Finding Mold Using Moisture Meters

The CMHC reports “too much moisture in the air can lead to mold” — finding it can help prevent or stop mold. Many mold inspectors use moisture meters to find wet areas where mold may be growing.

These meters measure the moisture in many types of building materials (see Mold Problems From Wet Framing Lumber During Construction). They also can monitor the process of drying these materials. Moisture meters help you figure out whether your building materials are too wet. They typically use electrical conductivity between a couple of metal pins to assess moisture content; the more moisture in the material, the greater the electrical conductivity. The moisture content is measured as a percentage of total weight.. Moisture meters can be used on carpet, wallboard, wood, brick, and concrete. Because black mold often grows where moisture is high, a moisture meter can help an investigator locate hidden areas of mold growth.

In mold inspection  pin and surface meters are use to determine if there is a moisture problem or  potential toxic mold problem.

surface mold moisture metersSurface Mold Meters, Pinless or Search Mode

With surface moisture meters you don’t make holes in the surfaces you are testing. They are good for finding moisture behind tile or drywall. They are also effective finding condensation, water pools in ceilings or in damaged plumbing it can take readings 3/4 inch deep. It is similar to a stud finder.

Pinless mode, also known as search mode measures moisture behind surfaces. In this mode  the meters emit electric current or radio waves that respond to moisture. They calculate the moisture content by comparing data bounced back to them.  They detect the amplitude of returning waves. When the waves contact water they are diminished.

Search mode is commonly used in the following locations:

  • in showers and bathtubs. Possible locations of water leaks are usually from holes made for shower heads or faucets. Water leaks can come from the shower or behind the wall from  internal plumbing .
  • dishwasher leaks that may allow water to absorb or pool in surrounding kitchen flooring or other materials.
  • the sub-floor under a bathroom floor.
  • looking behind covered walls or floors, such as a tile or vinyl.

pin type moisture meterPin Moisture Meters

A pin moisture meter is good to get a reading from a deeper depth. Pin moisture meters are good for testing the moisture content of concrete and framing lumber. They are also effective for looking in or behind plaster, carpet, baseboards, hardwood flooring and gypsum boards. It also has a percentage scale that can tell just how wet an item is. If you test behind baseboards and get a measure above sixteen percent there is a strong possibility that mold is present. Note that mold needs 16% moisture levels to grow. It is important to check that framing levels test below 16% before you close it in with drywall.

There is an impressive array of pin moisture meters with varying types and lengths of metallic pins that extend the reach of the electrodes. Some probes can measure the moisture content from deep in straw homes walls. Some work by inserting into drilled holes in masonry. Other probes can be hammered into wood then pulled out. Log homes can have moisture content evaluated by measuring 2/3 away from the log surface to center.

Moisture meters are a small investment when one considers the potential cost of mold removal from structural materials and professional mold abatement.

You may also want to refer to How to control humidity, Understanding home moisture and What is moisture?