What to compare at a glance
CSLB recommends obtaining at least three written bids and comparing them using identical plans, specifications and scope of work. That is the starting point, not the whole comparison. ADU prices can still differ because bidders make different assumptions about the existing property, utility routes, finish selections and services outside construction.
| Check | What should match or be explained |
|---|---|
| Drawing basis | Same plan set, issue date and revision numbers. |
| Construction scope | Same building area, rooms, systems, finish expectations and exterior work. |
| Existing site | Access, demolition, grading, foundation assumptions and protection of the main house. |
| Utilities | Trenching, connections, service or panel upgrades, meters and agency coordination. |
| Allowances | Amount, quantity, assumed product level, included tax, delivery, labor and markup. |
| Exclusions | Work or costs the Owner must separately arrange or budget. |
| Schedule | What starts the duration, owner dependencies, long-lead items and stated exclusions. |
| Proposal version | One dated proposal containing all accepted clarifications. |
Five things that change the comparison
- The drawings are not the same. A price based on an early floor plan is not directly comparable with a price based on a coordinated permit set. Record the exact files each bidder used.
- “Utilities included” means different things. It may refer only to work inside the ADU, or it may include trenching and connections back to existing services. Ask where each included utility scope begins and ends.
- One bidder investigated the property. A proposal that reflects a site visit, available records or completed investigations may look higher than a proposal that leaves those conditions unresolved.
- Finish selections sit at different levels. A low cabinet, flooring or fixture allowance transfers a predictable future cost to the Owner. Compare the assumed product and quantity, not the allowance number alone.
- Design, permits and agency fees are handled differently. Separate the Contractor’s construction price from design services, engineering, permit processing, agency fees and utility-provider charges.
How to evaluate three bids
Keep every original proposal. Build a separate comparison sheet that records the bidder’s own answer for each important item. Do not rewrite a vague statement as “included” just because you expect the work to be necessary.
| Status | Meaning | Owner action |
|---|---|---|
| Included | The proposal identifies the work and any limits. | Confirm that the description matches the intended result. |
| Allowance | An amount is included for a defined item that will be reconciled later. | Check the assumed product, quantity and adjustment method. |
| Excluded | The bidder is not providing or pricing the item. | Add a separate budget or assign responsibility. |
| Unresolved | The condition or scope has not been determined. | Record what investigation or decision will resolve it. |
Once the important rows are complete, calculate an adjusted comparison only for additional costs supported by a quote or a clearly labeled planning estimate. Never turn an unknown into zero simply to produce a total.
Understand what kind of price you received
A square-foot rate describes a price. Lump sum and cost-plus describe how the amount owed may be calculated. A bidder can use a square-foot rate for an early estimate and later offer a lump-sum proposal for defined work.
| Price description | Question to answer |
|---|---|
| Budget or feasibility estimate | Which scope and unknowns prevent this from being a contractual offer? |
| Price per square foot | Which floor area is counted and which costs sit outside the rate? |
| Lump sum | Which documents define the work, and which provisions may adjust the total? |
| Cost-plus | Which costs qualify, what records are provided and how is the fee calculated? |
A label such as “fixed price” does not explain allowances, Owner changes, concealed conditions or other adjustment provisions. Those terms belong in the proposed agreement. CSLB advises putting important promises in writing and understanding the contract before signing.
Common warning signs
- The total is substantially lower, but the proposal does not explain why.
- The bid does not identify the drawing set or revision used.
- Necessary-looking work is absent from both inclusions and exclusions.
- Large allowances have no quantity or product basis.
- Site work and utilities are described with one broad word such as “included.”
- Oral clarifications are not incorporated into a revised written proposal.
- The payment request is being discussed before the scope and agreement are settled.
A warning sign is a reason to ask for clarification, not proof of wrongdoing. CSLB specifically cautions homeowners not to accept the lowest bid automatically and notes that a substantially lower bid may reflect a mistake or omitted work.
When the bids are not ready to compare
Pause the price comparison if the project is still described differently to each bidder, the design has changed between visits, or major site and utility questions remain unassigned. You may still use the proposals for early budgeting, but do not present the totals as equivalent offers.
The bids are also not ready if you cannot tell which company would sign the construction contract, which services are provided by separate designers or consultants, or which Owner decisions are required before the price can be relied on.
This comparison cannot establish workmanship quality, future performance or the final project cost. Combine it with license research, relevant-project evidence, references and contract review.
What to do next
- Confirm one current drawing and scope package for all bidders.
- Complete the ADU quote-basis checklist.
- Send the same short clarification list to each bidder.
- Keep revised proposals dated and separate.
- Research the company identity and relevant experience before selecting a finalist.
- Move the accepted scope, allowances, exclusions and promises into the written agreement.
Questions, answered
Should I choose the lowest ADU bid?
Not until you confirm that the bids use the same drawings, specifications and scope. A lower total may omit site work, utilities, permit coordination, finish allowances or other work included by another bidder.
Link to this answerMust every ADU bid use the same format?
No. Keep each original proposal and use a separate comparison table for the project assumptions that matter. Ask each bidder to clarify missing items in writing.
Link to this answerWhat if a site condition cannot be priced yet?
Label it unresolved rather than treating it as included or assigning it a zero cost. Record what investigation is needed, who will obtain it and how the result may affect price or schedule.
Link to this answerOfficial sources
Official references checked on . Legal requirements, agency guidance and PrepareToBuild.info recommendations are not presented as the same thing.
| Source | Used for |
|---|---|
| CSLB: Finding the right licensed Contractor | Three written bids; identical plans, specifications and scope; lowest-bid caution; license and reference checks. |
| CSLB: Home improvement contracts | Written scope, materials, payment schedule, permits, completion date and written changes. |
Prepared for PrepareToBuild.info as an editorial draft, assisted by AI. Not yet reviewed by a licensed construction or legal professional. Examples and comparison categories are educational tools, not bids, legal terms or guarantees. Confirm requirements with the responsible agency and obtain qualified advice for the property and proposed agreement.