Business owners in Phoenix, Arizona, frequently send the same set of plans to multiple contractors and receive bids that vary so widely they seem to describe different buildings. According to Mike Marden, a registered architect and licensed general contractor and founder of WDS, a Phoenix-based integrated design-build firm, this discrepancy is rarely due to contractors trying to take advantage of owners. Instead, it stems from project fit and the considerable room for interpretation inherent in the bidding process itself.
Marden, who has observed this dynamic from both sides of the table for decades, explains that the spread in numbers almost always traces back to a handful of specific gaps. The first gap emerges when bids are based on a preliminary walkthrough rather than a finished, detailed set of plans. “There’s a lot of interpretation going on there,” Marden says. “Their imaginations are running wild, or the owner giving them information is presenting it a little differently each time.” On a site walkthrough, what one contractor sees, hears, and is told can differ from what the next one experiences, and that alone can start the variation. Even with a full, specific set of plans, numbers can still diverge based on how much time and attention a contractor plans to spend on the project. That difference shows up directly in the final price as adequate or inadequate supervision, management, and overhead.
One of the most common reasons bids spread apart, according to Marden, is that some contractors inspect the actual job site conditions while others do not. “They have the drawings or the specs, but they don’t go out and look. They don’t walk the job site,” he says. If two out of five bidders skip that step, they are pricing a different project than the other three, even though everyone received the same paperwork. Special instructions, separate exhibits, or desired exclusions can also get missed by contractors who are not reading closely, widening the spread even further.
Owners often assume the lowest number is the safest choice, but Marden says the real problem is usually that the bids were never in a comparable format to begin with. “Please break these down into separate scopes,” is the basic ask he recommends. Without that breakdown, markups like overhead, insurance, and taxes stay hidden inside a single lump-sum number, making it impossible to know what is actually being paid for. For larger projects, Marden suggests separating a project into its logical phases first, such as interior work versus site work or landlord work versus tenant work, and then breaking each trade out individually. That includes asking every bidder to detail their supervision costs specifically, since Marden considers supervision one of the biggest drivers of price differences between contractors.
A bid that looks too good to be true is often exactly that, and Marden says the first place to look is not the number itself but who submitted it. “If it looks very thorough, you’re going to have to dig deeper. If it’s just a one-liner or it looks like it’s put together quickly, then I think we’re on to something,” he says. From there, Marden recommends checking whether the contractor has actually done this type of project before, since a company skilled at building houses is not automatically qualified to build a medical office or restaurant. He also flags a missing project schedule as a warning sign, since a contractor who hasn’t accounted for the full duration of the job may not have built enough into their number to cover it.
The clearest way to prevent this kind of confusion in the first place, Marden says, is to set the terms before bids come in: state the expected project duration or ask each contractor to submit a timeline or schedule, and require a standardized, itemized form that breaks out insurance, taxes, and overhead and profit separately from trade costs and from project personnel and job site costs. Getting everyone on the same playing field before the numbers arrive is what actually makes an apples-to-apples comparison possible.
