Three bids on the same commercial roof will routinely differ by a third. Almost never because one company is a third better than another.
They differ because they are pricing different roofs. One assumed a sixty mil membrane and one assumed forty five. One included a tear off and one proposed a recover. One priced insulation to current energy code and one matched what is already there. Every one of those is a legitimate approach, and comparing the totals tells you nothing until you know which is which.
So the work of choosing a roofing company is mostly the work of making the bids comparable.
Make them price the same roof
Send every bidder the same written scope, even a rough one, and ask two things: price this, and then tell me separately what you would change and why.
That gives you comparable numbers and their professional judgment in the same document. It also stops the quiet substitution, where one bidder wins on price by assuming a thinner sheet that nobody noticed.
Four lines decide most of the spread:
- Membrane type and thickness, in mils, named.
- Attachment method, and the wind load the assembly was designed for, with the perimeter and corners detailed separately from the field.
- Insulation type and thickness, and whether it meets the current energy code for this building.
- Tear off or recover, and if a tear off, whether deck repair is a lump sum or a unit rate.
That last one matters more than it looks. A lump sum allowance for deck repair is a guess that gets argued about later. A rate per sheet of deck, agreed in advance, means finding more of it does not reopen the whole price.
What to verify, and where
License and insurance. Verify at source. A contractor license is checkable with the state board, and general liability and workers compensation can be confirmed with the insurer directly. A certificate forwarded by email proves considerably less than a call.
Manufacturer approval for the system quoted. This is the one owners skip and it carries real money. Full system warranties are issued through approved installers, so a contractor who is not approved for the system they are proposing cannot obtain the warranty they are describing. One call to the manufacturer settles it.
Who is actually on the roof. Employees or subcontracted crews, and if subcontracted, whether the sub is approved by the manufacturer too.
References on comparable buildings. A company excellent at steep slope residential work is not automatically the right choice for a low slope membrane with forty penetrations.
The three shapes a roofing company comes in
Knowing which you are talking to explains most of what follows, including the price.
The specialist commercial contractor. Low slope systems, manufacturer approvals, in house crews, and a service department that answers when a roof leaks in February. Rarely the cheapest. The right choice on a building where the roof is a capital asset rather than a repair item.
The general roofer. Steep slope and low slope, residential and commercial. Often excellent, and the question is simply how much low slope membrane work they actually do, because the two trades share a name and very little else. Ask what proportion of their work is commercial and ask for references on buildings like yours rather than on any building.
The storm operation. Arrives after weather, works from a truck, offers free inspections and moves on. Some are competent. The structural problem is that they will not be here in three years when something needs looking at under a warranty they arranged.
None of these is wrong for every job. A patch on an outbuilding and a forty thousand square foot membrane replacement are different purchases and it is reasonable to buy them differently.
What a good contractor does that a poor one does not
Four behaviors separate them, and all four are visible before you sign anything.
They open the roof before recommending anything. Core cuts and a moisture survey, because what is under the membrane decides whether this is a repair, a recover or a tear off, and nobody can see it from above. A recommendation made from a walk around is a guess with a price attached.
They tell you what not to do. Every roof produces a list of findings and most of that list does not need money this year. A contractor who separates the urgent from the ordinary is giving you something; one who recommends work everywhere is selling.
They write the specification down. Membrane, thickness, attachment, insulation, cover board, flashing details, edge securement. If it is not written it is not agreed, and the gap gets filled on site by whoever is holding the tools.
They explain the warranty, including what it excludes. Ponding water, for instance, is excluded or restricted by many manufacturer warranties, which tells you plainly what the manufacturer thinks causes failures. A contractor who has read the document will tell you that. One who has not will describe the headline term.
The questions that separate bids
Put these in writing and compare the answers side by side rather than the totals.
- What does your price exclude that another bid might include?
- What warranty term will the manufacturer issue for this exact assembly, and what does it exclude?
- Who inspects the seams, how, and do we get the record?
- How is the perimeter detailed differently from the field?
- What happens if you open the roof and find more wet insulation than expected?
A strong contractor answers all five precisely, and sometimes talks you out of a saving. A bid that cannot explain its own assumptions is the one to worry about, whatever the number says.
Service after the job, which nobody asks about
Almost every conversation about choosing a roofer is about the installation, and almost every problem an owner actually experiences happens afterward.
Ask three questions before you sign.
Who answers when it leaks? A named service department with a number, or the salesperson’s mobile. On a commercial building with tenants, the difference between a four hour response and a four day one is not a roofing matter at all.
Will you maintain it? Most manufacturer warranties require the roof to be maintained, and a surprising number are compromised not by a defect but by years of nobody clearing a drain. A contractor who offers a maintenance program is proposing to protect the thing they just built; one who disappears at handover is leaving the warranty to look after itself.
What happens when another trade damages it? Solar installers, air conditioning technicians, telecoms crews. Most damage to a commercial roof is done by people who are up there for something else entirely, and the sensible arrangement is a written rule that nobody penetrates the roof without the roofing contractor detailing it.
A roof is a twenty year relationship with whoever maintains it and a few weeks with whoever installs it. Buying it the other way round is the most common mistake on this list.
Warning signs
A recommendation made without opening the roof. Core samples and a moisture survey are how anyone knows what is under the membrane. A replacement proposed from a walk around is a guess with a price attached.
Pressure to sign, and large deposits. Materials need paying for; a deposit well beyond that is a different arrangement.
