How to write a contractor workmanship warranty

Every contractor eventually gets that callback. The job was done right — or so you thought — and now a customer wants you back on-site. Whether you handle that visit as warranty work or a billable service call comes down to one thing: whether you wrote down what your contractor workmanship warranty covers before you ever cashed their check. A clear written warranty protects you from doing unlimited free work while still standing behind your craft. This post covers what to include, how long to offer by trade, what to exclude, and how to price the risk so callbacks don't eat your margin.

You already have a warranty, whether you wrote one or not

Before writing a single word, understand what you're working with: an implied warranty of good workmanship exists in your contracts with customers in every U.S. state, whether or not you mention it. As Levelset explains, the implied warranty means your work must be performed in a "good and workmanlike manner" — at the standard of care a skilled tradesperson would exercise. Courts apply this even when it's not spelled out in your paperwork.

That implied warranty is your floor. A written warranty doesn't add new liability — it defines and limits the liability you already have. Without a written warranty, your customer (or a court) decides what's covered and for how long. With one, you decide.

You also need to be clear on what a workmanship warranty is not. It covers the quality of your labor and installation. It does not cover product defects in the equipment or materials you installed — those fall under the manufacturer's warranty. If a heat pump fails due to a compressor defect two years after you installed it, that's a manufacturer's problem, not yours. Your written warranty needs to say so explicitly.

How long to offer by trade

The National Association of Home Builders (NAHB) popularized the "1-2-10" warranty structure in residential construction: 1 year on workmanship and materials, 2 years on mechanical systems (plumbing, HVAC, electrical), and 10 years on major structural defects. The full framework is detailed in their Beyond Warranty resource.

The structural tier doesn't apply to most service contractors. But the first two tiers translate directly to trade service businesses:

These are starting points, not ceilings. In competitive markets some contractors offer two-year warranties on routine service calls to stand out from the field. That's a business call. What you should never offer is an open-ended warranty with language like "satisfaction guaranteed for life" — courts have found those phrases to create indefinite repair obligations.

One detail that matters more than most contractors realize: start your warranty clock at final payment, not at the installation date. If a job takes three weeks to complete and the customer delays sign-off for another three months, a warranty starting at installation effectively gives them 15 months of coverage on a 12-month policy. Lock it to final payment accepted.

What to put in your contractor workmanship warranty

You don't need a five-page legal document. A clear paragraph added to your estimate or contract handles most residential trade work. Cover these six elements:

1. What's covered. Name the specific work: "Defects in workmanship on the installation of the 3-ton Carrier AC unit and associated refrigerant lines and electrical connections at [address]." Don't write "all work performed" — specificity limits your exposure.

2. Duration and start date. "This warranty is valid for [X] year(s) from the date of final payment received."

3. How to submit a claim. "Customer must notify [your company] in writing — email, text, or letter — within 5 business days of discovering the defect." In writing means there's a record. A vague phone call three months later isn't a warranty claim you're obligated to honor on anyone else's schedule.

4. Your remedy. "Contractor's sole obligation under this warranty is to repair or replace the defective workmanship at no cost to the customer. Cash refunds are not available under this warranty." Without this clause, a customer can argue that a defect entitles them to a full refund of the job price.

5. Exclusions. (List these separately — they earn their own section, covered below.)

6. What voids coverage. "This warranty is void if covered work has been altered, repaired, or modified by anyone other than [your company] without prior written consent." If another plumber re-works your manifold and causes a leak, that's not your warranty claim to absorb.

For jobs over a few thousand dollars, consider a short, standalone warranty document the customer signs at final payment rather than burying the terms in the estimate. It signals that you stand behind your work — on terms you wrote.

What to exclude from your warranty — and why it matters

Exclusions are the most valuable lines in any workmanship warranty. Without them, you absorb manufacturer failures, customer neglect, and damage caused by other trades.

• Manufacturer defects. The part failed, not your installation. Write explicitly: "This warranty does not cover defects in materials or equipment supplied by third-party manufacturers." Help the customer file a manufacturer warranty claim, but make clear it's not your obligation.

• Acts of God. Storm damage, flooding, lightning strike, earthquake, fire — none of these are workmanship defects.

• Improper maintenance. An HVAC system left running without filter changes for 18 months isn't your warranty problem. Include: "Damage resulting from failure to perform manufacturer-recommended maintenance is not covered." Handing the customer a printed maintenance checklist at job completion helps document that you told them.

• Customer modifications. If the customer installs a second thermostat, moves ductwork, or swaps plumbing fixtures after your work is done and something fails downstream, you're not on the hook.

• Normal wear and tear. Sealants dry, belts wear, rubber boots crack over time. These are maintenance items, not defects in your installation.

• Damage from other trades. On remodeling jobs, you share a job site. If a roofer's crew accidentally cuts your new refrigerant line, that's not your warranty claim to fix for free.

Spelling these out as a numbered list in plain language — not legal jargon — reduces disputes. Most customers accept reasonable exclusions when they can read and understand them.

How to price warranty risk into your quotes

Every warranty call costs you real money: drive time, labor, and possibly materials. That cost belongs in your quote before the job starts, not absorbed as a surprise after the callback comes in.

Here's a simple way to think about it: say you do 50 HVAC replacements per year with a 2-year warranty and a 3% callback rate over that window. That's roughly 1–2 callbacks per year. Each one costs 2–3 hours of labor plus any parts. At a $95/hr loaded rate, that's $190–$285 per callback.

Spread that across all 50 installs and you're looking at roughly $6–$7 per job in expected warranty cost. That's not zero, and it belongs in your overhead line when you set your rate. Use the markup calculator at JobEstimator to layer warranty exposure — alongside your other overhead costs — into your pricing before sending the first number.

One more angle: a deposit collected before work begins protects your cash position when a warranty callback eventually arrives. If you're still chasing final payment when the call comes in, you're solving two problems at once. See more on how to collect a deposit as a contractor.

Also: if a customer calls during the warranty period and the visit reveals work beyond what the warranty covers — a separate system failure, damage they caused, additional scope — that's a new job. Write a change order, not a free fix.

Takeaways

• You already have an implied warranty in every customer contract — a written one defines and limits it, which works in your favor.
• The NAHB 1-2-10 framework gives you the starting reference: 12 months for most repairs, 24 months for system replacements, 60 months for roofing.
• Start the warranty clock at final payment, not at the installation date.
• Exclusions earn their keep: manufacturer defects, acts of God, improper maintenance, and customer modifications are not your obligation to cover.
• Price warranty callbacks into your rate before the job starts — the cost is real and predictable even if the timing isn't.

Put your warranty in writing before the next callback

The contractors who handle warranty situations without drama are the ones who decided what the warranty meant before anyone picked up the phone. A clear paragraph in your estimate, adjusted by job type, handles 95% of what comes up. No lawyer required for most residential service work.

JobEstimator makes it straightforward to include your standard warranty language in the scope section of every quote you send. Plans start at $39/mo, and the markup calculator helps you factor expected callback cost into your rate so the price you quote already accounts for the warranty you're standing behind.

The next quote you send is the right time to start.