If you suspect moisture damage in your drywall or want to check the quality of the new drywall before you install it, you might be wondering what level of moisture is acceptable in drywall?
Drywall is very sensitive to even a small amount of moisture. Even though it’s not load-bearing and damage to its structural integrity isn’t necessarily dangerous, high moisture levels in drywall will cause it to crumble, crack and deteriorate. In cases where moisture contact is prolonged, mold growth can happen. Very high levels of moisture in drywall make also indicate a more serious problem like water leaks.
This article will discuss what moisture level to look for in drywall, how to read moisture content, and what to do if you suspect a problem.
Table of Contents
The Optimal Moisture Content for Drywall
Moisture content in drywall is acceptable up to 12%, and it’s not uncommon to find installed drywall reading between 5% and 12%. Anything higher than this indicates that the drywall has been moisture-compromised and is susceptible to crumbling and deterioration, though drywall that has not reached above 17% may still be salvageable. Relative humidity levels surrounding the drywall will affect readings, as will the type of moisture meter you use.
Ideally, the moisture content of drywall would be less than 1%. Still, drywall installed and has faced the elements, whether climate-controlled or not, will reflect the area’s relative humidity. A garage during a Florida summer might read near 12% and be ok, but a climate-controlled home in a drier area might be in trouble at that level. It’s more useful when determining if there is a problem. Often it is to use a relative scale to take moisture readings. This allows you to account for humidity in the air.
Sometimes, if you’re looking for a major problem, you don’t need to do anything more than a visual inspection. If a wall is soft, smells mildewy or damp, or has visible water stains or cracks, you can be pretty sure that it has been damaged and needs to be replaced. Crumbling drywall is also an indication that your drywall has prolonged exposure to moisture, and there is likely a larger problem at play even if your moisture meter is giving you a low reading. If you see visible signs of water damage, you need to investigate. Not all moisture meters give accurate readings all the time on all materials.
Drywall Moisture Meters
For accurate moisture content readings, you’ll need a moisture detector. Moisture meters are either pin-type, pinless, or a combination of the two. These moisture testing devices detect moisture content in various building materials, including gypsum, wood, plaster wall, and masonry. Though top-quality moisture meters can range between $600 to over $1000, you can get fairly accurate readings with some affordable models.
Pinless moisture like this Klein Tools Pinless Moisture Meter is good for quickly determining the moisture content over a large area and is convenient. If you need to double-check the quality of your drywall before you hang it, or if you’re doing a basic home inspection. There are different modes for various materials, which makes it easier to use and take to other applications. Pinless moisture meters are non-destructive moisture meters, i.e., you do not have to poke a hole in your drywall to take a measurement. They use an electromagnetic current to determine moisture levels across the surface of the drywall. Most low-end moisture meters detect moisture levels up to 3/4 inches deep but may have trouble on painted or finished surfaces.
- WATER LEAK DETECTOR detects moisture content from leaks and flooding
- PINLESS MOISTURE METER measures moisture content in building materials
- NONDESRUCTIVE DETECTION up to 3/4-Inch deep using Electromagnetic field (EMF) technology
This Calculated Industries Duo Pro Pin & Pinless Moisture Meter is a pin and pinless meter in one. The pin function is good for pinpointing leaks and areas of water damage. It does require you to pierce the drywall to detect the amount of moisture. Pin moisture meters work by measuring the conductivity between the two prongs and can measure moisture levels accurately at different depths. They are more useful for finding problem areas- measuring the moisture content of a larger area is more time-consuming.
- ESTIMATE MOISTURE CONTENT QUICKLY AND EASILY – detector offers ideal dual functions of pin and pinless sensors in one. Use the pinless pad as a quick “ranging” feature to scan a large area for suspect areas without leaving holes. Then, switch to pins to quantify moisture level at various depths
- PERFECT FOR HOME INSPECTIONS – Use the pad for quick non-invasive pinless scanning to find locations with higher than average moisture behind a wall or under a floor. CAUTION: Powerful pinless pad sensor measures to ¾” but can be influenced by materials up to 2 inches below subject material (e.g., metal screws, nails, workbench supports, etc.) Keep fingers clear of pad scanning area. Use pad to detect variations from normal and use pins to quantify it.
- CHECK LUMBER AND HARDWOOD BEFORE BUILDING AND WOODWORKING – Use the pins to know the moisture content of your wood to make sure you’re not using damp, moist wood on your projects to avoid cracks, splits, warping. Ensure wood flooring has acclimated before installing
Relative Scale Measurements
While some moisture meters have modes that give a quantitative measurement of the moisture level in drywall, it’s more common in lower-end models to have a relative reading for non-wood materials. This isn’t necessarily a bad thing. Remember, when determining an acceptable moisture level in your drywall, relative humidity matters.
These relative scales measure moisture on a 0-100% scale where 0 is as dry as your baseline and 100 is completely saturated. You will need a piece of drywall or dry area you can be sure is not moisture-considered to take your baseline reading.
This method of taking comparative moisture levels in your drywall allows you to account for the humidity in the air and determine safe moisture content. It also allows you to monitor an area you suspect is damaged. Take several readings over some time. Most of these meters are at least very accurate at measuring relative moisture. If you notice an area is getting higher and higher reading of moisture, you know something is wrong. You can also monitor moisture readings after a flood to make sure things are drying out or determine when your drywall is dry enough to finish.
Water Damaged Drywall
When you’ve detected excess moisture – either a quantitative result that’s over 17%, a relative moisture content that’s significantly higher than the baseline in that area, or you can visually assess water-damaged drywall; you have to address it.
If your drywall is still under 17% moisture content, it could be saved. After prolonged exposure (over 72 hours) above 17% moisture, the drywall is unsalvagable, and you will have to replace it.
If it was just brief water contact, you can place a fan in front of the drywall and let it air out until the moisture levels go back to normal. Never cover or finish drywall if the moisture level is unacceptable.
If your moisture level was very high or visible moisture damage, there is a good chance you have a leak, and you’ll have to take care of that first. You can use your pin moisture meter to find the epicenter of the damage by finding out where the highest moisture level is. Remove the drywall and find the source of the water intrusion before you do anything else.
Depending on the severity of the damage, you may be able to use a simple drywall patching kit, or you might have to replace whole panels. Though water-damaged drywall isn’t as serious as damage to the structure of your house, it’s unattractive and could mold if you’re not careful. It’s always best to replace water-damaged drywall.
Maybe the problem lies behind the drywall. You can detect problems in the framing or beyond finished drywall with a pin-type moisture meter. If you’re checking the framing through the drywall, be aware that the mode your moisture meter is in should be a wood setting.
Checking the moisture level in your drywall is easy and a good way to make sure you are working with quality materials, aren’t experiencing leaking in your walls, and are maintaining a safe, mold-free space.
Look for moisture levels that are between 5 and 12%. Use a moisture meter with a drywall or gypsum setting, or take a relative measurement using a know dry area as your baseline measurement.
Replace any drywall over 17% or that has obvious stains or water damage.
Further reading: Our complete review of the best moisture meters for drywall.