Choosing a commercial roofing contractor is a different exercise than hiring someone for a residential job. The stakes are higher, the systems are more complex, and the consequences of a bad hire — a failed flat roof membrane, a flooded server room, a warranty that was never registered — are more expensive to fix.
Here is what to look for, and what to avoid.
Start With Specialization, Not Price
The first filter is simple: does this contractor actually specialize in commercial roofing, or do they do residential too and occasionally take commercial jobs? There is a meaningful difference. Commercial systems — TPO, EPDM, modified bitumen, built-up roofing — require specific training, equipment, and manufacturer certifications that most residential roofers do not have.
Ask directly: what percentage of your work is commercial? What roofing systems do you install most often? A contractor who mostly does shingles and takes a commercial job now and then is not who you want managing a 50,000 square foot flat roof.
Check Manufacturer Certifications
Major commercial roofing manufacturers — GAF, Firestone, Carlisle, Sika, Johns Manville — offer certification programs for contractors. These programs are not just marketing. Certified contractors receive training on installation procedures, have access to extended warranties, and are held to the manufacturer’s quality standards.
More importantly: if a contractor is not certified by the manufacturer whose system they are installing, you likely cannot get a manufacturer’s warranty on the work. That matters for a roof expected to last 15 to 30 years.
Ask for proof of certification, and verify it on the manufacturer’s website. This takes five minutes and eliminates a lot of risk.
Verify Insurance — and the Right Kind
Any contractor can say they are insured. You need to see the certificates. For commercial work, you want:
- General liability insurance — minimum $1 million per occurrence, $2 million aggregate for most commercial projects
- Workers’ compensation — required in most states; protects you if a crew member is injured on your property
- Commercial auto insurance — covers damage from their vehicles on your site
Request certificates of insurance directly from the insurer, not just a copy the contractor hands you. Ask to be named as an additional insured on the policy for the duration of the project. A legitimate commercial contractor will not hesitate at any of this.
References From Comparable Projects
References from residential jobs mean nothing for a commercial project. Ask for references from building owners or property managers who had similar commercial work done — same system type, similar scale. Then actually call them.
Three questions worth asking reference contacts:
- Did the job come in on time and on budget, or were there surprises?
- How did the contractor handle problems that came up during the project?
- Has the roof performed well since installation — any callbacks or warranty claims?
How a contractor handles problems during a job tells you more than a smooth project where nothing went wrong.
Watch: How to Vet a Commercial Roofing Contractor
This informational video covers the due diligence process for hiring commercial roofers, including what questions to ask and red flags to watch for:
Understand the Warranty Structure
Commercial roofing warranties come in two forms, and the difference matters:
- Workmanship warranty — covers installation errors. Issued by the contractor. Typically 1 to 10 years depending on the company.
- Manufacturer’s warranty — covers material defects and sometimes installation. Issued by the product manufacturer. Can range from 10 to 30 years for certified installations.
The best commercial roofing contracts provide both. A contractor who cannot offer a manufacturer’s warranty on the system they are installing is either not certified or is using off-spec materials. Either way, it is a problem.
Get a Proper Written Scope of Work
A quote is not a scope of work. You need a detailed document that covers:
- Exact materials being used — brand, product line, thickness or weight
- Installation method and number of plies or layers
- What happens if damaged decking or insulation is found
- How penetrations, drains, and HVAC curbs will be handled
- Cleanup and debris disposal responsibilities
- Payment schedule tied to project milestones, not just calendar dates
Vague scopes of work lead to disputes. A contractor who is reluctant to put specifics in writing is giving you information about how they operate.
Price Is Last, Not First
Commercial roofing is not a commodity purchase. The lowest bid often means cheaper materials, an uncertified crew, or a contractor planning to subcontract the work to whoever is cheapest at the time. On a job that is expected to protect your building for the next two decades, that is not a trade-off worth making.
Compare bids by scope, not by number. When bids look dramatically different, ask why. Usually the answer tells you everything.