Commercial Roof Replacement Cost in LA County

Why commercial roof cost per square foot swings so widely

Per-square-foot pricing is a convenient way to state a bid, not a way to predict one. The same 20,000 square feet can be a clean recover on a sound deck or a full tear-off with wet insulation, new drains and a crane.

• Existing layers: one roof can often be covered; two usually have to come off.
• Moisture: wet insulation must be removed, and it is rarely visible from the surface.
• Deck type and condition: wood panelized decks, steel deck and concrete each need different fasteners and repairs.
• Roof shape: parapets, height changes and many penetrations add labor that a plain rectangle does not.
• Access: hoisting, street closures, tenant schedules and night work all appear in the price.
• Code triggers: cool-roof and insulation rules can change what the new assembly must include.

Recover or tear-off: which one does your building qualify for?

A recover adds a new membrane, usually over a thin cover board, on top of the existing roof. It skips disposal and keeps the building dry during work, so it typically costs less. Building codes generally limit recovers to roofs with a single existing layer, and the old roof has to be dry and well attached.

That is why a moisture survey comes first. Infrared scans at dusk, moisture meters and a few core cuts show how much of the insulation is wet. If wet areas are small, they can be cut out and replaced within a recover. If they are widespread, a tear-off is the honest answer, even though it costs more up front.

How membrane choice changes the budget

A TPO commercial roof cost depends heavily on whether it is mechanically fastened or fully adhered. Fastened systems install faster; adhered systems resist wind uplift and flutter better and often carry different manufacturer coverage. Ask each bidder to name the attachment method in writing.

What does Title 24 add to a commercial reroof?

California's Energy Code (Title 24, Part 6) comes into play once a commercial reroof covers 50% or more of the roof area, and on some low-slope roofs when the work covers more than 2,000 square feet. Most of the San Gabriel Valley is in Climate Zone 9, where low-slope roofs of 2:12 or flatter generally need a cool-roof product.

• Aged solar reflectance of at least 0.63 and thermal emittance of at least 0.75, or an SRI of 75.
• A product listed in the Cool Roof Rating Council directory and carrying its label.
• Exceptions exist, including roof area covered by building-integrated solar panels; your building department decides which apply.

When a low-slope reroof has to add insulation

White TPO, PVC and many coatings meet those numbers easily. The bigger cost question is insulation, since some reroofs also trigger insulation requirements. Confirm both with the city before bids are finalized; see our cool roof installation page for how product ratings are checked.

Under the 2022 Energy Code, replacing a low-slope nonresidential roof generally means bringing roof insulation up to the levels in Table 141.0-C, as the BayREN reroofing guide summarizes. That can add a full layer of polyiso board across the building, which in turn raises curbs, drains and edge metal. The code offers a few relief valves that shape the bid:

• A recover that adds new R-10 insulation above the deck does not have to meet the full table value.
• Where rooftop units will not be disconnected and lifted, insulation can stop at the thickness that keeps base flashing at the manufacturer's required height.
• Tapered insulation may count even where its thinnest areas fall below the prescribed value, under conditions the code spells out.
• Replacing less than 50% of the roof and less than 2,000 square feet keeps the job outside these alteration rules.

The code is revised every three years, so ask the city which cycle applies on your permit date before you compare bids.

Drains, curbs and edges: the line items that surprise owners

The membrane is often less than half the story. Much of a commercial roof's leak risk, and a large share of the labor, sits at its edges and openings.

• Roof drains and overflow scuppers, which may need new bowls, clamping rings or added capacity.
• HVAC curbs that are too short for the new insulation height and must be raised.
• Skylights and smoke vents that are cheaper to replace during the reroof than after.
• Parapet coping and counterflashing, often rusted or pulled loose on older masonry buildings.
• Deck repair, which should be quoted as a unit price per sheet or per square foot before work starts.

What we see on commercial roofs in South El Monte and City of Industry

Our base on Rosemead Blvd sits a short drive from the industrial and retail buildings of South El Monte and City of Industry. The roofs there share a few habits that shape replacement budgets.

• Older roofs recoated several times, so a recover is off the table and the tear-off is heavier than expected.
• Rooftop units added and removed over the years, leaving abandoned curbs and patched holes.
• Drains that clog with dust, causing ponding that softens insulation around them.
• Perimeter metal loosened by the gusty Santa Ana season that runs roughly October through March.

Trade-offs we put in front of owners

A recover saves disposal costs now, but it leaves two systems on the deck. When that roof wears out, both have to come off, so the next owner pays a heavier tear-off. If you plan to hold the building for decades, a full tear-off often prices out closer to a recover over the long run than the first bid suggests.

Insulation works the same way. Adding polyiso lowers cooling loads in a Climate Zone 9 summer, yet it can force curb raises, taller parapet flashing and drain extensions that push the bid up. A thicker membrane costs more per square but tolerates foot traffic from HVAC service better. We price these as options side by side, so the decision is about your hold period and tenants, not a sales pitch.

None of that is visible on a satellite image, which is why we walk the roof and photograph it before quoting.

How to compare commercial reroof bids

1. Make sure every bid covers the same scope: recover or tear-off, membrane type and thickness, insulation type and R-value, attachment method.
2. Check that drains, curbs, skylights and parapet work are either included or priced separately.
3. Look for unit prices on deck repair and wet insulation replacement.
4. Ask how manufacturer coverage and workmanship terms are written, and whether they transfer to a buyer.
5. Look up each contractor's C-39 Roofing license at cslb.ca.gov before signing.
6. Confirm who pulls the permit and schedules the inspection.

How each line on an estimate is usually priced

Getting a commercial roofing number you can budget around

Start with a commercial roof inspection that includes a moisture check, then ask for an itemized written estimate that shows permits and deck repair as separate lines. That gives you a real figure for capital planning and a scope that other bidders can match. Call (725) 745-8803 or request a quote, and we will schedule a walk of your roof.