How to Compare ADU Contractor Bids: What Every Quote Should Include

California edition · Reviewed September 2, 2026. A practical comparison method for homeowners collecting bids for a conventional ADU. Local requirements, project documents and the eventual signed contract control the work.

A $265,000 ADU quote can represent a larger commitment than a $288,000 quote. The difference may be buried in utility exclusions, a small finish allowance or work the owner must purchase separately.

To compare ADU contractor bids, give every bidder the same documents, identify what each price includes, adjust only for documented differences, and keep unresolved costs visible. Then evaluate the contractor and contract terms alongside the adjusted price. A polished proposal is not evidence that all the necessary work is covered.

This guide walks through an illustrative three-bid comparison, a 16-part scope checklist and California-specific contract questions. If you are still creating your shortlist, start with how to find a good ADU contractor in California.

1. Give every contractor the same project to price

Before comparing numbers, send one bid package: the same drawings and revision date, engineering information available, finish schedule, known site constraints and list of owner-supplied items. Identify whether the plans are preliminary, submitted or approved. A conceptual estimate and a construction proposal based on approved plans answer different questions.

Ask all bidders to visit the property or explain what they have assumed without a visit. Record gate width, material storage, occupied-house access, demolition, trees to protect and where trenches might run. Do not assume the contractor has inspected underground conditions simply because they walked the yard.

Request a base price, itemized allowances, explicit exclusions, separately priced alternates, an anticipated schedule and a validity date. When one contractor asks a question that changes scope, send the answer to every bidder. Otherwise, the revised prices still describe different projects.

2. Put every scope item into one of four categories

“Utilities included” is too broad to classify confidently. Does it cover the trench on your lot, pipe and wire, connection labor, the existing home’s panel, pavement restoration and utility-company charges? Ask for the boundaries in writing.

3. Compare the same scope: a three-bid example

These are fictional teaching figures, not California market prices, actual quotes or a forecast. Assume three contractors priced the same detached ADU drawings. For this example, subsequent written clarifications establish the costs shown below. Each base bid already contains its stated finish allowance.

*The example assumes these additions include applicable tax, labor and markup, with no overlapping charges. A zero means this defined scope is already included, not that the work has no cost.

Bid A starts $23,000 below Bid B but ends $6,000 above it for the specified scope. That does not prove B is the best contractor. It shows that the initial price ranking was misleading. Quality, supervision, availability and contract terms remain separate decisions.

Do not add the full $20,000 finish budget to Bid A: its base already includes $12,000. Add only the $8,000 difference. If an allowance covers materials only, first establish installation, tax, delivery and markup so you are comparing the same package.

Now imagine the sewer connection has not been investigated. Every bid could change. Record “sewer condition unresolved,” identify the investigation needed and ask who will price the result. A planning range may help your budget, but it is not a confirmed contract price. A contingency is money you reserve; it does not transfer the contractor’s exclusions into their scope.

4. What every ADU quote should address

A contractor need not include every item in one contract. The goal is to identify where each item sits, who is responsible and how its cost will be established. Use this scope register when requesting revised bids.

5. California details that deserve their own line items

Energy compliance follows the applicable permit rules

The California Energy Commission says permit applications made on or after January 1, 2026 must comply with the 2025 Energy Code. Check your project’s applicable edition rather than assuming a newly received bid uses the right one. Ask who provides compliance documentation, required testing and the specified equipment. See the CEC’s 2025 Energy Code guidance.

Have the designer identify the ADU’s specific solar requirements and any applicable exceptions. Then ask each bidder to state the PV equipment, installation, electrical integration and approval scope included. “Title 24 included” is not a complete solar specification. The CEC’s ADU FAQs distinguish project circumstances; do not apply one detached-new-build assumption to every conversion.

Utility construction and utility-company work are different scopes

Separate the contractor’s on-site work from the service provider’s design, equipment, charges and scheduling. Ask who opens the utility application, follows up and supplies the required documents. PG&E describes a review process in which some projects need service or neighborhood-facility changes and others do not. Use PG&E’s residential project resources where it is your provider; obtain the equivalent guidance from your own utility elsewhere.

An electrical subcontractor’s panel price is not automatically the full cost of bringing service to the ADU. Request the assumed service arrangement, route and responsibility boundary. Treat an unconfirmed utility charge as unresolved, even when someone describes the bid as turnkey.

