When a business owner in Phoenix, Arizona, sends identical plans to five contractors and receives five wildly different numbers, the variation often stems from project fit and interpretation gaps rather than contractor malfeasance. Mike Marden, a registered architect and licensed general contractor and founder of WDS, a Phoenix-based integrated design-build firm, has observed this dynamic for decades. According to Marden, the spread in bids almost always traces back to specific gaps, and once owners understand them, comparing bids becomes far easier.
The bidding process itself introduces room for interpretation. If bids are based on a preliminary walkthrough rather than a finished, detailed set of plans, contractors may envision vastly different scopes. "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." Even with full plans, the time and attention a contractor plans to spend on supervision, management, and overhead directly affect the final price, leading to divergence.
One of the most common reasons bids spread apart is that some contractors visit the job site and some do not. "They have the drawings or the specs, but they don’t go out and look. They don’t walk the job site," Marden says. If two out of five bidders skip that step, they are pricing a different project than the others, despite receiving the same paperwork. Special instructions, separate exhibits, or desired exclusions can also be missed by contractors who are not reading closely, widening the spread 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. "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 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. Some contractors provide a daily on-site quality control supervisor dedicated to the project, while others may just have someone occasionally driving by to check the job site.
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. Taking a look at what kind of projects are in the photographs on their website is another good indicator of their true experience. 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.
