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RedGard | Can It Be Used on Drywall?

If you’re doing any kind of home reconstruction, you know that while drywall is not the most long-lasting of building materials, it is extremely versatile and very affordable. This makes it desirable. However, it is essentially made of paper. Wouldn’t it be great if there was a simple, easy-as-painting option that would suddenly make using drywall almost everywhere an option?

RedGard is a liquid waterproofing membrane, which is painted onto surfaces, imbuing them with waterproof powers. In this article, we look at the theory, practice, and tips for using RedGard on drywall.

RedGard is not designed for use on drywall, yet many people have successfully done so. RedGard does not make drywall fit for use in wet areas. Additionally, if applied incorrectly, the RedGard will nort form a sufficinet barrier and if water get into the drywall, it is ruined.

Product is Designed for Use on Regular Drywall

Regular drywall is a man-made material made from gypsum plaster and paper and is extremely porous, easily taking in and holding moisture. This means that waterproofing it is beneficial.

RedGard is designed for use on regular drywall. You can see that it is included in their list of appropriate surfaces in the product information pamphlets

However, it is specified that it is only effective on regular drywall in dry, indoor areas. As RedGard (amazon link) is a liquid waterproofing membrane, it is possible for users to accidentally miss a small area or apply too thin a coat. This would allow for moisture to get in, ruining the drywall and surrounding construction. 

Obviously, this would be more of an issue in wet areas such as bathrooms (showers, especially) or moist basements.

Professionals Use RedGard on Drywall

Drywall was only included in the product information pamphlet as an appropriate surface for RedGard in July 2021. The pamphlet published a few months prior to this did not include drywall.

This meant that until recently, many people were divided over its effectiveness on this surface. However, many professionals have been using it on drywall successfully, even before the updated information came out. 

In the video below, one such professional shows the waterproof qualities of RedGard by waterproofing the interior of a box constructed from regular drywall and letting it sit full of water for over a week without any leakage. 

He also shows the correct application of RedGard, coating each of the walls with a roller brush before filling in the seams with a paintbrush and then repeating the process a second time. 

This process is demonstrated again in another video (below) with similar results, except this time, with over three weeks of water soaking time. 

Tips for Applying RedGard to Drywall

  • To use RedGard on normal drywall, make sure it is free of all drywall mud, paint, and other potential contaminants, and is completely dry. Contaminants and other imperfections weaken the bond between RedGard and drywall, creating possible entry points for water or other liquids. 
  • It is also important to consider the product description listed on your RedGard Tub where it explains areas RedGard and drywall can be used together, such as dry, exposed surfaces that are clean from contaminants that could prevent a good bond. 
  • Do not use RedGard on drywall in wet areas like showers or under drains, as even the smallest leak could lead to a ruined project. 
  • Dampen any porous surfaces and pre-coat the corners and anywhere floors and walls meet, in a continuous, even filming with overlapping strokes. 
  • Do not try to cover any joints or areas with expected movement
  • While RedGard recommends two layers for most applications, when using it on drywall, many find it useful to add a third layer with a paintbrush for seams and corners.
  • As demonstrated in the previous section, many professionals do use RedGard on drywall. But like them, you should conduct a test yourself to make sure RedGard is safe and effective for your specific project environment. 
    • One option is to conduct a similar “drawer” test, sealing your drywall in the shape of a small, open-faced box before waterproofing it with RedGard. 
    • After placing the box somewhere that can get wet in the case of failure, fill it with water and wait a few days to see if there are any leaks or damp areas.

Regular Drywall Must Not Be Used in a Bathroom

Regular drywall, for the most part, cannot be used in bathrooms, especially in wet areas, such as sinks or showers. 

Even if drywall is sealed in RedGard or other waterproofing membranes, the risk of failure and the impacts of wet drywall are potentially catastrophic. 

drywall not used in the bathroom

Not only does drywall fall apart when it gets wet, but it also retains moisture and creates an optimal habitat for mildew and other types of harmful molds. This is one of the reasons liquid waterproofing membranes are not approved for bathroom uses. 

In many states, using sheetrock/drywall for bathroom surfaces is against code. Even Greenboard, which is advertised as moisture-resistant drywall, is not suitable for tile backing or other bathroom uses as it also expands and swells with moisture and ruins any tile installed on top of it. 

Alternative Options for Bathrooms

Glass Mat Gypsum Wall Board and USG Purple are two drywall alternatives to regular drywall for bathroom use, but most contractors prefer cement backerboard instead. 

This is because cement backerboard offers a strong, water-resistant surface for shower tile or other finishing products. You won’t need to cover your entire bathroom, just the wet shower surfaces.

Other options are Fiber Cement Board and, ideally, Foam Tile Backer Boards. 

Both cement backerboards and fiber cement boards will need waterproofing products as well as mesh tape for their seams. But because Foam Tile Backer Boards are waterproof themselves, additional membranes are not necessary, leading to faster installation and a better-sealed product. 

They also have the added benefit of being lightweight and easy to cut compared to their cement board counterparts.

RedGard Can Be Used on Gypsum Drywall

Gypsum drywall is a bit different from regular “sheetrock” boards and is permitted for use with Regard. 

Gypsum is a naturally occurring mineral that is partially soluble in water, meaning it can create strong bonds with liquid waterproofing membranes such as RedGard. This is why it is listed as one of the many allowable areas of use for the product.

As long as the gypsum-based materials are clean and structurally sound with a minimum of 2000 psi compressive strength, RedGard can be properly applied. 

Start with a primer coat consisting of one part RedGard and four parts clean, cool water mixed in a clean pail, making sure to keep the surface wet for at least fifteen minutes. After drying you can apply your second coat of undiluted RedGard. 

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