Editor’s note: This post has been updated in 2026 with current Washington State requirements and clearer guidance on what’s state law versus local code.
Washington State has a few safety requirements that can catch home sellers off guard during the appraisal. When these items aren’t installed—or the appraiser can’t easily find them—the appraiser or underwriter will typically require them before closing. That can mean a second trip to the property, a re‑inspection fee, and a delayed closing date.
Here’s what to check before the appraiser shows up.
Carbon monoxide detectors
Washington law (RCW 19.27.530) requires carbon monoxide alarms in residential properties. For a home sale, the seller is responsible for making sure CO alarms are installed before the buyer occupies the home—this applies even if you’ve owned the home since before the law took effect in 2009. WAC 51‑51‑0315 has the installation specifics: generally one alarm per floor and outside each sleeping area.
If you’re refinancing rather than selling, this requirement doesn’t automatically apply to you in the same way—but it’s worth having working CO alarms installed regardless. It’s cheap insurance, and it can prevent a surprise if your loan program calls for a habitability check.
Earthquake straps on water heaters
Unlike CO alarms, water heater strapping isn’t governed by one uniform statewide law that applies to every existing home—it’s mainly a building‑code requirement tied to permits, new construction, and specific local jurisdictions. That said, it’s become such a routine expectation on appraisals and inspections that I’d recommend having it done regardless of whether your specific city or county technically requires it for your situation. It’s inexpensive, it’s a real safety measure in earthquake country, and it removes one more thing that could hold up your appraisal.
Check with your local building department if you want to confirm whether strapping is required for your specific property.
Smoke detectors
This one comes up less often than missing CO alarms, but it’s an easy fix: make sure your smoke detectors are functioning and the batteries are fresh. Like water heater strapping, specific smoke‑detector requirements can vary by local jurisdiction and by whether the home has had recent permitted work—check with your city or county if you want the exact code that applies to your home.
Tips for buyers, sellers, and real estate brokers
- Selling your home? Install CO alarms and consider water heater straps and fresh smoke detector batteries before the appraisal, not after.
- Refinancing? These items may still come up depending on your loan program and when you purchased the home—it’s better to have them in place than to find out at appraisal.
- Real estate brokers: consider attending the appraisal inspection, even briefly, so you can point out where the CO alarms are installed. It can save a callback.
Nobody likes paying for a re‑inspection fee—or watching a closing date slip—over something this easy to fix ahead of time.
Frequently asked questions
Do I need a carbon monoxide detector if I’m not selling my home?
Washington law requires them at time of sale, but it’s good practice to have working CO alarms installed at any time, sale or no sale.
Are water heater earthquake straps required by law in Washington?
Not universally for every existing home—it depends on your local building code and permit history. It’s commonly expected on appraisals and inspections, so many sellers install them proactively.
Will a missing smoke detector delay my closing?
It can, if the appraiser or underwriter flags it and requires it be corrected before closing. It’s a quick, inexpensive fix to handle ahead of time. Related topics:
Appraisal Guide for Washington Homebuyers
Last reviewed: September 2026
About Rhonda Porter
You mention CO2 detectors in your article. I’m not sure they exist. If they do, they’d be going off all the time since we breathe out CO2 (Carbon Dioxide). Do you mean CO (Carbon Monoxide) detectors?
Thanks, Bob. I specialize in helping people buy or refi homes – not chemistry! Post has been corrected.
I just re-read my post. Sorry for sounding so snarky! I was trying to be funny but sarcasm never translates properly online. 🙂
No worries!!! 🙂
Rhonda – please look at the law. Don’t tell us what you think it says, tell us what it says. Maybe pay an attorney to give legal advice.
Other people are quoting your advice, as law.
Owner, first of all, I am not an attorney — I’m a mortgage originator. I state that throughout this blog. Please point out where on this post that I have stated something that you feel is not correct — that would be more helpful.
Then don’t give legal advice.
Carbon Monoxide alarms are required when selling an owner – occupied single family residence after July 26, 2009.
No similar law applies to smoke detection devices or water heaters, unless it is new construction or a new installation. So for the majority of homes in Washington – this would not apply.
I have updated the post to include links for your reference.
I’m curious why you’re commenting with an alias?