Mold Inspection for Cabins and Vacation Rentals in North Idaho

We test for mold in cabins, lake places and vacation rentals across North Idaho, from the Coeur d'Alene area north to Sandpoint, Priest River and Bonners Ferry and east into the Silver Valley. We do not remediate and we take no referral fees from companies that do.

This page is for people opening a cabin in spring, short-term rental owners with a guest complaint, and buyers of seasonal property. In each case the building sat for months with nobody in it, and the useful work is finding out whether anything got wet during that time.

What a closed building does over a North Idaho winter

The 2020 census counted about one in four housing units in Bonner County, 25.4 percent, as vacant, a category that includes cabins and second homes held for seasonal or occasional use. A seasonal building spends the winter either with the heat off and the water drained, or with the heat turned down to protect the pipes.

Cold surfaces and rising relative humidity. When air cools, its relative humidity rises even though no water has been added. A cold building with no fans running and no doors opening can hold damp air against its coldest surfaces for weeks: exterior wall corners, closets on outside walls, the underside of the roof deck and the crawl space. The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50. A closed cabin with no dehumidification and no air movement has nothing working to hold it there.

Snow on and around the building. NOAA's 1991 to 2020 climate normals put average annual snowfall at 62 inches in Sandpoint, about 54 in Bonners Ferry, 56 in St. Maries and nearly 76 in Wallace. That snow sits on roofs, slides off and piles against walls and decks. A partly heated building can lose enough heat through the ceiling to melt snow on the upper roof, and the meltwater can refreeze at the cold eave into an ice dam that pushes water under the shingles. Snow banked against siding holds water against the bottom of the wall for months. See ice dams and attic moisture.

The spring thaw. When that snow melts, a lot of water arrives at the foundation in a short window, often while the ground underneath is still frozen and cannot take it in. A crawl space that is dry in August can take water in March, and in a seasonal place nobody is there to see it. See snowmelt basement seepage.

Plumbing that froze. A supply line that froze in January may not leak until it thaws, or until someone turns the water back on in May. A split pipe or a failed fitting can run into a wall or floor cavity for a long time before anyone is on site to shut it off. See mold after a burst pipe.

None of this means a closed building will grow mold. It means that if something went wrong, it went wrong with nobody watching, and the first person to find out is whoever opens the door.

Opening a cabin in spring

A building that has been shut for five or six months will smell stale. That smell by itself is not a finding, and it is not a reason to pay for a lab test. Do this first:

1. Walk the whole building before turning the water back on. Look at ceilings below the roof, especially near exterior walls and at the eaves. Look under sinks, behind toilets, at the water heater and along any supply line in an exterior wall.
2. Turn the water on and watch it. Check the same places again after an hour and again the next day.
3. Bring the building up to normal temperature and ventilate it hard for several days. Open windows when the weather allows and run the bath and kitchen fans.
4. Look in the crawl space if you can get to it. Standing water, wet insulation sagging from the floor, or damp soil along the foundation walls tells you more than a smell does.

If the smell is gone after several days of heat and fresh air, the building was stale. If it persists, if it is concentrated in one room or closet, or if you found a ceiling stain, a wet floor or a pipe that let go, that is when testing tells you something.

Short-term rental owners with a guest complaint

A guest reports a musty smell or says they felt unwell, and it ends up in a review. You want to know whether there is a real problem, and you want something on paper either way.

An inspection gives you a moisture survey of the building, thermal imaging to find wet or cold areas in walls and ceilings, and air samples compared against an outdoor control taken the same day. It shows whether the spore levels and types indoors resemble the outdoor air or differ from it, and it points to where moisture is, if there is any.

Be clear about what it cannot do. An air sample describes the air during the minutes it was collected. It cannot tell you what the air was like during a stay last week, and no test can establish that a particular guest's symptoms came from mold. The EPA notes that no EPA or other federal limits have been set for mold or mold spores, so no report can certify a building as safe or compliant. What a report can do is document conditions on a specific date, with the raw lab data attached.

Sampling works best when the building has been closed up for several hours, with no cleaning crew running fans or spraying product right before we arrive. If you manage several units, see the page for property managers.

Buying a seasonal property

Cabins are usually shown in summer, when the building is open, warm and dry. The failures above happen in winter and spring, and a summer walkthrough can miss them.

Ask the seller for the winter history. Was the heat left on, and at what setting? Was the water drained? Who checked on the place, and how often? Were there any pipe breaks, roof leaks or water in the crawl space? In most Idaho residential sales the seller fills out a property condition disclosure, and its questions about basement water, the roof, plumbing and drainage matter more on a cabin than on a house someone lives in year round. See what Idaho's disclosure law covers.

During your inspection period, put the testing where the building's winter history points: the crawl space, the ceilings at the eaves, the plumbing walls, and any addition or enclosed porch where two roof lines meet. A moisture reading and a thermal scan at those spots often says more than an extra air sample in the living room. For waterfront property, see lake home mold inspection.

What testing can and cannot tell you

• It can show whether indoor spore levels and types differ from the outdoor air on the same day.
• It can find wet materials with a moisture meter and thermal imaging, which in a building that sat closed is often the more useful result.
• It cannot see inside a wall. Moisture readings and thermal imaging narrow down where to look. Confirming growth inside a cavity means opening it.
• It cannot give you a pass or fail against a legal limit, because there is no federal limit to measure against.

What the visit covers and what it costs

A standard inspection is $425. It includes the site visit, moisture mapping, thermal imaging, one indoor air sample plus an outdoor control, all lab fees and a written report. Additional samples are $100 each, whether air, tape lift or swab, and a typical three-sample job comes to about $525. Homes over 3,000 square feet are $550 to $650. Lab results come back in 1 to 3 business days, and a 24-hour rush adds $100. There is no trip fee anywhere, including North Idaho. Details are on the pricing page.

Jesse Futia, a NORMI Certified IAQ/Mold Assessor, does the inspection, collects the samples and writes the report. Idaho does not issue mold inspector or assessor licenses, and neither does Washington. See Idaho mold testing rules.

Frequently asked questions

My cabin smells musty every spring. Should I test? Not first. Walk the building, turn the water on and watch it, then heat and ventilate the place for several days. A building that has been shut all winter smells stale, and that alone is not a finding. If the smell persists after that, is concentrated in one area, or you found water, testing will tell you something useful.

A guest complained about mold. Can a test prove my rental is fine? No test can certify a building as safe, and no EPA or other federal limits exist for mold spores. A test documents conditions on the day it was taken: moisture readings, thermal images and air samples compared against an outdoor control, with the raw lab data in the report.

How much does a cabin inspection cost? $425 for a standard inspection with one indoor air sample, an outdoor control, lab fees and a written report. Additional samples are $100 each and a typical three-sample job is about $525. Homes over 3,000 square feet are $550 to $650. There is no trip fee anywhere, including North Idaho.

I am buying a lake cabin in summer. What should I ask the seller? Ask whether the heat stayed on through the winter and at what setting, whether the water was drained, who checked on the place and how often, and whether there were pipe breaks, roof leaks or water in the crawl space. Then aim your inspection at the crawl space, the eaves and the plumbing walls.

If you find mold, will you clean it up? No. We only test. We never perform remediation and we take no referral fees from companies that do. After a separate company does the work, we can come back for clearance testing, which is $375 flat for up to three samples.