It is a common misconception that mold, mildew, and moisture in the house where it should not be in general should be fairly easy to spot. However, when it comes to drywall, that is truly not the case. The super-absorbent consistency of drywall means that you could have moisture raining down between your walls for months without knowing a thing. If you have sneaky suspicions that there is water hiding out behind your walls, it is best to find out of your inklings are true as quickly as possible. There are a few professional-worthy tips you can use to determine if there is indeed moisture hiding out behind your drywall.
Check out the baseboards where the drywall meets the floor.
Drywall can essentially act like a wick if your roof is leaking and moisture is managing to travel in behind a wall. The water will seep into the drywall at the top, but because paint on the exterior will keep the moisture sealed inside, the moisture will bleed its way all the way down to the bottom of the sheet of drywall where it can finally make an exit. For this reason, hidden water behind drywalled walls will often make its first appearance along the floor or around the baseboards. Take a good look along the bottom of the walls around the trim and see if you spot signs of mold, mildew, discoloration, or even moisture. If you find any of these things, it is a surefire sign that you do have a moisture problem in your walls.
Test the density of your drywall with a series of knocks.
Moisture content will mean a different sound than usual when you knock on the wall. The knock will sound much more lower in tone, less sharp, and perhaps dull like a soft thud. Moisture content will absorb sound vibrations, which means a completely different sound. So even if the wall looks the same as usual from your side, a simple knocking test could help you track down hidden moisture.
Pull out your drill and cut a sample hole.
Grab piece of cardboard and your drill with a small hole-drilling bit attached. Lay the piece of cardboard directly beneath where you intend to drill a hole to catch any particles that come from the drilling action. Drill a small hole into the wall carefully without applying a great deal of pressure. Slowly pull the bit back out toward you after making the hole, allowing the drywall material to fall on the cardboard. Examine the drywall material that comes out with the drill for moisture. Because of the chalky makeup of drywall, it will be fairly easy to see if you have moisture problems because the normally fine particles will clump together.
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