# Why do construction bids for the same project vary so much?

**Short answer:** Construction bids on the same drawings vary because the bidders are not pricing the same scope. The low number is usually low because something was excluded: work the drawings implied but never specified, allowances set unrealistically, general conditions left thin, or optimistic assumptions about the site. Normalize the bids before you compare them.

## Key facts

| Fact | Value | Source |
| --- | --- | --- |
| Typical spread | 20% to 40% between high and low on custom residential |  |
| Most common cause | Scope exclusions, not labor rates |  |
| Second most common | Allowances set to win the job |  |
| Bid versus estimate | A bid is an offer to perform; an estimate is a forecast |  |
| What fixes it | A normalized comparison on one written scope |  |

## Start from the assumption that the low bid excludes something

Two builders receive the same drawings on the same day and return numbers a
third apart. The instinct is to conclude that one is expensive and one is
efficient. Occasionally that is true. Far more often, they priced different
projects, because the drawings did not fully define the project and each bidder
resolved the gaps in their own favor.

A set of drawings is never complete. There is always work that the documents
imply without specifying: how the tile meets the plaster, what happens at a
transition the detail sheet never drew, which trade owns backing and blocking.
Every bidder decides what to do with those gaps. Some carry them. Some exclude
them in a sentence on page four. The excluded version is cheaper, and it is
cheaper because it is smaller.

That is the whole answer, and everything below is the anatomy of it. The
question worth asking is not "why is this one higher." It is "what did each of
these bidders assume, and can I see it written down."

## The six places numbers actually diverge

### Scope gaps

The largest single contributor. A drawing set that shows a wine room without
specifying cooling, or a site plan showing a driveway without a section, invites
two legitimate but incompatible interpretations. The bidder who carries the
cooling unit looks expensive next to the bidder who did not see one specified.

### Allowances set to win

Allowances are supposed to be a placeholder for undecided selections. Used
honestly they are a reasonable device. Used competitively they are a discount
that expires: a tile allowance set well below what the client will actually
choose produces a low contract sum and a predictable series of adjustments once
selections begin.

### General conditions

Supervision, site office, temporary power and water, protection, cleanup,
dumpsters, safety, and the project manager's time. This is the cost of running
the job rather than building it, and it scales with duration. A bidder with a
short assumed schedule carries less of it. If the schedule was optimistic, the
general conditions were too.

### Assumptions about the site

Soil, groundwater, existing utilities, access, staging space and neighbor
conditions. On a hillside or a tight infill lot these decide the excavation and
retention scope, which is why two bidders can differ by a very large figure on
site work alone. A bidder who assumed no engineered retention and one who
carried it are not in the same conversation.

### Contingency, escalation and risk

Some bidders carry contingency inside the number and some do not carry any. Some
price material escalation over a long build and some price today's cost. Neither
approach is wrong, but the two produce different totals for identical work, and
only one of them will hold.

### The estimate that is calling itself a bid

An estimate is a forecast of probable cost. A bid is an offer to perform defined
work for a stated sum. They look similar on paper and behave completely
differently once a contract exists. If the document does not identify the exact
drawing set and revision it prices, it is an estimate regardless of what it is
titled.

## Normalizing bids onto one basis

You cannot compare numbers until they describe the same work. Rebuilding them
onto a common basis takes an afternoon and is the highest return work in the
whole selection process.

- Identify the exact drawing set, revision and date each bid priced.
- List every exclusion from every bid, then apply all of them to all bids.
- Reset every allowance to one agreed value across all bidders, using real
  pricing from actual selections rather than the bidder's placeholder.
- Separate general conditions and fee from the trade costs so they can be seen
  as their own line.
- Confirm each bidder's assumed schedule, since duration drives general
  conditions.
- Confirm each bidder's site assumptions, especially excavation, retention,
  shoring and utility work.
- Check whether contingency and escalation are inside the number, outside it, or
  absent.

Once that is done, the spread usually shrinks dramatically. What remains is the
real difference: fee, overhead, buying power and how the builder prices risk.
That difference is worth paying attention to. The one you started with was
mostly noise.

## What to ask each bidder before you decide

**"What did you exclude, and why?"** The answer tells you how carefully the set
was read. A bidder who names three specific gaps has done the work. A bidder who
says nothing was excluded has either not read the drawings or is about to write
change orders.

**"Show me general conditions as its own line."** If it is buried in a
percentage or absent, the number is incomplete. This line is also the fastest
way to see whether the assumed schedule is honest.

**"What are you assuming about the soil and the site?"** Ask for it in writing.
Site assumptions are where the largest post-contract surprises live, and a
geotechnical report resolves most of them before anyone signs.

**"Which numbers are allowances, and what do they buy?"** Then go price two or
three of them yourself. It takes an hour and it recalibrates the entire bid.

**"What is your fee, and what does it cover?"** A builder who will state fee
plainly is a builder who expects the relationship to survive scrutiny. That
posture matters more over an eighteen month build than any single line item, and
it is worth weighing alongside how the firm actually works, which is what an
[about page](/about) and a reference call are for.

## What the comparison is really measuring

By the time bids are normalized, price differences have usually collapsed into
three real variables: what the builder pays for labor and material, what the
builder charges to manage the work, and how much risk the builder priced rather
than deferred.

The third one is the one that decides how the project feels. A bid that priced
risk shows up as a slightly higher number and a stable contract. A bid that
deferred risk shows up as an attractive number and a stream of adjustments that
arrive when you have the least leverage, because the walls are open and the
crew is on site.

The most useful protection is to involve a builder during design rather than at
the end of it. A constructability review and a real budget before the drawings
are final removes most of the ambiguity that produces bid spread in the first
place. That preconstruction sequence is a core part of how
[residential development](/residential-development) work should be run, and it
converts bidding from a guessing exercise into a comparison of firms.

## Frequently asked questions

### Should I automatically reject the lowest number?

No, but you should find out why it is lowest before you accept it. A low number can reflect genuine efficiency, available crew capacity, or a subcontractor who wants the job. It can also reflect missing scope, thin general conditions or an allowance nobody can buy at. Ask the question directly and read the exclusions page before drawing a conclusion.

### What is the difference between an allowance and a contract amount?

An allowance is a placeholder for work or material that has not been selected yet, carried at an assumed value so the contract has a number in it. A contract amount is priced against something specific. Every allowance is an open item, and the difference between the allowance and what you actually choose becomes an adjustment to the contract price.

### How complete do drawings need to be before bidding?

Complete enough that a bidder does not have to guess. That means finish schedules, a specification for major systems, structural drawings, and details for anything non-standard. Bidding on schematic drawings guarantees a spread, because every bidder fills the gaps with different assumptions and none of those assumptions are visible in the final number.

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Source: https://www.tricanagroup.com/insights/why-do-construction-bids-for-the-same-project-vary-so-much
Topic: Cost & Budgeting
Author: Hagop Sargisian, Tricana Group
Area served: Los Angeles County, CA; Orange County, CA
Published: 2026-06-18T09:00:00-07:00