What Warranties Should Your ADU Builder Provide?

Why ADU Builder Warranties Matter

Building an Accessory Dwelling Unit (ADU) is a significant investment, typically ranging from $150,000 to $400,000 or more in California. Like any major construction project, things can go wrong after the builder has left the job site. Cracks may appear in the foundation, plumbing may leak behind walls, or roofing may fail prematurely. This is where builder warranties become essential.

A comprehensive warranty from your ADU builder protects you against defects in materials and workmanship, ensuring that problems discovered after construction are repaired at the builder's expense rather than yours. Unfortunately, many homeowners do not understand what warranties they should expect, what is covered versus excluded, and how to enforce warranty claims when issues arise.

In this detailed guide, we will examine every type of warranty your ADU builder should provide, California-specific warranty laws and protections, what to look for in your contract, how to file warranty claims effectively, and how to protect yourself if your builder refuses to honor their obligations. Whether you are about to sign a contract or are experiencing post-construction issues, this guide will give you the knowledge you need to protect your investment.

Types of Warranties for ADU Construction

ADU builder warranties typically fall into several categories, each covering different aspects of the construction for different lengths of time. Understanding these categories is critical for knowing what protection you have.

1. Structural Warranty

The structural warranty covers the major structural components of your ADU, including the foundation, load-bearing walls, roof structure, floor framing, and support beams. Structural failures are the most serious and expensive problems that can occur in a building, so this warranty provides the longest coverage period.

Component	Typical Coverage	Industry Standard
Foundation	10 years	Covers cracking, settling, and structural failure
Load-Bearing Walls	10 years	Covers structural integrity issues
Roof Structure	10 years	Framing and trusses, not roofing materials
Floor Framing	10 years	Joists, beams, and subfloor structure

In California, the Right to Repair Act (SB 800) provides a statutory framework for construction defect claims on new residential construction. Under SB 800, structural defects have a statute of limitations of 10 years from the date of substantial completion. This means even if your builder's written warranty is shorter, California law may provide additional protection.

2. Systems Warranty (Mechanical, Electrical, Plumbing)

The systems warranty covers the mechanical, electrical, and plumbing (MEP) systems in your ADU. These systems are critical to habitability and can be expensive to repair or replace.

System	Typical Coverage	Common Issues
Plumbing	2 to 4 years	Leaks, pipe failures, improper drainage
Electrical	2 to 4 years	Faulty wiring, tripping breakers, code violations
HVAC	2 to 5 years	Refrigerant leaks, improper sizing, duct failures
Water Heater	1 to 2 years (labor) + manufacturer warranty	Leaks, thermostat failures, sediment buildup

Under SB 800, systems defects have shorter limitation periods: plumbing and sewer issues must be reported within 4 years, electrical defects within 4 years, and HVAC defects within 4 years of substantial completion.

3. Workmanship Warranty

The workmanship warranty covers the quality of the builder's labor and installation practices. This is the broadest category and typically covers items like drywall finishing, paint application, tile installation, cabinet installation, door and window fitting, and trim work.

Industry standard for workmanship warranties is 1 to 2 years from the date of completion. This covers defects that become apparent during normal use, such as:

• Drywall cracks from improper taping or mudding
• Paint peeling or bubbling due to poor surface preparation
• Tile cracking from improper substrate preparation
• Doors or windows that stick, bind, or fail to seal properly
• Cabinet doors that do not align or close properly
• Trim gaps, nail pops, or finish defects
• Flooring issues such as squeaking, buckling, or uneven surfaces

4. Manufacturer Warranties

In addition to the builder's warranties, many individual products used in your ADU come with their own manufacturer warranties. Your builder should provide you with all manufacturer warranty documentation at the time of project completion.

Product	Typical Manufacturer Warranty
Roofing Materials	20 to 50 years (material only)
Windows	10 to 20 years (glass seal), lifetime (frame)
HVAC Equipment	5 to 10 years (parts), 1 year (labor)
Appliances	1 to 5 years
Water Heater	6 to 12 years
Plumbing Fixtures	Limited lifetime

5. Implied Warranties Under California Law

California law provides additional warranty protections beyond whatever is written in your contract. These are known as implied warranties and cannot be waived or disclaimed by the builder.

