How to Check a Mold Company in Washington Before You Hire

Does Washington license mold remediation companies?

No. The Washington State Department of Health says there are no specific certification requirements for mold or water damage restoration work in the state, and that anyone can call themselves a mold remediation specialist without training or credentials. Voluntary training and certification exist through groups such as the IICRC, and they can show a company has invested in training, but they are not a state requirement and they are not a guarantee of quality.

For indoor air or mold consulting, DOH points people to the AIHA consultant directory, which lists industrial hygiene and environmental consulting firms. That can be a useful route when you want an assessment from someone who does not do removal work.

What Washington does require is contractor registration. Under RCW 18.27.010, anyone who, as an independent business, undertakes, offers to undertake or bids on construction, alteration, repair or demolition of a building counts as a contractor. Tearing out moldy drywall and rebuilding a wall falls in that territory, and the law covers offering or bidding on the work, not just doing it.

What does L&I registration involve?

According to L&I, all construction contractors must register with the department. Registration comes in two main types:

• General contractors may work across trades and hire subcontractors.
• Specialty contractors may work only in their registered specialty and cannot hire subcontractors.

To register, a company posts a continuous contractor surety bond of $30,000 for general contractors or $15,000 for specialty contractors (the higher amounts apply to renewals dated July 1, 2024 or later) and carries general liability coverage of $200,000 public liability and $50,000 property damage, or a $250,000 combined single limit. A bond of that size is a floor, not a full safety net for a large job, which is one reason the other checks below matter.

How do you use L&I's Verify tool?

1. Search the exact business name that appears on the bid, or the registration number if the company lists one. Small differences in name can mean a different entity.
2. Confirm the registration is active, not expired or suspended.
3. Look at the registration type. A specialty registration in an unrelated trade, or a specialty contractor planning to bring in subcontractors, is worth a question.
4. Check workers' comp. The tool shows whether the business has an active workers' compensation account covering employees.
5. Review bond claims and citations. Verify lists lawsuits against the bond and any safety or construction citations. One old item is not automatically disqualifying; a pattern is.

It takes a few minutes and it is the single most useful check available in Washington, because no mold-specific state credential exists to look up instead.

Should the same company test and remove the mold?

Washington has no rule requiring different companies for assessment and removal. Even so, Angi recommends using separate companies for mold testing and remediation, and many homeowners find that an independent assessor gives a clearer picture of what really needs to be removed. The same logic applies at the end: post-remediation testing done by someone without a stake in the removal job gives you a neutral sign-off. Our guide to mold inspection versus mold testing explains what each visit should produce.

Be wary of a sales pitch built around lab results when the mold is already visible. EPA says that in most cases, if visible mold is present, sampling is unnecessary, and there are no EPA or federal limits for mold or spores. Surface sampling can be useful to confirm an area was cleaned adequately.

What should a written bid include?

L&I's Hire Smart steps recommend getting bids in writing from several registered contractors. The contract should state the price including sales tax, the payment terms, the specific work, and the materials and any subcontractors. Changes should be in writing too. For mold work, add the items below so you can compare bids line by line.

For a sense of scale, Angi's Seattle cost guide reports mold remediation in Seattle averaging $1,988, with most jobs between $1,008 and $2,967 depending on location, mold type and size. Wall and whole-house jobs run far higher. Our Seattle mold removal cost guide breaks the ranges down by area of the home.

What questions should you ask on the walkthrough?

• Where do you think the water is coming from, and how will we confirm it?
• Is the affected area more or less than about 10 square feet? (EPA and DOH both use that line for when to consider a professional.)
• What will be removed versus cleaned, and why?
• Who handles the rebuild after removal, and is that priced here?
• Will you send crews or subcontractors, and are they on your L&I registration?
• Who decides the work is finished, and what will that check look like?

It also helps to ask how long the job will take, whether you can stay in the home while work is under way, and what you should move out of the area beforehand. A company that has thought through those details for your floor plan is more likely to have thought through the rest.

Good answers sound specific to your house. Vague answers that skip the moisture source are a warning, because EPA is blunt that mold returns if the water problem is not fixed. Reading up on what happens during mold remediation beforehand makes it easier to judge.

How should you handle payment and liens?

L&I advises paying as phases of work are completed rather than in full up front, and asking for lien releases before the final payment. Under Washington's process, a lien may be filed within 90 days of when work stops or materials are delivered, so a supplier or subcontractor who was not paid by the company could otherwise come after your property. Keep copies of the contract, change orders, receipts and any clearance results together.

What are the red flags?

• Claims of a Washington state mold license or certification. None exists, according to DOH.
• No active L&I registration, or a business name that does not match the registration.
• Scare language about color. Color does not tell you how risky a mold is; see black mold: facts versus fear.
• Painting or spraying over growth without removing it. EPA says not to paint or caulk over mold.
• Large deposits demanded before any work starts, or pressure to sign that day.
• No plan for the water source.

Does any of this change for businesses or homes outside Seattle?

The state rules are the same anywhere in Washington. A landlord or business owner arranging commercial mold remediation should run the same Verify check and ask for the same written scope, with attention to occupants and building systems. Homeowners comparing bids for mold remediation in Tacoma or on the Eastside in Kirkland can use the identical checklist. If you are still sorting out what the problem is, start with a mold inspection in Seattle; if removal is clearly needed, our page on Seattle mold remediation covers what the work involves. You can also browse all mold services.