How to Check for High Moisture Levels in Your Walls

As a homeowner, it’s a sinking feeling when you realize there could be moisture in your wall. You wonder… How far does the moisture go? What will you have to do to stop it? What will you have to replace?

And the big question: how do you know for sure there is moisture in your wall?

It can be unnerving to not know. But in this article, we’ll help you assess whether there’s moisture in your walls and know what tools you can use to do so. Here’s the process:

• The telltale signs of moisture in walls
• How to detect moisture in walls
• How to address moisture in walls

Before we get started, it’s important to note that for this article, we are assuming gypsum drywall is the wall covering, as it’s the most common type. Other types of walls may require different detection tools and/or methods to address the moisture.

Let’s start by looking at ways to find out whether the walls are holding moisture.

The telltale signs of water damage and moisture in walls

You can’t always tell when moisture has invaded a wall. Moisture is elusive. However, many times, a visual inspection will reveal clues that can tip you off to a moisture problem. These clues include:

• Blistering—paint bubbles that appear on the wall
• Stains on the paint, which indicate either water or mold growth. (Even if the problem happened in the past, stains still indicate a problem.)
• Discoloration, such as darker patches on the wall or yellow spots (Mold growth can sometimes look like discoloration.)
• Peeling paint—one step beyond blistering
• Warping, bowing, or uneven surfaces on the wall
• Soft spots in the drywall
• A musty odor

If moisture intrusion has progressed significantly, you may also see things like:

• Mold or mildew, either small black dots or large blotchy areas
• Pest infestations (though this can also be caused by food sitting out or other things, so this shouldn’t be your only clue for water intrusion)
• Crumbling drywall
• Dampness

If you suspect moisture damage from some of these signs, or any other reason, you can take it a step further with a tool for detecting excess moisture in the walls.

How to detect moisture levels in walls

Two main tools are typically used for moisture detection in walls: a thermal or infrared camera and a moisture meter.

A thermal or infrared camera

Both thermal and infrared cameras map the temperatures of a given area. Generally, the warmer the temperature, the brighter or more yellow/red/orange the color will be on the camera. The colder the temperature, the darker blue/gray the color will appear.¹

Water usually cools a surface.

Therefore, if you see a lot of cooler patches as you scan a certain area of the wall, you can assume they indicate the presence of moisture. However, you’ll want to follow up with a moisture meter, just to be sure.

A pinless moisture meter

A moisture meter can be used in conjunction with a thermal camera or all on its own. Either way, it will confirm the presence of moisture in a wall.

However, most moisture meters are calibrated to measure moisture in wood, not drywall, carpet, or other materials. They may work with building materials other than wood, but be aware that they can’t give exact moisture content readings. They aren’t calibrated for anything other than wood.

However, they can usually be put in relative mode, which will give you a rough idea of how much moisture is in the wall. They will provide a scale (such as .2 to 50, with .2 being the driest and 50 being the wettest), and they give a higher reading in areas with more moisture. This can help you figure out the source of the moisture.

Bessemeter meters can be used on concrete and drywall in relative mode.

Both pin-type moisture meters and pinless ones can indicate the presence of moisture in walls. However, it’s easier and less damaging to use a pinless one. With pin meters, you must stick small prongs, or pins, into the wall, leaving small holes.

With pinless meters, though, you only need to hold the sensor pad against the wall and wait for a moisture reading to appear.

How to address moisture in walls

Once you’ve assessed your walls and discovered moisture, here are some steps you can take to address the issue.

1. Identify the cause

Knowing the cause of the moisture issue will help you fix the current damage and prevent it from happening again.

Sometimes it’s a quick fix, such as a pipe bursting and needing replaced.

Other times it could be a continual problem stemming from another source, such as a faulty seal around a chimney, causing a water leak during heavy rain; or melted snow or ice seeping through the roof and into the ceiling below; or failed drain tiling around the foundation allowing excess water to leak into the basement.

And sometimes, condensation may have built up in the walls due to improper building practices or studs that were too wet to begin with.

Whatever the case, try to locate the source of the problem before going further.

2. Stop the cause

Before you can remedy the moisture damage in your wall, you have to stop the problem at its source. Otherwise, moisture will only continue to damage your walls.

You may have to patch or replace piping, or replace shingles or other roof parts. If the caulking is at fault, then replace the caulking and/or sealing around the offending window or door to prevent further water damage.

However, if you aren’t a professional and the problem isn’t something you have experience fixing, it may be best to call in a professional.

3. Dry up the moisture

This can be achieved in a number of ways, but a common method is to set up fans or dryers in the affected area to dry out the walls. If the moisture is deep-set in the walls, you may also have to rip that section of wall out and use a fan on the inside. Insulation may even have to be replaced to prevent mold growth.

Again, if you aren’t familiar with this process, bringing in a professional is probably the best option.

Keep your building sound

Finding moisture in your walls isn’t ideal, but it’s definitely not uncommon. Knowing the signs that indicate moisture, knowing how to actually confirm moisture’s presence, and knowing how to fix the problem are vital to maintaining a sound building.

This is why moisture testing is sometimes a part of home inspections. Moisture is such a significant problem in homes that knowing how to detect it is an incredibly valuable skill for inspectors.

1. “How to Test for Wet Walls, Ceilings, and Construction Materials,” Rendall’s Certified Cleaning Services, YouTube. (↑)