Quick Answer: You cannot compare prices until the bids describe the same work. In coating work that means six things: preparation grade, the named coating system, dry film thickness, the surface area and exclusions, access, and containment. A bid that omits any of them is not comparable, whatever the number says.
Not by looking at the totals. Three bids on the same building routinely describe three different jobs, and the cheapest is often cheapest because it is doing less — not less well, just less. Until the bids describe the same work, the prices are not measuring anything comparable.
The good news is that coating work has a small number of variables that determine scope, and every one of them is checkable.
The six things that make bids comparable
Surface preparation grade. Named by designation — SSPC-SP6/NACE 3, not "sandblast" or "prep as required." This is usually the largest single cost variable and the most common omission. Two bids differing by a wide margin very often differ here and nowhere else.
The coating system, by product name. Primer, intermediate and topcoat, named individually, with the number of coats. "Two coats of premium paint" is not a specification. Named products can be looked up: their data sheets state the preparation and film thickness they require, which lets you check the rest of the bid against them.
Dry film thickness. Per coat and total, with the method of verification. Film thickness is where a job can be quietly under-delivered without anything looking wrong, and where warranties are most often voided.
Surface area and exclusions. Which elevations, which substrates, and what is deliberately left out — doors, frames, railings, soffits, mechanical equipment, exposed structure. Most bid disputes originate here, not in the price.
Access method, and who provides it. Swing stage, boom lift, scaffold or ladder is a cost and a schedule input. If one bidder assumed lift access and another assumed scaffold, the totals are not comparable and neither is wrong.
Containment, waste handling and disposal. Who contains, what is contained, where the waste goes, and who pays for characterisation and disposal. On a site with lead or chromate in the existing coating, this can exceed the cost of removal.
The seventh, which people read last and should read first
The warranty. Not the number of years — the remedy. Whether it covers labor and access or only replacement material, whether it is prorated, and who inspects.
A bid pairing a shorter term with a labor-inclusive remedy can be worth more than one advertising a longer term that ships you paint.
Where the real risk hides: allowances and unforeseen conditions
The line that decides how a project actually ends is usually the one describing what happens when the surface is opened up and the substrate underneath is worse than anyone could see.
Ask every bidder the same question: what is assumed about the existing coating's condition, was adhesion actually tested, and what is the mechanism and rate if failed substrate is found. A bid that assumes sound substrate without anyone having checked has moved that risk onto you while appearing to be the lower number.
Adhesion testing before bid is inexpensive relative to being wrong about it.
What you can verify without asking the contractor
This is the part most buyers skip, and it costs nothing.
- Licence status. State boards publish free public lookups — California's CSLB, Arizona's ROC, Utah's DOPL, and their equivalents elsewhere. Ask for the licence number and check it yourself: that it exists, that it is active, that the classification covers the work, and whether there is disciplinary history.
- Bond status, which appears in the same lookup in most states.
- Insurance. Request certificates directly, and check the coverage limits, the policy dates, and that your entity is named where your contract requires it.
- Workers' compensation, which is the exposure most likely to reach you if it is absent.
In California, a licensee is required to include the licence number in construction contracts, subcontracts, calls for bid and advertising. If a bidder will not readily supply it, that is itself information.
Red flags that are actually diagnostic
Generic advice says get three bids and check references. These are more specific, and each corresponds to a real mechanism:
- No preparation grade named anywhere in the document
- Coating products described by adjective rather than by name
- A lump sum with no square-footage basis, so nothing can be checked or valued if scope changes
- No mention of containment or disposal on a repaint of a pre-1978 building
- An unusually large deposit relative to the work, or pressure to sign quickly
- A warranty offered verbally, or a term quoted without the document
- No named site supervisor and no stated crew size against a fixed schedule
How to actually run the comparison
Build the table yourself, on your variables rather than on their formats. Put the six items down the side and the bidders across the top, and fill it in from the documents.
The gaps will be obvious immediately, and they are the questions. Send the same written clarifications to every bidder, give them the same deadline, and re-price against the answers. Bidders who respond precisely to a precise question tend to run projects the same way — which is a more reliable signal than a reference list, because you chose the question.
If a bid is low after all six variables are matched, that is a real and useful result. You just have to make the comparison valid before you can trust it.