A warranty described but never produced. Ask for the document, not the summary.
Storm chasing. A crew arrives after weather, offers a free inspection, finds extensive damage, and offers to handle the insurance claim. Handling a claim on your behalf is licensed public adjuster work, and a roofer offering it is either unlicensed or describing something else. Get an independent inspection before anyone touches the roof.
What the contract should contain
A proposal is not a contract, and the gap between them is where disputes live.
The specification, in full, including thickness, attachment, insulation and every detail that differs from the field. Attached drawings where the details are unusual.
The schedule, with a sequence rather than just an end date: which sections open when, how much roof is open at once, and what gets closed each night. On an occupied building that sequence is the difference between a project and a disruption.
Unit rates for the unknowns: a price per sheet of deck and per board of wet insulation, agreed before anything is opened. This is the single clause that prevents the most common argument on a tear off.
Who inspects, and what record you get. Seam testing, photographs, and a closeout package with the warranties registered in your name.
Payment tied to milestones, not to dates, and a retention until the closeout package is delivered. A warranty that was never registered is a warranty you do not have, and registration is the step most often skipped once the crew has moved on.
The arrangement that works
An independent condition report first, then competitive bids priced from it.
It costs one inspection fee. In exchange every bid prices the same scope, the findings are evidenced rather than asserted, and nobody assessing the roof stands to win the work. Reading the report a bid should be built on covers what that document needs to contain.
That is also the point at which the money question becomes answerable, because a roof with a known condition can be planned rather than reacted to. Fitting a roof into a capital plan covers the longer view.
Next: choosing a commercial roofing contractor for the selection process in detail, and what drives replacement cost.
Common questions
How do I compare commercial roofing bids?
Make them price the same roof first. Most of the spread between three bids comes from different assumptions about membrane thickness, attachment, insulation and whether the old roof comes off, not from different margins. Until those four match, the numbers are not comparable.
- Membrane type and thickness in mils, stated
- Attachment method, and the wind load it was designed for
- Insulation type and thickness, and whether it meets current code
- Tear off or recover, and who prices the deck repair
- The warranty term the manufacturer will actually issue
Send every bidder the same written scope, even a rough one, and ask them to price it and then separately tell you what they would change. That gives you comparable numbers and their professional opinion in the same document, instead of one bid quietly assuming a thinner sheet to win on price. It also surfaces the bidder who will not commit to a specification, which is itself an answer.
What should I verify about a roofing company?
License and insurance first, and verify both at source rather than accepting a certificate by email. Then the manufacturer approvals for the system being proposed, because a full system warranty usually requires an approved installer and a bid without one is offering a warranty it cannot deliver.
- Contractor license, checked with the state board
- General liability and workers compensation, confirmed by the insurer
- Manufacturer approval for the specific system quoted
- Who is actually on your roof: employees or subcontracted crews
- References on comparable buildings, not just any buildings
The manufacturer approval is the one most owners skip and it carries real money. Full system warranties are issued through approved installers, so a contractor who is not approved for the system they are proposing cannot obtain the warranty they are describing. One phone call to the manufacturer settles it. Approval is also worth confirming for any subcontracted crew, since the warranty follows who installs it.
Should I just take the lowest bid?
Only once you know why it is lowest. Sometimes it is a leaner overhead and a genuine saving. More often it is a thinner membrane, a cheaper attachment, less insulation, or a recover where the others priced a tear off, and those are different roofs rather than different prices.
- Ask what this bid excludes that the others include
- Check the membrane thickness line by line
- Check whether deck repair is a lump sum or a unit rate
- Check the warranty term offered at that specification
- A low bid with a short warranty is being honest about itself
The useful question to a low bidder is not why are you cheaper, which invites a sales answer, but what did you assume that the others may not have. A good contractor answers that precisely and sometimes talks you out of a saving. A bid that cannot explain its own assumptions is the one to worry about. Ask it of the highest bid too; sometimes the premium buys something and sometimes it does not.
What are the warning signs?
Pressure to sign quickly, a deposit well beyond materials, a refusal to put the specification in writing, and a diagnosis offered without anyone opening the roof. Any one of those is reason to pause; two together is reason to stop.
- A recommendation made without cores or a moisture survey
- Large deposits, or payment demanded before work starts
- Reluctance to name the membrane, thickness and attachment
- A warranty described verbally but never produced on paper
- Door knocking after a storm, particularly for replacement
The storm chasing pattern is the costliest one here. A crew arrives after weather, offers a free inspection, finds extensive damage and offers to handle the insurance claim. Handling a claim for you is licensed public adjuster work in Nevada, and a roofer offering it is either unlicensed or describing something else. Get an independent inspection before anyone touches the roof. None of these are rare, and all of them are easier to spot before a deposit than after.
Does it matter who inspects the roof?
It matters a great deal when the inspection leads to a recommendation worth tens of thousands. A contractor who stands to win the work is not independent, which does not make them wrong, but it does mean their assessment should not be the only one behind a capital decision.
- A free inspection from a contractor is a sales visit
- That is legitimate, provided you know which it is
- An independent report can be bid by several contractors
- Independence matters most where a third party reads it
- The test: does the inspector win the work they recommend
The practical arrangement that works is an independent condition report first, then competitive bids priced from it. It costs one inspection fee and it makes every subsequent number comparable, which usually saves more than the fee on the first project it is used for. Paying for one independent report usually costs less than the spread between the bids it makes comparable.