Why replace wet drywall? There is a few reasons. I am talking about drywall that has soaked up the water and is saturated. Biggest problem becomes mold. Drywall needs to be dried or removed as quickly as possible to avoid mold growth.

Why replace wet drywall?

Wet drywall that has been wet to long, will soak up the water like a blotter. As a result the drywall can become soft or crumble damaging the texture. Wetter the walls, certainly the longer to get them dry causing mold. This is why you replace wet drywall.

While many companies will tell you that you can dry out drywall. With the use of special equipment and many different methods. I agree, you can save wet drywall if it only has light water damage. They also recommend removing baseboards to allow air behind the wall. This unfortunately does very little to help inside the wall.

Removal of baseboard, is not of much use, in allowing air behind the wall. Behind the baseboard you have the drywall, which may be raised a little off the floor. However the 2″x 4″ the drywall is attached to, goes all the way to the floor. It does not expose any openings for air to enter behind the wall. Then if there is insulation or cross beams in the wall it further blocks any air flow. Due to the fact the air flow will be blocked preventing proper drying time mold and mildew will form. Removal of baseboard is only helpful to the outside section of drywall directly behind the baseboard. Think of a wet rag in a sealed bottle with no airflow. For a better explanation see attached video and picture below.

Why replace wet drywall?

While the outside of the drywall gets an airflow and will dry fast. Inside the wall which is not painted, soaks up even more water than the outside. To make matters worst the wall is sealed and gets no airflow inside. Depending on code in your area most inside walls with drywall use 2″x 4″ studs placed 16 or 24 inches apart. There is a 2″ x 4″ stud across the top and one at the bottom with maybe a few cross members in between. Outside block walls will have 1″x 2: strips on the inside of the wall with insulation, then drywall is attached to that. The interior walls should also have insulation in between which will restrict any air flow and reduce sound. Each section between the beams are like sealed boxes.

Water inside the wall, will take a very long time to dry, because of the lack of air flow. That is what’s going to cause mold/mildew. Another potential problem, termites love wet wood.

Picture above is a wet rag in sealed bottle for 10 days with no air flow. It has been in the sun and in a air conditioned house and has not even begun to dry. Now do you believe the restoration companies when they say they can dry inside your walls? You can do this test yourself to back up may claims. Just put a wet rag in a bottle and seal it air tight.

Picture above is the same bottle, still sealed, and still wet, 10 months later

Water damaged walls must be dry before painting

How do you fix drywall that has water stains but is not soaked and damaged. Wet drywall, will leave stains. Using paint alone will allow stains to show through the paint. When dry you can use a stain blocker to cover and hide stains. A popular brand is Kilz, it is a very good stain blocker product. It comes in oil base and water base.

How do you cover water stains?

The water base Kilz, has a low odor which is great for indoor work.

Kilz oil base product is more suited for outside work as it has a very strong odor. Both products work very well. Apply by brush/roller or spray can, covering stains completely. Let dry completely before painting. See product ordering and details below.

What to do about wet drywall?

Most drywall with minor water damage is not a big problem. Just let it dry completely, then cover stains with a stain blocker like Kilz and paint.

While in contrast drywall with heavy damage requires removal of wet sections.

How can you check inside the wall for moisture and mold

There are many testing devices and methods available to test the walls. You can buy special water meters which will show moisture content. Because of water marks it will be obvious walls have been saturated. Walls with water marks a couple of feet up the wall is a tear out the drywall situation. Why waste time, the wet section should be removed before you get any mold to start with. However don’t tear out with out your adjuster being aware of the damage. You want to make sure you get pictures showing water stains and the damage.

If you check for mold as soon as it happens, there most likely would be no mold. Although mold can grow in just a few days, it can take longer for mold to grow.

When you discover drywall is already dry, but has mold.

Mold/mildew will first show up as black or dark spots, because that is a sign you already have a problem. Make plans to have that section replaced. If no mold/mildew, however there are signs the area had been wet. Cut a small hole, check in the hole with a mirror or shine a light in the hole or use a web cam. You not only may see mold, you will smell mold if it is there.

When the drywall has mold and mildew?

If it does have mold/mildew it needs to be cut out and replaced. Wear a mask, put any moldy pieces in trash bags right away. Do not carry loose pieces through the house.

How do you replace damaged drywall?

Cut 6 inches above damage area, then find the nearest vertical stud and cut the drywall to the center of the stud. That will give you a place to secure the drywall. On the top section you cut out, you may have to install a metal bracket to hold a cross beam. What that means is a piece of stud from one stud to the other. This will give you a place to attach the drywall patch. You must be able to secure the patch all the way around. Make sure your beam is flush with the existing beams.

Before closing patch

Vacuum with a good micro filter bag, inside the wall before closing. Seal and throw away vacuum bag. Purchase a good mold killer, most janitorial stores will have it. Spray mold killer on the beams in the wall and the back of wall. If you are having someone else do the work, check with your State. Some States require the contractor to be certified in mold removal.

How do you install the drywall?

First of all you need to purchase the drywall to replace the damaged section. Make sure you get the correct thickness, measure a dry piece. Wet drywall will swell causing an incorrect thickness measurement.

Cut drywall a few inches more than required, put it against the wall and mark around it. Cut on the mark you put on the wall. Drywall should fit snug in the cut out space. Using drywall screws attach drywall to beams, counter sink screws just a little.

How to apply tape and mud?

First apply drywall paste/mud to joints. Then run a 4″ flexible drywall putty knife over it to smooth it out. Make sure to overlap joint at least 2″ on either side. Apply tape with folded over center section against the joint.

Now cover the tape with the drywall paste, making sure the tape is wet and has no wrinkles. Once again run your 4″ flexible putty knife back over it , feathering it out on the edges. You don’t need the paste to be to thick, that will make it harder to smooth out later. Don’t forget to cover screws with the paste.

Let the paste dry 24 hours

Let paste dry 24 hours, because it will wipe away from joint if still wet when you attempt to smooth it out. After it is completely dry, Use a clean damp not wet sponge to smooth out the paste. You can also sand lightly with 150 grit sandpaper. Beware, sanding creates a lot of dust.

When you have finished blending in the paste, you will need to match the texture on your wall. The texture on your wall will determine what method you need to use to match it.

There are spray cans of texture mix you can purchase that may help. Another method is using drywall paste with a stiff brush, just dab it lightly on the wall matching the pattern of wall. There are also quick drying drywall paste you can use.   

Hope this answers any questions about why you should replace wet drywall

Visit my YouTube channel for helpful videos

Read my post on prevention tips. If you follow my prevention tips you can eliminate some of the causes of water damage.

This is a very good YouTube video by Reno Vision DIY on taping drywall.