When a business owner in Phoenix sends identical building plans to five contractors, the returned bids often bear little resemblance to one another. According to Mike Marden, a registered architect, licensed general contractor, and founder of WDS, a Phoenix-based integrated design-build firm, this wide variation is rarely due to contractors trying to take advantage of owners. Instead, it stems from project fit and the room for interpretation inherent in the bidding process. Marden has observed this dynamic from both sides of the table for decades and says the spread in numbers almost always traces back to a handful of specific gaps. Once owners understand these gaps, comparing bids becomes far more manageable.
The bidding process itself often introduces variability before a single number is written down. If bids are based on a preliminary walkthrough rather than a finished, detailed set of plans, there is already room for wildly different interpretations. “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.” During 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 visit the actual job site conditions 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,” 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, which widens 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. 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. For owners, this approach not only reduces the risk of costly surprises but also ensures that the selected bid truly reflects the scope and quality of work expected.
