What Is a California 20-Day Preliminary Notice for ADU Projects?

Who Should Send a California 20-Day Preliminary Notice?

In California, subcontractors and material suppliers usually must meet preliminary notice rules. This applies if they do not have a direct contract with the current property owner. Meeting these rules protects their right to file a mechanics lien or bond claim. Direct contractors must also send a notice if the project involves a project lender or, in some cases, work for a public entity. Pure laborers—those providing only labor without furnishing materials—are exempt from this requirement.

You can deliver the notice by Overnight Delivery, certified mail, or other legal methods. It is important to follow official sources. You must meet the notice deadline to avoid missing filing dates.

As the Levelset Legal Team explains:

“Sending a California preliminary notice is an effective way to speed up payment on a construction project. A preliminary notice is an informational document typically sent to the property owner near the beginning of a construction project.”

Construction professionals send the notice quickly to all required parties. These parties include the original owner, general contractor, or lender. This helps protect their payment rights. It also helps avoid disputes that could cause contract lawsuits. They keep transparency from the start of an ADU project. The safest approach is to prepare the notice correctly, keep proof of delivery, and seek guidance from experienced construction litigation attorneys in any unusual situation.

If you don’t have a direct contract with the property owner, sending a preliminary notice protects your payment rights.

Importance of the 20-Day Preliminary Notice

Securing Lien Rights

Serving a California 20-Day Preliminary Notice within the first 20 days of providing labor or materials helps contractors, subcontractors, and suppliers keep their full mechanics lien rights for all work from that date on. If sent late, lien rights only cover work performed in the 20 days before the notice and any work thereafter (Source: Green Law Group). Filing promptly—whether in person, by mail, or with the county recorder’s office—is essential to avoid payment disputes that may require construction litigation lawyers or a skilled contract litigation attorney to resolve. Without preserved lien rights, recovering payment for earlier work can be much more difficult, especially if a lien on construction projects becomes necessary.

Streamlining Payment Processes

A preliminary notice creates transparency between current owners, general contractors, and all subcontractors or suppliers. By clearly identifying roles and payment expectations early, it supports smoother payment schedules, sometimes using joint checks to ensure funds reach the right parties. Many construction professionals use it as a best practice, even when the law does not require it. This helps prevent misunderstandings and lowers the risk of project debt or disputes that could lead to lawsuits over non-payment.

Protecting Business Relationships

Clearly identifying all parties and their potential lien rights early fosters trust between the property owner and contractors, whether for residential builds or ADU projects. This reduces the likelihood of unexpected lien releases being needed mid-project and avoids disputes that could escalate into breach of contract litigation. Being transparent from the start helps prevent problems with verbal contracts. It also supports following licensing rules and lets projects continue without legal or financial interruptions.

Serving notices early builds transparency, reduces disputes, and ensures full protection for all work completed from day one.

Legal Requirements for Sending a Preliminary Notice

Timing and Deadline

Under California law, a Preliminary 20-Day Notice must be sent within 20 days of first furnishing labor or materials to a project to preserve mechanics lien or bond claim rights. Sending the notice early—even before materials are delivered—is allowed and can help ensure compliance. The requirement is considered met when the notice is mailed; proof of mailing is sufficient to meet the deadline (Source: Levelset).

Essential Information to Include

To be valid, a preliminary notice must include:

• Name and address of the property owner
• Name and address of the direct (prime) contractor
• Name and address of the construction lender (if applicable)
• Description of the work or materials provided
• Claimant’s contact details

Common Mistakes to Avoid

Missing required details—especially the lender’s contact information—can invalidate the notice. Inconsistent sending practices across projects can also jeopardize lien rights.

Owner action guidance from the statutory notice:

You may want to protect yourself by asking your contractor to get a signed release from the person or company that gave you this notice before you pay your contractor. You can also use any other method that fits the situation. (Source: Sacramento County Public Law Library)

CSLB caution:

“Be careful: paying your contractor (and/or getting a release from your contractor) does not guarantee that other claimants, like subcontractors and suppliers, are paid. A claimant is a person who, if not paid, can file a lien on your property.” (Source: California State License Board)

Include every required detail—owner, contractor, lender, and scope—to keep your lien rights intact; omissions can void protections.

