Mechanics liens in California: a guide for ADU owners

How a mechanics lien works in California

A mechanics lien is a hold against your property, recorded with the county recorder, by someone who improved it and wasn't paid. The Contractors State License Board explains the trap: if your contractor doesn't pay a subcontractor, laborer or material supplier, you're ultimately responsible, even if you've already paid the contractor. That can mean paying twice for the same work. An unpaid lien can lead to foreclosure, and a recorded one clouds your title, which can block a loan, a refinance or a sale.

An ADU raises the stakes. It's a six-figure job with a foundation crew, framers, electricians, plumbers, roofers and a dozen suppliers, most of whom you'll never meet. (See what an ADU costs in San Diego for the size of the numbers involved.) Every one of them who has a right to be paid has a potential lien on your lot.

The rules live in the Civil Code, starting at section 8000. The amount of a lien is capped: it's the lower of the reasonable value of the claimant's work or the price they agreed to. A supplier can't lien you for more than the lumber was worth.

Who can lien your ADU

Source: Civil Code section 8200. Anyone who contracts directly with you, like your general contractor, gives preliminary notice only to a construction lender. Subcontractors and suppliers must give it to you. If you're paying with a construction loan, the lender is on every notice too; see our guide to ADU financing for how construction loans disburse.

Preliminary notice

A preliminary notice is the letter a subcontractor or supplier sends to say “I'm working on your property.” It's a condition of a valid lien: without one, most claimants can't record a lien at all.

The 20-day rule

The notice is due no later than 20 days after the claimant first furnishes work. A late notice is allowed, but it only protects work done in the 20 days before it was served and everything after. A supplier who delivered your framing package two months ago and sends a notice today can't lien for that delivery.

What's in it

The notice must include a description of the work, an estimate of its total price and a boldface “NOTICE TO PROPERTY OWNER” that begins, “EVEN THOUGH YOU HAVE PAID YOUR CONTRACTOR IN FULL,” and warns that you could lose part or all of your property to foreclosure.

Mechanics lien deadlines

California's lien deadlines run from the date the work of improvement is complete. Under Civil Code section 8180, completion happens on the first of: actual completion; you occupying or using the ADU while work has stopped; work stopping for 60 days in a row; or you recording a notice of cessation after work has stopped for 30 days in a row.

Sources: section 8182, section 8412, section 8414 and section 8460. The 90-day suit deadline can be extended only if you and the claimant agree to extend credit and record notice of it, and even then the suit must be filed within one year after completion.

A recorded lien must also be mailed to you, with a notice in boldface telling you the claimant must sue within 90 days. If the claimant doesn't serve you as required, the lien is unenforceable.

Lien release forms

A lien release (the statute calls it a “waiver and release”) is a signed statement from a contractor, sub or supplier giving up lien rights for work they've been paid for. California has four statutory forms, and a release only protects you if it's in substantially the form the law provides and signed by the claimant. Ask for the statutory form by name; a homemade “receipt” may not hold up.

The progress forms leave out retention, unpaid extras and earlier unpaid payments, so read the exceptions box. The unconditional forms carry a warning to the claimant that the document is enforceable “even if you have not been paid,” which is exactly why it protects you.

You also have leverage. Under the home improvement law, after any payment your contractor must, if you ask, give you a full and unconditional release from potential lien claimants for the work you've paid for, and you “may withhold all further payments until these releases are furnished.”

How to avoid a mechanics lien

Most of the work happens before you sign. The licensing board's prevention checklist, adapted to an ADU build:

• Hire a licensed contractor with a clean payment history. Check a contractor's license, make sure their subcontractors are licensed, and look for lawsuits by subs or suppliers at the local courthouse.
• Get the subcontractor list. Since January 1, 2026, a home improvement contractor must give you each subcontractor's name, contact information, license number and classification on request.
• Write payments to phases. Tie each payment to finished work, never ahead of it. Our ADU contract checklist covers the payment schedule clause by clause.
• Keep a lien log. List every preliminary notice: company, trade, estimated price, date received.
• Trade releases for money. Conditional release from your contractor, and from every sub or supplier on your log who's being paid from that draw, before each payment. Unconditional releases after.
• Use joint checks for big suppliers. A check payable to both your contractor and, say, the lumber yard means the supplier has to endorse it. Compare the bill against the schedule first.
• Hold the last payment for final releases. The board's sample ADU schedule holds 3% for final inspection and 2% for keys after the punch list. Pair those with final releases.
• Record a notice of completion once the ADU passes final inspection. See below.

Your contract must already carry a “Mechanics Lien Warning” under the home improvement contract law; it opens, “Anyone who helps improve your property, but who is not paid, may record what is called a mechanics lien on your property.” The same law gives you the right to require a performance and payment bond, which shifts the risk of an unpaid sub onto a surety. Our guide on how to hire an ADU contractor covers the rest of the vetting.

Notice of completion

A notice of completion is a short form you sign, verify and record with the county recorder. Recorded on or within 15 days after the date of completion, it cuts the time to record a lien from 90 days to 60 for your contractor and to 30 for everyone else. A notice that doesn't meet the statute isn't effective, and if the completion date on it is wrong, it still works only if the true date was no more than 15 days before you recorded. For an ADU, the natural trigger is the city's final inspection; our ADU inspection checklist covers that step.

Do you have to mail copies?

Normally the owner must send a copy, within 10 days of recording, to the direct contractor and everyone who sent a preliminary notice. Skip it and the shorter deadline doesn't apply to that person. But an owner who lives on the property as a personal residence, with four or fewer units, is exempt. A main house plus an ADU fits. If you don't live there (say you rent out both units), mail the copies.

When the job stalls

If your contractor walks off and nothing happens for 30 days in a row, you can record a notice of cessation, which counts as completion for lien deadlines and starts the same short clocks. That's relevant if your builder fails mid-project, a risk our guide to ADU builder red flags covers.

If a lien is recorded on your home

• Check the dates. Was a preliminary notice served within the 20-day window? Was the lien recorded in time, and was it mailed to you? A lien that misses a step may be unenforceable.
• Watch the 90-day clock. If the claimant hasn't sued within 90 days of recording, the lien expires and is unenforceable. It still sits on your title until it's released.
• Demand a release, then petition. You can ask the court for a release order once that deadline passes, after giving the claimant at least 10 days' written notice demanding a release. If you win, the court orders the property released, and the prevailing party gets reasonable attorney's fees.
• Bond around it. If you dispute the lien and need clean title now (to refinance or sell), you or your contractor can record a lien release bond for 125% of the claim, which releases the property and moves the fight to the bond.
• Hold the contractor to the contract. If you paid your contractor and they didn't pay the sub, you may have a claim against the contractor; ask a lawyer. You can withhold further payments until you get releases, and you can file a complaint with the licensing board.

Common questions