It's difficult to imagine life without moisture. It's unavoidable even in your own house. Running baths, boiling water, breathing, and even the components that make up your house interact with exterior air to produce humidity, which is a measure of the amount of moisture in the air. Proper building methods, on the other hand, are meant to prevent moisture intrusion inside your walls. The external walls are often coated with a moisture barrier and siding, with additional moisture barrier beneath the sheathing. In most circumstances, it is sufficient to prevent the water from soaking in the wall material. However, if there is a leak, the water can quickly saturate the wall and promote mildew or rot. Begin with manual checks before moving on to moisture metres to test for moisture inside the walls.
Take a close look at the wall's surface. Examine the surface for deterioration, such as yellowing material, rounded brown patches, or black, often furry-looking discolorations that indicate mould and mildew growth. Pay great attention to the texture of the wall. Peeling paint, combined with warped or buckling surfaces, is a sure sign of moisture problems.
Push a little harder on the wall to see how it feels. Moisture-damaged drywall will feel mushy and spongy, but wood-sheathed walls may feel slightly substantial even when wet. A butter knife, screwdriver, or other similar instrument scraped across the surface or slightly probed into it may frequently show damaged wood.
Smell the wall to check for dampness. When the interior of a wall becomes damp, it creates an ideal habitat for mildew and mould to grow: it's dark, moist, and there's plenty of food available for the fungus. The more moisture there is, the faster mould grows and wood rot develops. If the wall smells musty, there's a problem. Occasionally, removing the faceplate from a wall outlet to get your nose closer to the inside of the wall can help you find the problem more quickly.
Drill two tiny holes into the wall, about 3/16 inch in diameter and 1 inch apart. Work from the inside or outside of the house – either way works. Outside, drill just deep enough to penetrate through the siding without piercing the outer wall sheathing. Drill through the wall, through the vapour barrier, and into the insulation.
In the drilled holes, insert probes from a probe moisture metre. Turn on the metre and read the moisture content display according to the manufacturer's instructions. Adjust the probes as needed to achieve a consistent reading and accurate results. Taking numerous readings spread out across time, such as three readings in a half hour, is beneficial.
Compare the reading with the recommended moisture levels. Zero moisture is unattainable; even wood used to structure a home has some moisture. Normal values range from 7 to 13 percent moisture. Slightly higher readings may be typical for your home, but very high levels necessitate prompt action.
Fill the test holes if visual and mechanical data show that the moisture levels inside your wall are normal. Outside, inject coloured or clear silicone caulk into the hole to fill it and seal it. To patch holes within the home, use wood putty or spackling compound and drywall tape. If you have a moisture problem, you may need to pull off the wall sheathing in order to fix the interior. That's why it's better to hire professionals rather than doing yourself.
Tip: Before testing your wall, calibrate the moisture metre according to the manufacturer's recommendations.
Other types of metres are available, ranging from those that employ electromagnetic waves to detect moisture beneath the wall surface without the need of probes to simple desiccant spikes that slot into probe holes and are taped over. Check the spikes after a few hours; if they transition from yellow to green, you have too much moisture.