Three warning signs you have a moisture problem and how to verify it

There is an often-unseen problem lurking in many homes across the country: moisture intrusion. A little excess water in the wrong place can cause many other problems, such as mold growth, pest infestations, and weakened building structures.

In many cases, moisture problems in houses or other structures are easy to miss until they've progressed past the point of easy repair. Early detection of these problems is a must for minimizing the extent and cost of the damage. But, how can you identify a moisture problem in the first place?

There are a few warning signs that homeowners should be on the lookout for, including:

1. Musty odors

One of the most frequently-encountered signs of a moisture problem is the presence of strong, musty odors. This olfactory warning sign is a strong indicator that there is water damage somewhere nearby - possibly in building materials hidden from your direct view, such as in the insulation behind your walls or in a crawl space that you may have difficulty reaching unaided.

This odor is often caused by bacteria and mold growth that feeds on the excess moisture in a dark, cool space. If left alone long enough, the spores from mold can become a respiratory hazard, and the affected area may start showing visible signs of rot.

What does moisture content in wood mean?

Moisture meters are specialized devices that are designed to use either electrical resistance (pin-type) or electromagnetic radio frequencies (pinless type) to measure the amount of moisture in some kind of material - such as wood.

One question that a lot of do-it-yourself enthusiasts who aren't as familiar with the need to monitor moisture in wood and other building materials tend to ask is: "what does moisture content in wood mean?"

Why the moisture content of wood matters

When dealing with wood for flooring and other applications, the moisture content of that wood can have an enormous impact on the quality of the wood.

For example, in wood flooring, if the wood is too dry during installation, it may end up absorbing moisture from the air at the installation site. This can cause the wood to start swelling so planks push up against one another after installation. Or, the wood may split and crack.

On the other hand, an excess of moisture in wood can cause other problems, including, but not limited to:

• Preventing adhesives from making a secure bond;
• Promoting the growth of mold in the wood; and
• Shrinkage as the excess moisture leaves the wood.

The further the wood is from having an appropriate moisture content for the environment it will be used in, the more pronounced these problems will be.

This is why anyone working with flooring and wood products needs to use a moisture meter to measure the %MC of wood. With a moisture meter for wood, it is possible to get an accurate, quantitative measurement of wood's moisture content - which is invaluable for determining if the wood is at risk of developing problems later on.

Using wood moisture meters

Using a moisture meter to check the %MC of wood is relatively simple whether you're using a pin-type or pinless-type meter.

With a pin meter, you simply insert the pins into the wood as deeply as you like, and push a button to get a measurement of the wood's moisture content. With a pinless meter, you can just press the scanning plate against the wood so it's flush with the wood's surface. Then, push the button to get a reading.

One thing to keep in mind is that a wood moisture meter is typically calibrated to get accurate readings in one species of wood. Other species of wood have different physical properties that may throw off moisture measurements. For this reason, it's important to know what kind of wood you're testing, and to use a species correction chart to adjust your reading results.

Five steps to do a concrete moisture test

For any flooring installer and inspector, testing the moisture of concrete can be a pain. Unlike wood or other building materials with a consistent set of physical properties, concrete can have countless different properties from one batch to the next, even when two mixes come from the same manufacturer!

This prevents concrete from having a consistent electrical resistance value to allow pin-type moisture meters to get accurate readings. The variable density of concrete mixes means that there is no consistent specific gravity value for pinless meters to be calibrated to, either.

Calcium chloride tests are another popular testing method. However, they only reveal the moisture conditions in the top layer of the slab. Because of this, these tests miss the moisture conditions in the deeper layers of the slab, where the majority of the moisture resides. So, while useful for determining if the slab is ready for a chemical sealant to be applied, a calcium chloride test doesn't provide the whole picture to a contractor.

So, how can contractors perform reliable concrete moisture tests, ones that generate quantifiable results that can be used to guide installation decisions?

The best way to get accurate information about the moisture conditions deep inside of a concrete slab is to follow the ASTM F-2170 standard, which was recently updated by ASTM to a 24 hour waiting period.

The five steps of measuring moisture using ASTM F-2170

Testing concrete moisture under the F-2170 standard is a process that involves several different steps:

1. Drill the holes for the In-Situ probes: The process begins with the preparation of multiple holes in the concrete for the installation of the in-situ probes. The holes should be ⅝" in diameter and be drilled to a depth equal to 40% of the slab's thickness. For a concrete slab with 1000 ft² of area or less, three holes should be prepared. Larger slabs will need on extra hole per 1000 ft² of surface area. Rotary hammer drills with drill bits that have three or four cutting edges are generally recommended for this task.
2. Clean the holes: After the holes are drilled, they should be vacuumed to remove loose concrete chunks. The sides of the hole should be brushed with a wire brush to knock loose any debris, then the holes vacuumed again.
3. Seal the prepared holes for acclimation: The next step after cleaning the holes is to seal them so they can acclimate to the conditions deep in the slab without being contaminated by outside air. For this, you'll need some specialized sleeves. Once the sleeves are in the holes, seal the gap with silicone or a similar water-resistant sealant. Finish installing the sleeves by using a hammer or rubber mallet to make sure the sleeves are in tight, and cap them with their appropriate lids.
4. Wait 24 hours: After sealing the holes, give them 24 hours to completely acclimate to the conditions in the concrete slab. The ASTM standard used to require a 72-hour wait, but this was changed by the ASTM F06 committee.
5. Insert your probes and start taking readings: Once the holes you've prepared have been given sufficient time to acclimate, remove the cap, insert the in-situ probe (connected to a thermo-hygrometer), and start taking readings! If you want to, you can leave probes in the holes to repeat tests over time as needed. However, if you leave any probes in a concrete hole for 30 days or more, it will need to have its calibration checked before you can consider readings from that probe valid under ASTM standards.

Using this process, you can gather quantitative data about the moisture conditions deep in the slab - which is useful for determining your risk of moisture-related problems later on.