• Implied Warranty of Merchantability: The ADU must be suitable for its intended purpose as a dwelling
• Implied Warranty of Habitability: The ADU must meet all building codes and be fit for human habitation
• Implied Warranty of Good Workmanship: The construction must meet generally accepted standards of quality

Under California Civil Code Section 896 (SB 800), these implied warranties provide a minimum floor of protection that applies to all new residential construction, including ADUs.

California's Right to Repair Act (SB 800) and Your ADU

SB 800, also known as the Right to Repair Act, is a California statute that establishes specific standards for new residential construction and provides a mandatory dispute resolution process before homeowners can file construction defect lawsuits. This law applies to all new residential construction completed after January 1, 2003, including ADUs.

SB 800 Limitation Periods

Defect Type	Limitation Period
Structural defects	10 years
Water intrusion / weatherproofing	10 years
Plumbing and sewer	4 years
Electrical systems	4 years
Soil and grading	4 years
Fire protection	4 years
Other defects (paint, finishes, etc.)	1 to 2 years

SB 800 Dispute Resolution Process

Before you can file a lawsuit against your ADU builder for construction defects, SB 800 requires you to follow a specific process:

1. Written notice: Send a written notice to the builder describing all defects
2. Builder inspection: The builder has 14 days to acknowledge receipt and up to 75 days to inspect
3. Repair offer: The builder must make a written offer to repair within a specified timeframe
4. Homeowner response: You can accept, reject, or negotiate the repair offer
5. Litigation: If no resolution is reached, you may file a lawsuit

What to Look for in Your Builder's Warranty Agreement

Before signing a contract with your ADU builder, carefully review the warranty provisions. Here are the key elements to look for:

Coverage Periods

Ensure the warranty clearly states coverage periods for each category: structural (10 years minimum), systems (2 to 4 years), and workmanship (1 to 2 years). Be wary of builders who offer blanket "1-year warranties" without distinguishing between categories.

Exclusions and Limitations

Every warranty has exclusions. Common exclusions include normal wear and tear, homeowner modifications, lack of maintenance, and acts of nature. Make sure the exclusions are reasonable and clearly defined.

Transferability

If you plan to sell the property or the ADU, check whether the warranty transfers to the new owner. Many builder warranties are transferable, but some have restrictions or fees associated with the transfer.

Dispute Resolution

Review how warranty disputes are handled. Some contracts require mandatory arbitration, which can limit your legal options. Others allow for mediation first, which is generally more homeowner-friendly.

Response Times

The warranty should specify how quickly the builder must respond to warranty claims and how long they have to complete repairs. A reasonable response time is 14 to 30 days for non-emergency issues and 24 to 48 hours for emergencies.

Red Flags in Builder Warranties

Watch out for these warning signs when reviewing your builder's warranty:

• No written warranty at all: Any reputable builder should provide a written warranty. Verbal promises are difficult to enforce.
• Extremely short coverage periods: A builder offering only a 90-day or 6-month warranty is not providing adequate protection.
• Excessive exclusions: If the warranty excludes so many items that meaningful coverage is limited, negotiate for better terms.
• Mandatory binding arbitration: While common, binding arbitration can favor builders over homeowners. Negotiate for mediation as a first step.
• No specification of response times: Without response time requirements, a builder could delay repairs indefinitely.
• Waiver of implied warranties: Under California law, implied warranties cannot be waived for new residential construction. If a contract attempts to waive them, that provision may be unenforceable.

How to File a Warranty Claim

If you discover a defect in your ADU, follow these steps to file an effective warranty claim:

Step 1: Document Everything

Take detailed photographs and videos of the defect. Note the date you first noticed it, any conditions that may have contributed, and the location within the ADU. Keep a written log of all communications with your builder.

Step 2: Submit Written Notice

Send a formal written notice to your builder describing the defect. Use certified mail or email with delivery confirmation so you have proof of delivery. Reference your warranty agreement and the specific provision that covers the defect.

Step 3: Allow Inspection

Give your builder a reasonable opportunity to inspect the defect. Under SB 800, builders have up to 75 days to inspect after acknowledging your claim. Be present during the inspection and take your own notes.

Step 4: Evaluate the Repair Offer

If the builder offers repairs, evaluate whether the proposed solution adequately addresses the problem. You have the right to negotiate or request alternative solutions. If the builder denies the claim, ask for a written explanation.