Fee relief does not make all agency charges disappear

Request separate lines for permit and plan-review charges, impact fees, school charges and utility connection or capacity charges where applicable. Have the relevant agency confirm the project’s treatment in writing. Use the current HCD ADU handbook and guidance to frame your questions. A generic “ADU fees waived” statement is not a project-specific fee breakdown. Our California ADU permit guide explains the broader approval process.

6. Compare the contract, payment schedule and change process

A bid summary does not replace a complete construction contract. Before signing, confirm that the selected proposal, scope clarifications and drawings are incorporated consistently, with a clear rule for resolving conflicting documents. Ask a California construction attorney to review terms that you do not understand, particularly for a new detached dwelling or an unusual procurement arrangement.

For work covered by California’s home-improvement-contract rules, CSLB states that the down payment is limited to the lesser of $1,000 or 10% of the contract price. Confirm which contract rules apply to your ADU; do not assume a new detached build and a conversion necessarily use identical paperwork. CSLB also calls for a written payment schedule and written, signed change orders before changed work. See CSLB’s contract guidance.

Ask the contractor to describe the work or delivered materials associated with each payment and the evidence you will receive. Establish how changes are priced, who approves them and how time changes are documented. An inspection milestone alone does not explain everything covered by a payment.

For a fixed-price contract, examine exceptions and allowances. For cost-plus work, ask which costs are reimbursable, how the contractor’s fee is calculated, whether subcontractor markups stack, what records you can review and whether any proposed ceiling has exceptions. A headline number is not a guaranteed maximum merely because it appears at the top of a proposal.

Plan lien documentation before the first progress payment

CSLB warns that paying the general contractor does not guarantee subcontractors and suppliers have been paid. Agree on a process for the appropriate progress and final releases, and identify whose releases are needed. Conditional and unconditional forms have different effects; use the official forms and obtain advice if a payment or release is disputed. The downloadable worksheet is not a lien waiver. See CSLB’s waiver and release forms.

Download the California bid checklist and record the written clarifications beside each bidder’s figures.

7. Send one useful clarification request

Please revise your proposal against the attached plan revision and scope register. For each item, identify included work, allowance, exclusion or unresolved condition. Show allowance amounts and adjustment rules; identify taxes, installation and markup; price the listed missing scope separately; and state the assumptions behind your schedule. Please also identify the documents that will become part of the contract and the validity date of the revised price.

Ask for a revised proposal or signed clarification, not just an encouraging phone call. If a contractor cannot price an unknown yet, ask for the investigation, responsible person and target date. An honest unresolved item can be more useful than an unsupported promise that everything is covered.

8. Make the selection in two passes

Do not average these into an invented score. If a material scope question or contractor-verification issue is unresolved, resolve it before choosing on price. Document why you selected the contractor, including any accepted exclusions and the budget you will need outside their contract.

Once selected, carry the same scope register into your kickoff meeting. Our ADU construction-process guide explains the inspections, decisions and handover records that follow permit approval.

Common questions about ADU bids

Should I choose the lowest bid?

Only after establishing comparable scope and checking the contractor and terms. A lower price may reflect efficiency, a different specification, less work or greater uncertainty. The proposal alone does not tell you which.

Is a cost-per-square-foot quote enough?

It can help frame an early discussion, but it does not identify fixed site costs or exclusions. Compare total defined project scope first. Two identical floor areas can have different access, utility and foundation requirements.

What does turnkey mean?

Whatever the signed scope actually defines. Ask whether design, fees, connections, appliances, testing, final approvals and site restoration are included. Do not treat the word itself as a list of deliverables.

What if my plans are not approved yet?

Use bids to test the budget, label the design assumptions and ask how revisions will be priced. Do not present an early estimate as equivalent to a proposal based on final construction documents.

Does the adjusted total predict the final bill?

No. It compares known scope at a point in time. Owner changes, unresolved site conditions and other contract provisions can still affect spending. Keep those exposures visible in a separate project budget.

Method: original illustrative comparison and editorial checklist; California requirements checked against the official resources linked above. No contractor quotes or market-price dataset were used. Photo: Lucas Kepner via Unsplash.