold that designation, and the manufacturer will confirm it.
JM excludes damage from improper drainage on every system except PVC and TPO, damage from foot traffic and stored material, and pre-existing materials left under a recover. On a flat deck read the drainage exclusion twice. The standing water the county sizing rules are written around is the same water the guarantee will not cover.
What to ask before you sign
- How many layers are on the deck, and what did the core cuts show?
- Which climate zone is this address in, and what R-value does that set?
- Which warranty comes from the manufacturer, which from the installer, and how long does each run?
Get the layer count and the drainage plan in writing before anyone quotes. The visit is free, because the layer count and the drainage only show up on the roof. The roofer who turns up holds a current California license and hands over the CSLB number.
The offer
$500 off a new roof, 10% off any repair
Start online and it is attached to your request, with nothing to remember.
- We get on the roof, and into the attic if that is where the answer is
- You get photographs of whatever we find
- The price in writing, with nothing to sign on the day
Where we work
Across Los Angeles County
Tell us what is going on
A description is enough to start. We will come out, look at the roof properly, and give you the price in writing.