Step 5: Escalate if Necessary

If the builder refuses to honor the warranty, you have several options:

• File a complaint with the Contractors State License Board (CSLB)
• Pursue mediation through a neutral third party
• Consult a construction defect attorney
• File a lawsuit (after completing SB 800 procedures)

Third-Party Warranty Programs

In addition to builder-provided warranties, you may want to consider third-party warranty programs that provide independent coverage and dispute resolution. Major third-party warranty providers include:

• 2-10 Home Buyers Warranty: Covers structural defects for 10 years, with additional coverage for systems and appliances
• Quality Builders Warranty (QBW): Provides comprehensive 1/2/10 coverage (1 year workmanship, 2 years systems, 10 years structural)
• StrucSure Home Warranty: Offers customizable coverage plans with independent claims processing

Third-party warranties typically cost $300 to $1,500 and provide an additional layer of protection beyond the builder's own warranty. They are especially valuable if you have concerns about the builder's long-term financial stability or willingness to honor claims.

Frequently Asked Questions

How long should an ADU warranty last?

A comprehensive ADU warranty should include 10 years for structural components, 2 to 4 years for mechanical, electrical, and plumbing systems, and 1 to 2 years for workmanship and finishes. California law (SB 800) provides minimum protection periods even if the builder's written warranty is shorter.

What is the difference between a builder warranty and a manufacturer warranty?

A builder warranty covers the quality of construction work and installation, while a manufacturer warranty covers defects in the products themselves (appliances, roofing materials, windows, etc.). Both should be provided, and they work together to protect different aspects of your ADU.

Can a builder refuse to honor their warranty?

A builder can dispute a claim if they believe the defect falls outside warranty coverage (such as normal wear and tear or homeowner-caused damage). However, they cannot refuse to honor valid warranty claims. If they do, you can file a complaint with the CSLB or pursue legal action.

What if my ADU builder goes out of business?

If your builder goes out of business, their warranty effectively becomes unenforceable. This is why third-party warranty programs and the CSLB bond are important safeguards. California requires licensed contractors to maintain a $25,000 surety bond, which can provide limited compensation for unresolved claims.

Should I get a home inspection before the warranty expires?

Absolutely. We strongly recommend having a professional home inspection performed 30 to 60 days before each warranty period expires. This allows you to identify and report any defects while they are still covered. The cost of an inspection ($300 to $600) is a small price to pay for the peace of mind and potential savings.

Does a warranty transfer to a new owner if I sell my property?

Many builder warranties are transferable, but check your specific warranty agreement for transfer requirements. Some warranties require notification to the builder, and some charge a transfer fee. Manufacturer warranties are generally tied to the product rather than the owner and transfer automatically.

Frequently Asked Questions About ADU Builder Warranties

What should I do if my ADU builder refuses to honor a warranty claim?

If your ADU builder refuses to honor a legitimate warranty claim, start by putting your complaint in writing with photos and a detailed description of the defect. Reference the specific warranty terms from your contract that cover the issue. Send the letter via certified mail so you have proof of delivery. If the builder still does not respond, file a complaint with the California Contractors State License Board (CSLB), which oversees licensed contractors and can investigate disputes. You can also contact your local Better Business Bureau or consider mediation through a consumer protection organization. As a last resort, California homeowners can pursue legal action in small claims court for claims up to $10,000 or through a construction attorney for larger disputes. Documenting everything from the start, including all communications, photos, and receipts, strengthens your position significantly.

How long do structural warranties typically last on California ADUs?

Structural warranties on California ADUs typically last 10 years under California Civil Code Section 896, which provides statutory protections for new residential construction. This covers major structural components including the foundation, load-bearing walls, roof framing, and other elements that affect the structural integrity of your ADU. Beyond the statutory protection, many reputable builders offer their own structural warranties that match or exceed this 10-year period. Workmanship warranties on non-structural items like finishes, fixtures, and appliances usually last one to two years. Always ask your builder to provide warranty terms in writing before signing a construction contract so you know exactly what is covered and for how long.

Are appliance warranties separate from the builder's warranty?

Yes. Appliance warranties are provided by the appliance manufacturers, not by your ADU builder. Most major appliances come with a one-year manufacturer warranty that covers defects in materials and workmanship. Your builder is responsible for ensuring appliances are properly installed and functioning at the time of handover, but ongoing appliance issues fall under the manufacturer's warranty. Keep all appliance manuals, receipts, and warranty registration cards in a safe place. Consider purchasing extended warranties on high-value appliances like HVAC systems, water heaters, and kitchen appliances, as these items are expensive to repair or replace. Your builder should provide you with a complete list of all installed appliances, their model numbers, and warranty information at project completion.