How To Waterproof Drywall In A Garage? (3 Effective Ways!)

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How To Waterproof Drywall in a Garage?

Drywall is cheap, fire resistant and easy to install. Not surprisingly, drywall is the most popular sheathing board for garage interiors. However, drywall has its flaws; poor water resistance and impact resistance. So, how to waterproof drywall in a garage?

Many manufacturers offer mold resistant drywall. You can waterproof ordinary drywall in your garage by applying waterproof primer and paint. Alternatively, you can use waterproof panels to protect the drywall bottom or the entire drywall.

In this post I will explain about each of the three ways in which you can have waterproof drywall in your garage.

1. Use Mold Resistant Drywall

Drywall is basically a panel of gypsum held together by additives and sandwiched between two sheets of paper.

Gypsum is solid, powdery, porous and highly hygroscopic. Drywall absorbs water like a bath towel. Water on the garage floor will wick and spread up the drywall, making a large section of the lower drywall wall soggy.

A wet and soggy drywall will promote the growth of mold & mildew. Wet drywall loses structural integrity and is likely to crumble and collapse at slightest impact or load.

There is a difference between waterproof and moisture resistance. Waterproof implies that the product is completely impervious to water. Moisture resistance implies a low level of protection against moisture.

There are no waterproof drywalls in the market, only moisture resistant.

The two products that are pretty good are:

Sheetrock® Brand Mold Tough® AR Firecode® X Panels

5/8 in. (15.9 mm) Type X panels with abuse, moisture and mold resistance

Performance	Mold & Mildew Resistance, Abuse Resistance
Edge	Square Edge; Tapered Edge
Thickness	5/8 in.
Width	48 in.
UL Type Designations	AR

PURPLE XP® Drywall

Purple drywall manufactures a line of drywall that is moisture-, mold- and mildew-resistant and ideal for application in the garage. The products offered by the company are:

Product Name	Outstanding Feature
PURPLE XP® Drywall	Versatile, moisture-, mold- and mildew-resistant.
PURPLE XP® Hi-Abuse® Drywall	Moisture-, mold- and mildew-resistant, enhanced protection against scratches and scuffs in high-traffic areas.
PURPLE XP® Hi-Impact® Drywall	Combines moisture-, mold- and mildew-resistance with added protection against accidental holes.

Purple Drywall is available at Lowe’s and other outlets.

2. Apply Waterproof Primer & Paint to Drywall?

Applying waterproof primer and paint to the drywall in the garage is no different than applying regular primer and paint to the drywall. The difference is only in the products used. The three basic steps are:

Prepare the Drywall for Painting

Once you have installed the drywall you have to make sure the surface is smooth for priming. Fill out nail or screw holes with patching compound. For larger dents, holes and joints use a good quality joint compound (drywall mud).

Patch up areas with large holes or cuts using stick-on mesh patches. For joints and corners use Drywall Joint Tape-13 MESH,100% Fiberglass, Heavy-Duty Self-Adhesive Wall Crack and Seam Patch.

I recommend using USG Ez Sand 90 Joint Compound as it gives you a 90 minute window to complete the job. The compound is lightweight for easy handling and sands easily for fast, smooth finishing.

Every time you apply drywall mud to a joint, you need to lightly sand the wall after it dries. Do it till the surface is as smooth as possible. 

Apply a coat of Moisture Resistant Primer

Next apply a coat of Moisture Resistant Drywall Primer. The choice of the right primer is important. The primer needs to have good adhesion properties along with high moisture resistance. I highly recommend using

Zinsser Perma-Guard Water-Based Mold and Mildew-Proof Clear Sealer

Apply two coats of Moisture Resistant Paint

You need to apply at least 2 coats of the top coat to get a uniform smooth finish. You just can not get the richness in the finished color with one coat. I highly recommend

Zinsser Perma-White Mold and Mildew-Proof Interior Paint

3. Cover Drywall with Water Impervious Panels

Waterproof or rather moisture resistant drywall basically uses waxy paper to shield the gypsum from moisture. Great idea, but what happens when the drywall is cut. The gypsum is exposed. There is no waxy paper to prevent water from reaching the gypsum.

The drywall wall, in the garage, mostly gets wet from the water pooling on the floor. Garage floors can get wet easily for a variety of reasons such as snow melt, car washing, etc. 

If you can protect just the bottom of the drywall from water, then you would have met your objective. 

Installing a garage floor trim is an easy and affordable way to protect the water on the floor from coming in contact with the drywall. The caveat is that the water level should not be too high. Floor trims are usually only 2 ½ ”, 4” or 6” high.

Garage Floor Trim are available in following waterproof materials:

• Thermoplastic Vinyl (TV)
• Thermoplastic Rubber (TR)
• Thermosetting Rubber (TS)

If you expect the water level to be higher or are worried about water sprays or splashes then you should consider using garage wainscoting panels. Wainscoting only covers the bottom part, usually 1/3rd of the height of the wall.

Wainscot panels could be made of any material including wood, engineered wood (e.g. MDF), polymers (e.g. PVC) or metal (e.g. aluminum diamond plate). Choose a waterproof panel such as PVC or metal.

If you are looking for a stunning macho look for your garage décor, take a look at the 3’x8′ Set of Anodized Blue, Black and Polished Diamond Plate Tiles from CarGuyGarage, which are designed for use as garage wainscot panels.

Thank you very much for reading the post. I do hope you found it informative and useful.