Process of Sending a Preliminary Notice

Choosing the Right Delivery Method

In California, the most reliable way to send a Preliminary 20-Day Notice is via certified mail through the United States Postal Service. This method costs under $5 and provides a tracking number, ensuring proof of when the notice was sent and received—an important safeguard if a lien on construction projects or other disputes arise later (Source: Levelset).

While personal delivery or a statement in person is technically allowed, it is not recommended because proving delivery can be difficult if challenged. Certified or registered mail gives the legal proof needed for lien rights. In some counties, like Orange County, this documentation may be part of the official record. The county clerk-recorder or recorder’s office keeps these records.

Documenting Proof of Delivery

Under California law, a preliminary notice is considered effective upon sending, not upon receipt. If the notice is returned as “Rejected” or “Unclaimed,” keep detailed records of your delivery attempts. Include mailing receipts, tracking logs, and any related legal forms or sample form copies (Source: Sacramento County Public Law Library).

Keeping this documentation not only ensures compliance with lien laws but also strengthens your position in case of a type of lawsuit over payment or if you must return through litigation to recover funds. Properly documenting proof of delivery is a best practice for protecting lien rights and supporting a strong legal standing in the event of a payment dispute.

Use certified mail with tracking to ensure you have verifiable proof when sending a Preliminary 20-Day Notice.

Differences Between Private and Public Projects

Preliminary 20-Day Notice Requirements for Private California Construction Projects

For private construction projects in California, subcontractors, material suppliers, and equipment lessors must send a Preliminary 20-Day Notice. They send it to the current property owner, the general contractor, and any construction lender involved. This requirement applies whether the project is residential or commercial (Source: Lloyd Winter).

Serving the notice ensures all parties are aware of the sender’s involvement, preserves mechanics lien rights, and helps prevent lien on construction projects if payment issues occur (Source: Levelset). In some cases, filing with the county recorder’s office may be an additional safeguard, especially if there is a risk of materials for breach or a standard breach of contract.

Preliminary 20-Day Notice Rules for Public Works Projects

For public works projects, subcontractors and suppliers must also serve a Preliminary 20-Day Notice to secure their right to make a bond claim if unpaid. General contractors, however, are typically exempt from sending the notice to themselves because they cannot claim against their own payment bond.

Many construction professionals and lawyers still recommend sending the notice. It creates clear communication. It helps ensure payments happen on time. It lowers the chance of disputes that could cause lawsuits about project payments (Source: Lloyd Winter, P.C.).

For private projects, lien rights depend on timely notices; for public works, bond claims follow similar rules but protect against different payment risks.

Consequences of Not Sending the Preliminary Notice

Forfeiture of Lien Rights

If a Preliminary 20-Day Notice is not served within the required timeframe, the claimant loses the right to file a mechanics lien for work performed before the notice was sent. (Source: CNS Lien) In California, lien enforcement deadlines are strict:

• 90 days after project completion if no Notice of Completion is recorded.
• 60 days for general contractors or 30 days for subcontractors if a Notice of Completion is filed (Lloyd Winter, P.C.).

Missing these deadlines or failing to send the notice at all removes a critical layer of payment protection, leaving contractors, subcontractors, and suppliers without legal leverage to secure unpaid funds.

Impact on Payment Timing

A late preliminary notice limits recovery to the value of labor or materials provided during the 20 days before the notice was sent and any work afterward (Levelset). This reduced coverage can result in significant unpaid balances for earlier work, particularly on multi-phase projects such as ADU builds. Serving the notice promptly helps maintain full payment rights and avoids costly gaps in protection.

Missing the 20-day deadline can limit your recovery rights; always send notices promptly to avoid costly payment gaps.

Best Practices for Managing Preliminary Notices

Record-Keeping and Documentation

Maintaining thorough records is essential for preserving mechanics lien rights in California. Keep delivery receipts, certified mail tracking numbers, and mailing logs for every Preliminary 20-Day Notice you send. If a notice is returned as “Rejected” or “Unclaimed,” retain all proof of your attempt to serve it, including postal documentation and any related correspondence (Source: Sacramento County Public Law Library). This documentation not only proves compliance with legal requirements but also strengthens your position if you need to enforce a lien later.

