Why the Lowest Bid Usually Costs the Most

There is a pattern in residential construction consistent enough to plan around: the lowest bid on a job is frequently the one that finishes most expensive. Not always, and not because contractors are dishonest, but because a low number is produced by a small set of causes and most of them catch up with you later.

Knowing which cause you are looking at is the useful skill.

The four reasons a bid comes in low

Missing scope. The contractor did not price something the others did — permits, demolition, disposal, patching, the electrical work that becomes necessary once a wall is open. The bid is genuinely lower and so is the job it describes.

Thin allowances. Placeholders for tile, fixtures and appliances set below what you will actually spend. The total looks smaller and the difference lands on you at selection time. The contractor allowance guide covers how much this distorts a comparison.

A genuine estimating error. They misread the drawings, misjudged access, or have not done this specific kind of work before. This is the most dangerous version, because the contractor believes their number.

Deliberate underbidding. Win the job at a price that cannot work, then recover through change orders once the space is demolished and you have no alternative.

Only the fourth is bad faith. All four end in the same place, which is why the lowest bid deserves questions rather than gratitude.

Why the lowest bid catches up with you

The mechanism is about negotiating position, and it is worth being explicit about.

At bid stage you have leverage. Three contractors want the work, you can walk away from any of them, and nothing has been committed.

Once demolition has started, that reverses completely. Your kitchen is a shell. The contractor holds the schedule, holds the site, and any change is priced without competition because nobody else is bidding. Bringing in a replacement mid-project means a new mobilisation, a gap of weeks, and a contractor who wants no responsibility for someone else's half-finished work.

A number that was low at signing does not have to stay low. That is the whole of it.

The 20 percent rule of thumb

Once every bid is restated to cover the same scope, a useful diagnostic emerges: compare each against the median rather than against the lowest.

A bid sitting more than about 20 percent below the median of a normalised set is far more likely to be missing something than to have found genuine efficiency. Materials cost roughly the same for everyone, and labour rates in a local market do not vary by a fifth between competent firms. The gap has to come from somewhere.

The bid comparison calculator applies this automatically — it normalises for allowances and excluded scope first, then flags anything that far under. The normalising has to come first, because a bid that is 20 percent low purely because it excluded permits is a different problem from one that is 20 percent low with identical scope.

What to do with the lowest bid rather than reject it

An unusually low bid is a question, not a disqualification.

Ask for a written scope and exclusions list. Ask specifically whether permits, demolition and disposal are included. Ask what the allowances cover and whether they include installation labour. Ask how many jobs they run concurrently.

Sometimes the answer is good: a smaller firm with lower overhead, no showroom, a crew that is not fully booked, or genuine specialisation in exactly this work. Those are real reasons to be cheaper and they hold up under questioning.

More often the answers are vague, and vagueness at bid stage becomes a change order later. The contractor estimate guide covers what a complete document looks like, which makes an incomplete one easier to spot.

Change orders are where the money comes back

If a contractor intends to recover an underbid, this is the route.

Change orders are legitimate and unavoidable on renovation work — opening a wall reveals things nobody could have known. What varies is how they are priced and how much of the original scope quietly turns out to be "extra".

Before signing anything, the contract should state how changes are priced — fixed markup on cost, agreed hourly rate, or a schedule — and require written approval before work proceeds. Without that, changes get priced after the fact, at whatever the contractor decides, on work already done.

The change order guide covers the process in detail. It is the single clause most worth getting right.

The cost of a job that stops

The scenario that turns a saving into a disaster is a contractor who runs out of money mid-project.

An underbid firm can reach a point where finishing your job costs more than they will be paid for it. At that point the rational move for them is to slow down, prioritise other work, or stop. You are left with an unfinished site, a contractor with no incentive to return, and a replacement who will charge a premium to take on work they did not start.

This is why milestone-based payments matter so much. Never be substantially ahead of the work. If the payment schedule has you 60 percent paid at 30 percent complete, the protection has already gone.

What to do instead of taking the lowest number

Normalise first, then decide on everything that is not price.

Once bids are on a common scope and land within a few percent of each other — which is the usual outcome — price has told you all it can. The decision then belongs to references from the last three jobs rather than three chosen ones, verified licensing and insurance, a payment schedule tied to progress, the schedule itself, and how clearly the person communicates when something is inconvenient.

For an independent view of what the work should cost before any bid arrives, the home addition calculator and the basement finishing calculator give square-foot ranges, and the crew hours guide explains how a quantity becomes a labour price. Knowing roughly what a job should take is the fastest way to recognise a number that has not understood it.

The Federal Trade Commission publishes consumer guidance on contracts, deposits and what to verify before work begins.