Three proposals come back on a 40,000 square foot roof in Kearny Mesa. They’re spread across a range wide enough that they can’t all be describing the same job, and none of them explains the gap. That spread is almost never about markup. It’s about scope, and reading the scope is the whole skill.
Start with the building, not the bidders
Before you compare contractors, write down what you actually own. Roof area and how it was measured. Number of sections and their slopes. Existing membrane type and how many layers are on the deck. Deck construction. Insulation type and whether anyone has checked it for saturation. Every penetration: HVAC curbs, exhaust fans, vents, conduit, skylights, smoke vents. Drain type and count. Parapet and edge condition. Access route and whether a crane is needed.
That document is what makes bids comparable. Without it, each contractor measures and assumes differently, and you end up pricing three different projects against each other.
The code path differs by building type too. City of San Diego roofing standards route multi-family and non-residential work through California Building Code Chapter 15, while single-family and residential go through the California Residential Code Chapter 9, with local amendments in San Diego Municipal Code Chapter 14, Article 5, Division 15. The permit exemptions that let a homeowner do a like-for-like reroof without a permit apply only to single-family, duplex and townhouse properties. They do not extend to a commercial building. Assume a permit and confirm the requirement with the jurisdiction the building sits in, because each incorporated city administers its own permitting and we could not verify the unincorporated county’s requirements from a primary source.
One rule worth knowing before anyone quotes an overlay: where an existing roof already carries two applications of asphalt shingles or built-up roofing, all layers must come off to the deck before new covering goes on. A bid that proposes a third layer on such a roof is not a cheaper option, it’s a non-compliant one. Our commercial roofing page outlines the system types the roofers in our network work with.
Verify the license before you read the price
California’s roofing classification is C-39, and it covers installing products and repairing surfaces that seal, waterproof and weatherproof a structure against water penetration. Every C-39 contractor is required by Business and Professions Code Section 7125 to keep a Certificate of Workers’ Compensation Insurance or a Certificate of Self-Insurance on file with the CSLB. That’s mandatory, not optional.
License status, complaint history and bond information are all publicly searchable. Run every bidder through the CSLB license check and confirm the license is active, that the classification covers the work, and that the name on the license matches the name on the proposal. A license held by a related entity is not the same as a license held by the bidder.
Then ask for certificates of insurance naming your entity as additional insured, and confirm them with the carrier rather than accepting a PDF. The California Department of Insurance publishes consumer guidance on property claims, worth having on hand in case storm damage becomes a claim mid-project.
On thresholds, Business and Professions Code Section 7048 exempts a single project from licensing only when the aggregate price for labor, materials and all other items comes in under $1,000, the work is casual or minor, and no building permit is required. It also expressly does not apply when work is part of a larger operation, when contracts are divided to get under the number, or when the person advertises as a contractor. No commercial roof project qualifies. Anyone bidding your building without a license is not a cheaper option.
Read the scope for what it leaves out
The cheapest bid is usually cheapest because it excluded something. Look for these specifically.
Tear-off versus recover. Is the existing system coming off, or is a new membrane going over it? Those are different projects with different weights and different code exposure.
Insulation and deck. Does the scope include moisture surveying the existing insulation, and does it name a unit price for replacing saturated insulation and rotted deck found once the roof is open? A bid with no unit price for hidden conditions will produce a change order at whatever number the contractor picks later.
Cool roof compliance. San Diego is Climate Zone 7 under Title 24, Part 6, and Zone 7 is among the zones where the low-sloped cool-roof requirement applies. The thresholds are an aged solar reflectance of at least 0.63 and thermal emittance of at least 0.75, or a Solar Reflectance Index of at least 75, measured on aged values rather than new. The Cool Roof Rating Council weathers products outdoors for three years to produce those aged figures. Confirm each proposed product’s aged numbers, not its initial ones.
