KERDI boards are among the most popular building materials. These multifunctional panels can be used as floor or wall tile substrates – especially in wet areas – or as building panels.
Contractors often install them in showers or bathrooms, where they are usually tiled. But what if you want to use them as side panels without tiles?
KERDI boards can be painted on. However, you must plaster the surface first or cover it with a spackling compound. Panel edges must also be reinforced and covered with a trowel-applied material. Sand the surface when you’re done, prime, and apply the preferred latex or specialty interior paint.
Painting KERDI Board In 6 Steps
KERDI boards are manufactured by the German brand Schlüter and are among the most commonly used tile substrates in the world.
In the USA, they represent an alternative to drywall or Wedi panels in wet areas, such as bathrooms, mudrooms, and shower stalls.
While these boards are intended as a substrate for tiles, Schlüter confirms that they can be painted if covered with plaster or a spackling compound.
Things You’ll Need:
- Plaster or spackling compound
- Reinforcement adhesive tape (KERDI-Board-ZSA)
- Tile adhesive (optional)
- Plastering trowel
- Plasterer’s hawk board (optional)
- Bucket trowel (optional)
- Power mixer
1. Skim The KERDI Boards With Tile Adhesive
KERDI boards are designed for tile installation, and their surface adheres best to tile adhesive.
Even though Schlüter doesn’t require treating the boards with tile adhesive before preparing them for painting, DIYers and contractors found that skimming the boards with adhesive before plastering improves results.
You can use any tile adhesive for the job.
So, if you want to create a partially tiled and partially painted wall, you can skim the entire surface with the adhesive. Let it dry, then install the tiles (if needed) before proceeding with the steps below on the exposed surfaces.
2. Reinforce The Edges
A crucial step when painting over KERDI boards is that of reinforcing any exposed edges. This step is essential because, without tile, you can’t caulk the edges or protect them with a tile finishing strip.
Without protection, the boards can start to crumble over time – these boards are made of cement and sand and can degrade if exposed.
The easiest way to protect any edges is by covering them with reinforcement adhesive tape designed for joints and seams between the panels.
While you can use any brand, the KERDI-Board-ZSA is a good example of adhesive tape you should use.
Start from the top and apply the tape all the way to the tile or floor. Run your fingers over it and press it to ensure proper adhesion.
3. Mud The KERDI Installation
When painting KERDI boards, the skimming step only serves to improve the adhesion of plaster or spackling compound to the substrate.
However, you must plaster the surface or cover it with a spackling compound. This filler should go on the entire surface, including the taped edges.
Prepare the plaster or spackling compound by mixing the powder with the right amount of water – refer to the product label for quantities.
You can mix by hand, but using a power mixer is recommended to obtain a smooth paste.
If you decide to use a plasterer’s hawk board and a bucket trowel, use the trowel to load the hawk board with the mixture, then scoop a dollop of plaster and spread it on the wall with a plastering trowel (a metal trowel with no notches).
For the best results, you must plaster any joints between boards first. Let the compound dry and even it out with sandpaper.
Working on small sections at a time, apply the first plaster layer to the entire surface. Try to even out the compound with the trowel as much as possible before moving to the next section. Let it dry and sand it out.
Repeat the process and let the final plaster layer dry out. Wait for it to cure as instructed on the label.
4. Smooth Out The Surface
For a top-notch painting job, it is essential to smooth out the surface before coating it. This is especially true for gloss or satin paints that highlight most imperfections.
Matte paint tends to mask imperfections, but deep ridges or bumps can be visible under the paint.
Use medium sandpaper and a sander to remove the most visible bumps, ridges, or joint lines. Then, sand the entire surface with a fine-grit sandpaper. Don’t apply too much pressure.
Wipe the surface with a slightly damp cloth to remove the dust, then let it dry for at least 24 hours.
5. Prime The KERDI Board
The KERDI boards are now prepared for painting; however, not all paint types adhere properly to plaster.
If your coating doesn’t bond, it can peel off or flake in time. Special paint types, such as anti-mold paints, might also fail to work as intended if they don’t bond with the substrate.
To prevent issues, it is best to prime the surface first.
Always match the primer with the type of paint you want to use. Latex paints are the most commonly used due to the low concentration of volatile organic compounds.
However, some bathroom or kitchen paints could contain solvents and may require a specific primer type.
If unsure, check the label on your paint tub.
Start from one corner and apply a thin layer of primer with a paintbrush. Work your way across the entire surface and let the primer dry and cure as instructed – typically between 24 and 48 hours, depending on the type.
If you want to paint with a latex product and don’t want to use primer, you can prepare the surface with diluted paint (5-30% water).
6. Paint The Substrate
Once the primer is dry, sand the surface once more with fine-grit sandpaper to remove any paint brush strokes.
Wipe off the dust, then apply the paint with a paintbrush or roller. Let it touch-dry (around two to four hours for latex paint), then apply a second coat.
Let the paint dry and cure for 24 to 48 hours before hanging anything on the wall.
KERDI boards are designed to be used as a substrate for tiles. However, you can finish any exposed portions with paint – or even paint the entire panel if you want to use these boards instead of drywall in higher moisture areas such as a mudroom or kitchen.
However, before coating them with the desired product, you must plaster the surface and prime it to make sure the paint won’t peel or flake.