Plastering over cement board is possible. But it requires thorough preparation and the use of other products for it to hold. It’s a project that professionals can best pull off.
But if you are new to this, we recommend adding a blueboard to the cement board and then plastering it.
If you are planning to plaster over cement board, this article will go through the various options you may have, and we will recommend whether it’s something worth trying.
How Do I Get Plaster to Adhere Over Cement Board?
The biggest issue with applying plaster over cement board is it won’t adhere. Quite often, it will start to peel off. If you must pull off such a task, you will need to use a quality primer.
A good example is Plaster-Weld. This product will give the plaster a base to adhere to. That’s not all. You will also require a handful of plaster mixed with sand. The purpose of the sand is also to promote adhesion.
You should apply at least two coats, then give it time to dry. If done correctly, the plaster should adhere to the cement board. You will know you have succeeded after two days since that’s where the peeling is most likely going to occur.
A primer plays a critical role in this scenario. Therefore, even if you don’t find plaster weld in a store near you, ask for recommendations for another quality primer. Do not be surprised when the guys at the store ask you to switch to a blueboard.
What is a Cement Board?
Even before we go further on whether it’s possible to plaster over a cement board, we must learn as much as we can about what a cement board is. This information will make it easier for you to understand why you can or can’t plaster over it.
These are sheets that are made out of fibers comprising cellulose and cement. These boards can either be a half-inch or quarter-inch thick. They are mostly used as a backing for tiles.
Unlike paper-covered gypsum, a cement board is much stronger and resistant to water and moisture. Using a cement board as a backing is a great idea since it will help counter mold development.
Considering that tiles are mostly used in bathrooms and kitchens, this feature of a cement board is quite beneficial.
A cement board isn’t the lightest material to carry. It needs at least two people to move it around. It’s also quite dusty.
There are various places where cement boards can be used. Examples include kitchen countertops or a wood floor. Also, a cement board works well with stucco. Depending on your project, you can install a cement board outdoors or indoors.
Regarding installing a cement board, you will need first to layer a vapor barrier and then an adhesive. The board should then be attached using drywall screws.
Will Stucco Help Plaster Adhere to Cement Board?
On various forums, there are recommendations about using stucco to create a surface for the plaster to adhere over a cement board. If you have also come across such recommendations, you may be wondering if they can work. Let’s find out.
Stucco is a popular product in the building industry. It’s a product that can be used on walls or surfaces such as cement boards to give it a textured and colored finish.
Stucco is made for outdoor and indoor use. The outdoor option is built to withstand UV rays and other elements. Generally, stucco is a cement-based siding made using lime, water, sand, and cement.
Stucco is available in a wide range of colors and finishes. There is a cement and acrylic finish. We won’t get much into the types of finishes stucco offers since our goal is here to plaster over it after it has been applied to a cement board.
When it comes to using stucco on a cement board, the goal is to prolong and beautify the surface of the cement board. You can do so if you want to plaster it, but you won’t get a much better finish than the stucco.
Stucco can create the ideal surface for you to plaster over a cement board. Before plastering, the stucco will need to go first. Here is a quick rundown on installing stucco over a cement board.
First, you will need to estimate the cement board surface covered by stucco. You can use a tape measure to get an accurate figure. You will need sheets of fiberglass reinforcing mesh to ensure the board has a uniform surface area.
The sheets can be overlapped on the cement board for better results. Don’t forget to place the mesh on the joints of the cement board.
Once that’s done, you will need to introduce a bonding agent. This should be brushed over the mesh and cement board. It should be given time to dry before stucco is introduced.
Stucco should be applied carefully. It should be about a quarter-inches thick. You can use a trowel for the application. Give the first layer some time to harden before scratching over it with a plasterer’s comb.
The goal of the latter is to reduce the layer to about an eight-inches thick. Give the finished surface around two days to harden while spraying it with some water.
You can add a second layer of stucco to cover the scratches you created above. The second layer should be a quarter-inches thick. The second is usually the last layer. Therefore you can create the finish that you want.
Can I Plaster Over Cement Board on an Area that Won’t Be Tiled?
When defining a cement board, we mentioned that it acts as a base layer for tiles. If you have a cement board and don’t want to install a tile, is it okay to plaster it?
Similar to what we have described above, plastering over cement board brings about adhesion issues. The plaster will come off after a few days.
So far, we have gone through two methods. The first is using a wall primer, and the other one is applying stucco.
The above aren’t the only methods to help you plaster over a cement board. There is another option that requires the use of metal lath.
You have to install a metal lath followed by two or three coats of plaster. Using an adequate amount of plaster is crucial to ensure it sticks firmly to the metal lath.
The other option you can use to plaster over a cement board is hanging a blueboard and plastering directly over it.
Unlike cement board, a blueboard is much easier to plaster, and it doesn’t have most issues that a cement board has.
As mentioned in the beginning, if you must plaster a cement board, look for a blueboard to act as an intermediary. Blueboards can be found in most hardware stores.
Can I Plaster Cement Board in the Bathroom?
If you are installing tiles in your bathroom and want to create a finish whereby the tiles only reach a certain area and the rest is left exposed, you will need to do something about the cement board.
Plastering within the bathroom isn’t recommended because of moisture and condensation. It’s advisable to tile to the top than leaving a cement board exposed.
However, if you must plaster the cement board in the bathroom, we have shared some methods you can use. Installing a metal lath seems to be ideal for this particular scenario.
Is It Worth Plastering Over Cement Board?
Plastering over walls has been a common method of creating a smooth and decent finish. However, plastering doesn’t always come out flawlessly on surfaces such as cement boards.
Quite often, the plaster won’t adhere unless it is forced to bond with something else, such as a primer, stucco, or metal lath.
Out of the three, a primer is the most convenient to use. You will need to research the types of primer you can use to stick plaster to the cement board.
Regarding stucco, we have already mentioned that it creates a decent finish on its own. Therefore, it wouldn’t make much sense for you to apply stucco and then cover it with plaster. The metal lath can also deliver good results.
The bottom line is that plastering over cement board is more of a trial-and-error project. You can easily pull this off if you possess some quality building skills.
However, if you are just getting started, we advise you to get a blueboard, add it to the cement board, and then plaster it.
This will be much easier, and there is a higher chance of the plaster holding onto the cement board for much longer.
At the end of the day, whichever method you use, something will need to be between the cement board and the plaster. You can’t go directly into applying plaster over a cement board.