Solar-ready and solar clearances. Title 24 solar-ready provisions apply to nonresidential buildings up to three habitable stories and hotel or motel occupancies up to ten habitable stories that don’t install a PV system. Solar Access Roof Area calculations exclude roof areas with less than 70 percent annual solar access and occupied roof areas. Fire code clearances require a six-foot wide access perimeter around roof edges, smoke ventilation options between array installations, and clearances next to skylights, smoke vents and heat vents. If your building has existing arrays or planned ones, those clearances shape the scope and the sequencing.
Fire rating. California Building Code Chapter 7A requires a Class A fire-retardant covering in designated wildland-urban interface areas when more than 50 percent of total roof area is replaced within any one-year period, when a new structure is built, or when a covering is applied in alteration, repair or replacement. That designation matters for buildings in the eastern county and canyon-adjacent industrial edges. Verify the parcel.
Drainage, penetrations and access differ by submarket
San Diego County’s commercial stock isn’t uniform, and neither are the problems. Kearny Mesa and Miramar are dense with mid-century single-story industrial buildings on large low-slope roofs, often with heavy rooftop mechanical loads and interior drains sized for a different code cycle. Otay Mesa and the South Bay skew toward newer high-clearance distribution buildings where roof area per penetration is high.
Sorrento Valley, UTC and the Del Mar Heights corridor mix multi-story office with structured parking, which turns access and staging into a real line item. Downtown adds street closures and crane logistics on top of the roofing work. Coastal buildings in La Jolla and along the Oceanside to Encinitas stretch face salt exposure that goes after fasteners, edge metal and mechanical curbs faster than membrane, so metal replacement scope deserves scrutiny. Inland Escondido, San Marcos and El Cajon put roofs through hotter daily cycling, where thermal movement at seams and terminations shows up first.
Ask each bidder to walk the drains with you, count penetrations against your list, and state the access plan in writing. Our La Jolla commercial roofing and Escondido commercial roofing pages cover how those two conditions differ in practice.
Tenant occupancy and phasing
An occupied building is a scheduling problem before it’s a roofing problem. Ask how the work is phased, section by section, and what the daily tie-in is if rain arrives overnight. Ask about odor and fume control if the system involves hot work or adhesives, and whether tenant HVAC intakes get shut down or filtered during those operations. Ask about noise windows, because a medical tenant’s lease may limit work hours.
Ask who notifies tenants and how far in advance, whether interior protection is included beneath work areas, and how a leak into a tenant space gets handled during construction. Then ask what happens to the schedule if a section opens and the deck underneath is bad. A phasing plan that doesn’t contemplate that isn’t a plan.
Read the warranty documents, not the warranty pitch
Warranty is where proposals diverge most and get compared least carefully. Two structures come up: a manufacturer no-dollar-limit warranty covering labor and material, and a material-only warranty covering the product alone. Those are different instruments with different obligors, and separate from either is the contractor’s own workmanship warranty.
We can’t tell you what any specific program covers, and neither should any contractor’s brochure. The only authority is the actual warranty document from the manufacturer or contractor issuing it. Ask for the full sample document before you sign, not a summary. Read who the obligor is, what triggers coverage, what voids it, what maintenance and inspection you’re required to perform and document, whether ponding water or unrelated trades void coverage, whether it transfers on sale, and what happens if the installing contractor goes out of business.
Manufacturer certification tiers work the same way. Certification programs are administered by the manufacturers themselves, and eligibility for certain warranty types is often tied to them. Verify a claimed certification directly with the manufacturer rather than from a logo on a proposal. Our roof warranty explainer covers the vocabulary in more detail.
When to call us
Commercial roof decisions turn on the condition of the existing assembly, and that requires someone on the roof with a moisture survey, not a bid built off satellite measurements. A documented roof inspection is what makes competing proposals comparable, and it’s the record you’ll want if a warranty claim or an insurance claim comes later. The roofers we connect you with hold active C-39 licenses you can verify yourself. Call us at (760) 750-5557 and we’ll connect you with a licensed local roofer.