A Yearly Home Moisture Checkup: What to Look At

An annual home moisture inspection is a planned walk through the house, from the attic down to the foundation, looking for stains, damp materials, musty smells and anything that has changed since last year. It takes about an hour with a flashlight and a notepad. Moisture problems grow slowly and out of sight, so a yearly look in the same places is the most reliable way to catch them while they are small and cheap to fix.

When to do it and what you need

Pick the same time each year so you can compare. Late winter or early spring works well in Ontario, because the attic shows signs of winter condensation and the basement shows how it handled the melt. Bring a bright flashlight, your phone for photos, a notepad and a digital hygrometer. A basic pin-type moisture meter from a hardware store costs roughly $40 to $60 and is useful for checking wood and drywall. Take photos of the same spots every year. Comparing them tells you more than memory does.

Annual home moisture inspection checklist: attic and top floor

• Look into the attic from the hatch, or walk it only if there is safe footing. Check the underside of the roof boards for dark staining, frost in cold weather or water trails.
• Check around the plumbing stack, chimney and roof vents for stains on the wood below.
• Confirm bathroom fan ducts are attached and run to the outside.
• Look for insulation that is matted, stained or compressed, which suggests it has been wet.
• Notice the smell. A healthy attic smells like dry wood and dust.
• On the top floor, scan every ceiling for brown rings, hairline stains or bubbling paint, especially below the attic hatch, bathrooms and roof valleys.
• Check inside closets on outside walls and behind large furniture for spotting or a stale smell.

Main floor, kitchens and bathrooms

• Empty the cabinet under each sink and look at the floor of the cabinet, the trap and the valves. Feel for dampness and look for swelling or staining.
• Check around toilets for soft or discoloured flooring and confirm the toilet does not rock.
• Press on the tile and walls around tubs and showers. Loose tiles or a spongy feel point to water behind the surface.
• Look at the caulking and grout lines for gaps.
• Pull the fridge, stove and washer out a little and look behind and under them.
• Check window sills and the walls below windows for peeling paint, stains or soft spots.
• Look at ceilings below bathrooms and the laundry for stains.

Basement and mechanical room

• Note the smell when you first open the basement door, before your nose adjusts.
• Read the hygrometer. Leave it downstairs for a day and record the number.
• Walk the perimeter. Look at the base of the foundation walls for damp patches, staining, flaking, or white powdery deposits.
• Check the bottom of finished walls and baseboards for swelling, dark lines or rusted nail heads.
• Look up at the rim joist, where the floor framing sits on the foundation, for dark staining or damp insulation.
• Inspect around the water heater, furnace, humidifier and water softener for drips, rust trails and puddles.
• Check the floor around the sump pit and the floor drain.
• Look into the cold cellar and under the stairs, which are closed, cool and often forgotten.
• If you have a crawlspace, shine a light in and look at the joists and the ground cover.

What your findings mean

Not every mark is an active problem. An old, dry stain with sharp edges may be from a leak fixed years ago. This is where the moisture meter helps. Dry framing and drywall give low, steady readings. A reading that is clearly higher in one spot than in the same material a metre away tells you that area is wet now. As a reference, we look for wood framing to read under 16 percent moisture content before we call it dry.

Write down anything that is damp, soft, smelly or new, with the date and a photo. Fix the simple causes yourself. Recheck in two weeks. If a spot is still wet, getting bigger, or you cannot find the source, it is time for a closer look.

When to bring in a professional moisture check

Some moisture cannot be found by eye. A thermal camera shows temperature differences on walls and ceilings that often trace the path of hidden water, and a professional moisture meter confirms whether the material is wet. That combination is useful for a stain with no obvious source, a musty smell with nothing visible, a house you are about to buy or sell, or a check after a leak repair to confirm everything has dried.

We offer a yearly moisture check as part of our prevention service, using a thermal camera and moisture meter, with photos and readings you can keep on file. An inspection typically runs $249 to $549. Indoor mold should be removed when it is found, whatever the type, and anyone with health concerns should speak to a doctor.

Put a recurring reminder in your calendar for the same weekend each year. Keep your notes and photos in one folder so each inspection starts with last year's results in hand.

Common questions