How do you check for moisture behind walls?

Author: Renee Yost  |  Last update: Friday, March 7, 2025

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

How to tell if there is moisture behind a wall?

Moisture and water that get behind the wall cause the backside of the drywall to soften and even become mushy. Look for soft spots or wet spots in the drywall and gently press into them. If the drywall depresses, there is most likely water damage. Mold on your walls' surfaces.

What do home inspectors use to detect moisture?

A moisture meter is used to measure the percentage of water in a material. The inspector can use it to test the roof decking, support beams, pillars, and other elements for their moisture content. It's common to find areas on the roof where the flashing and roof covering are in less-than-optimal shape.

How do you know if there is water damage behind drywall?

Signs of water damage in drywall usually include peeling paint, staining, or a musty smell. If you have a leaky pipe, you might also notice a significant jump in your water bill.

How do you test for dampness in walls?

Foil test: If you've noticed a damp problem but aren't sure if it's caused by condensation or penetrating or rising damp, you can use a foil test. Tape a square of aluminium foil to the wall and leave it there for a day. On inspection, if the side facing away from the wall is wet, you have an issue with condensation.

How to Use a Moisture Meter | Ask This Old House

Will a dehumidifier remove damp from walls?

Dehumidifiers can indeed aid in drying wet walls. After a flood, leak, or a spell of extreme humidity, damp walls can develop. A dehumidifier removes extra moisture from the air, lowers the humidity, and stimulates evaporation.

What are the first signs of damp in a house?

Signs of damp to look out for
  • Wet walls and ceilings, and staining. If your walls or ceilings feel damp to touch, or you spot brown or yellow-tinged stains appearing on plaster, it's likely you have a damp problem.
  • Black mould on walls. ...
  • Peeling wallpaper and crumbling plaster. ...
  • A damp, musty smell. ...
  • Rotting skirting boards.

How do you fix moisture behind drywall?

Dry the water damaged walls

Use high-efficiency blowers and dehumidifiers and open the windows and doors. Use fans to increase air flow behind walls and leave them running for at least two days so the studs and flooring can completely dry.

How do plumbers find leaks behind walls?

Thermal imaging can be used to detect moisture in ceilings, flat roofs, behind walls and under floors. Using thermal imaging cameras is an effective way to look at large areas quickly, and causes minimum disruption and no damage to your property.

Is water damage covered by insurance?

Under most standard home insurance policies, if water damage occurs suddenly or accidentally from a source inside your home, such as a busted pipe, it will likely be covered by your homeowners insurance. If the water comes from outside your home, it will not be covered by your standard policy.

Who can check for moisture in a house?

Companies that provide water damage inspection services may help look for moisture and some may be familiar with mold problems as well.

Do moisture meters really work?

Are Moisture Meters Accurate? High-quality moisture meters can achieve an accuracy within 0.1% of the wood's moisture content, offering consistent and reliable readings. The accuracy largely depends on the meter's quality and brand. The accuracy of the less expensive digital moisture meter can vary from 5 to 20%.

How do I check for moisture under my house?

Check Wood Moisture Levels in Crawlspace

One way to determine if your crawlspace has a moisture issue is to check the wood moisture content using a wood moisture meter. These handheld devices are able to tell you if your subfloors and floor joists are holding excessive moisture.

Is there an app to detect moisture in walls?

The moisture mapping app records wall and concrete floor moisture reading details in all areas, making it easy for users to get the details they need quickly and easily from any mobile device.

How do you remove moisture from inside walls?

Use fans to move air around the damp walls. Also use dehumidifiers, which can help remove moisture from the air and walls. Professionals use tools like moisture meters, infrared imaging devices, dehumidifiers and heavy-duty fans. That ensures the walls are truly dry before further repair, painting or refinishing.

What does water damage behind wall look like?

As with other rooms, flaking, bubbling paint is another sign of water-damaged basement walls, along with wood rot and uneven or sinking floors surrounding the walls in question. Noted earlier, warped, bowing walls with yellow-brown stains are also signs of water damage in your basement walls.

How much does a water leak behind a wall cost?

Fixing an exposed pipe in a crawl space or basement is $150 while repairing a leaky pipe inside a wall starts at $150 and can go up to $350 or more. A pipe in the wall behind a kitchen cabinet will cost $500; if the faulty pipe is in a ceiling, it can cost $700 to $2,500.

How do you know if your water is leaking behind the wall?

Step 1: Look for Visible Signs of Water Damage

Some common signs include wet walls, wet spots on floors or ceilings, peeling or bubbling paint or wallpaper, sagging walls or ceilings, discolored patches on walls or ceilings, and a musty smell.

How do you check for water pipes behind walls?

Pipe finders are designed to identify where electrical cables or gas and water pipes are located inside a wall. This is especially helpful if piping isn't visible or when doing building work on a property you're unfamiliar with.

How do you measure moisture behind drywall?

How to detect moisture behind walls? Moisture within and behind walls can be detected with a pinless moisture meter. A non-destructive moisture meter can accurately locate and measure elevated moisture levels without the need to break the wall's surface material.

Will mold always grow on wet drywall?

No mold doesn't always grow after a leak. If the temperature isn't right or if the leak is properly dealt with quickly, there's a chance that mold spores won't be able to take root or grow.

How do you dehumidify behind a wall?

To dry out small spots, place a fan in front of the damp area and turn it on high. For larger spots, install a heavy-duty dehumidifier in the room to suck the water vapor out. If you need to dry out a wall in an enclosed area, place moisture absorbent materials like dehumidifier packs near the damp spots.

How to test a wall for damp?

If necessary an overnight test can be carried out by sticking down a patch of clear plastic sheeting with insulation tape, moisture under the plastic sheet the next day indicates a damp problem.

Is damp covered by insurance?

The worse a damp situation gets, the more it's likely to cost to repair any damage. Most standard buildings and contents home insurance policies do not cover damage caused by damp and condensation.

Will a dehumidifier get rid of damp?

Dehumidifiers seem to be the obvious way of reducing humidity, removing condensation, stopping walls becoming damp and preventing mould. But a more effective solution is to give your home a small but consistent background movement of fresh air. This will help keep your home feeling fresher, healthier and mould free.

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