Keeping Track of Deadlines

Lien and notice timelines are strict. You should set calendar reminders for the 20-day preliminary notice deadline. This deadline starts from the date you first provide labor or materials. You should also set reminders for the mechanics lien deadlines. These deadlines are 90, 60, or 30 days depending on the situation. These reminders help ensure that no critical filing window is missed, which could result in losing payment rights. Using a project management tool or dedicated lien tracking software can further reduce the risk of oversight and keep all stakeholders informed.

Keep precise records of every Preliminary 20-Day Notice—blueprints, mailing receipts, and logs can be critical if a lien on construction projects is contested.

Lien Waivers for ADU Projects

What is a Lien Waiver?

A lien waiver is a legal document that confirms a contractor, subcontractor, or supplier has been paid for their work and, in exchange, waives their right to file a mechanics lien for that amount. As Purgula explains:

“The hallmark of a professional General Contractor is that he will provide the homeowner with a Mechanics Lien Waiver after payment… think of it as a ‘receipt’ that protects the homeowner.”

In the context of ADU construction, lien waivers protect property owners from future payment claims after they’ve paid for work or materials.

Types in California

California law recognizes four standardized lien waiver forms (California Civil Code §§ 8132–8138):

• Conditional Waiver on Progress Payment: Used before a progress payment clears.
• Unconditional Waiver on Progress Payment: Used after a progress payment has cleared.
• Conditional Waiver on Final Payment: Used before the final payment clears.
• Unconditional Waiver on Final Payment: Used after the final payment has cleared.

When to Use Each Type

• Conditional waivers are signed before payment is received or while it’s processing, making them effective only if payment clears.
• Unconditional waivers are signed after payment has been received and verified, permanently waiving lien rights for that payment.

Homeowner Protection Steps

Legal experts advise homeowners to be thorough when collecting lien waivers:

“Attorneys and reputable contractors suggest that homeowners get an unconditional lien waiver and release signed by the contractor and each material supplier, subcontractor and laborer. This cuts off the right of any of these parties to record a lien on the residence.” (Source: Los Angeles Times)

To protect against surprise liens:

• Require lien waivers from every party that has provided a Preliminary 20-Day Notice before releasing funds. (Source: Mastt)
• Use the statutory California waiver forms to ensure compliance and enforceability (Source: CSLB).

Collect lien waivers with each payment to safeguard against future lien claims.

How They Work Together in an ADU Project

At the start of an ADU project, contractors, subcontractors, and suppliers send Preliminary 20-Day Notices. They inform the property owner, general contractor, and lender if there is one about their involvement. This step preserves their right to file a mechanics lien if payment is not received and can be further supported by documenting the filing through the county recorder’s office when appropriate. Securing lien rights early helps prevent disputes that could escalate into a type of lawsuit over unpaid work.

Lien Waivers During and After Payment: As payments are made during the project, the property owner or general contractor should collect signed lien waivers from every party who has been paid. This process ensures that no one can later place a lien on construction projects for work already compensated and helps verify that all parties maintain their license status in good standing. Proper documentation of waivers and timely preliminary notices creates a clear and enforceable payment record. (Sources: Investopedia; Buildertrend).

Using preliminary notices and lien waivers together protects all parties:

• Homeowners avoid surprise liens.
• Contractors and suppliers have a documented path to payment.
• The project stays on track with fewer payment disputes.

Summary Table

Using California 20-Day Notices and Lien Waivers for ADU Projects

Understanding and correctly using California 20-Day Preliminary Notices and Lien Waivers is essential for a smooth, dispute-free ADU project. Preliminary notices protect contractors’ and suppliers’ rights to be paid, while lien waivers safeguard homeowners from future lien claims after payment. When used together—sending notices at the project’s start and collecting waivers with each payment—they create transparency, reduce legal risk, and foster trust between all parties. By following state requirements, keeping accurate records, and meeting deadlines, San Diego homeowners can confidently build their ADUs while protecting both their property and their investment.

Combine preliminary notices and lien waivers to reduce payment disputes and maintain project trust.