Choosing a commercial roofing contractor matters more than choosing the roof system. The same membrane can last decades or fail early depending on who installs it.
That is not a slogan. A commercial roof is assembled on site, in weather, by people, and most of the work that decides its life is hidden by the next layer within hours. Nobody will ever inspect it again. What you are buying when you pick a contractor is the quality of work you will never see, which is why the vetting has to happen before the contract rather than after the first leak.
Check these before anything else
- License: confirm it with your state licensing board, not the contractor’s website
- Insurance: ask for general liability and workers’ compensation certificates sent directly from the insurer
- Manufacturer standing: manufacturers certify installers for their warranties. Ask which manufacturers certify this contractor.
- Commercial experience: ask for three projects of similar size and system, with contacts you can call
- Safety record: ask how they protect workers and tenants on an occupied building
Commercial experience is the item most often waved through. Residential roofing is a different trade with different materials, different details and different risks, and a firm that is excellent on houses may never have welded a seam or flashed a curb. Ask for references on buildings like yours, then call them and ask one question: what went wrong, and how did the contractor handle it. Every project has a problem. How it was handled is the only useful signal.
Where to find candidates worth calling
Start with the membrane manufacturers. Every major one publishes a list of approved installers by area, and that list is filtered for training and trading history before you make a call. Ask other owners and facility managers nearby, because roofing reputation is local and the people who have just been through it know who turned up.
Be careful with the firms that find you. A knock at the door after a storm, a cold call, or a search advert for emergency work will connect you to someone, but it tells you nothing about whether they build good roofs.
Questions to ask in the bid meeting
Ask these in person, on the roof if you can, and listen for whether the answers are about your building or about their company. A contractor who has walked the roof will talk about your drains and your curbs. Decide beforehand which roof system you are asking them to price, so every answer is about the same job.
- Will you take core samples or run a moisture survey before you price the job?
- How will you detail drains, curbs and parapet walls?
- Who will be on site every day, and who is my single point of contact?
- How do you keep the building watertight at the end of each day?
- What exactly does the warranty cover, and who issues it?
Red flags
- A price given without anyone walking the roof
- Pressure to sign the same day
- A large deposit before materials are ordered
- No written scope, or a scope that says only “replace roof”
- Reluctance to put warranty terms in writing
The deposit one deserves a note. Established commercial roofers have credit with their suppliers and do not need your money to buy materials. A demand for a large sum before anything arrives on site is a cash flow signal, and a firm funding this job with your deposit is funding the last job with it too.
Comparing proposals
Line up bids on the same scope before you compare totals. Our guide to replacement cost explains which line items to check, and the replacement guide walks through what a good project looks like from start to finish.
Read the exclusions before the total. A bid that excludes deck repair, equipment disconnection or permits is not cheaper than one that includes them; it is a different document. Then pick on evidence rather than on price alone. The contractor who surveyed the roof, wrote what they found and priced the unknowns as rates is telling you how the job will be run, and that is worth more than the gap between the bids.
Common questions
How many bids should I get for a commercial roof?
Three is the working number for most buildings, and they have to be three prices for the same scope.
- Two gives you no way to tell which one is the outlier
- Beyond four, good contractors start declining to bid against a crowd
- Write the specification first and send the same document to everyone
- Invite firms that want the work, not ones that mostly build much larger roofs
- Ask how many roofs like yours they finished in the last year
Three prices for three different roofs is a list rather than a comparison, and the cheapest item on it is the one that assumed the least. If a contractor declines to bid, ask why.
Does it matter if the contractor is certified by the membrane manufacturer?
It matters a great deal if you want a manufacturer warranty. Manufacturers issue their longer system warranties only on roofs installed by contractors they have approved.
- No approval, no warranty, whatever the contract says
- Approval normally requires training, completed projects and a trading history
- It is a rough filter for competence, necessary rather than sufficient
- Crews vary inside a firm, so ask who the foreman will be
- Ask whether the work is subcontracted, before the job rather than during it
Check the approval yourself rather than accepting a logo, and ask which tier the firm holds, because only the upper ones carry the best warranty terms. Ask too what the manufacturer requires at inspection.
Should I hire a roofing consultant as well as a contractor?
On a large or complicated replacement, often yes. A consultant works for you rather than for a contractor.
- They survey the roof, write the specification and run the bid process
- They inspect the work while the details that decide a roof's life are visible
- The fee is a share of a project you were going to spend anyway
- The case is strongest on complicated roofs and occupied, sensitive buildings
- It is weakest on a small simple roof where the fee is a real share
Make sure the consultant is genuinely independent. Ask in writing whether they take any payment, commission or referral fee from contractors or manufacturers, because a consultant who also sells the roof has the conflict you hired them to check.
What should be in the contract before work starts?
The scope, the schedule, the money and the remedies, with the specification attached as a document rather than summarized in a line.
- Start and completion dates, and payment tied to stages of work
- Unit rates for deck and wet insulation, and who keeps the building watertight
- No extra work and no extra money without your written approval first
- A named approver, so a conversation on the roof cannot commit you
- Proof of insurance current for the whole schedule, and lien waivers on payment
Hold a retention until the manufacturer inspection is passed and the warranty is issued, because that is the only leverage you have at the end. The warranty terms belong in the contract in full.
Should the contractor who installs the roof also maintain it?
Usually yes, and it is worth agreeing at installation rather than afterwards.
- The installer knows the assembly and holds the approval that keeps the warranty valid
- Most manufacturer warranties require periodic inspection anyway
- The conflict is that the firm inspecting is the firm paid to repair
- Require a written report with dated photographs after every visit
- Agree a labor rate, and a value above which work must be quoted and approved
Changing maintenance contractor does not usually void the manufacturer warranty, but check the terms first, because some require an approved firm. Keep every report: it is what proves the inspections happened if you claim.