You can do many things to an MDF board, but plastering isn’t one of them. The material of an MDF board doesn’t offer adequate grip for the plaster to adhere to.
Therefore, when you plaster over an MDF board, it will eventually fall off, and the repairs will be very costly, especially if you had already painted over the plaster. It doesn’t matter what your reasons are. Plastering over an MDF board isn’t a good idea.
What If I Apply Primer First?
Primer is an excellent adhesive binder. Therefore, you may be tempted to prime and then plaster over MDF. Primer won’t be of any help in this scenario.
Because the plaster will fall off later or even during the application process. Therefore, the simple answer to whether you can plaster over the MDF board is no.
Why Can’t You Plaster Over MDF Board?
The reason why you can’t plaster over the MDF board is that this surface is very porous. The water or moisture in the plaster will be absorbed by the MDF board leaving behind sand and cement.
It’s why plaster doesn’t last for very long over the MDF board. The plaster automatically disconnects itself from the MDF board, even if applied thickly.
Is There a Hack on How to Plaster Over MDF Board?
In the construction industry, there is always a loophole. Yes, the plaster won’t adhere to the MDF board. But there is a way to make it work, and it’s by using an expanded metal lathing.
Abbreviated as EML, this material comprises a diamond-shaped mesh that acts as a holding base for the plaster.
Before plastering the MDF board, you must cut some EML and attach it to the surface. Please note that MDF is not waterproof.
Therefore, it’s crucial to add a moisture barrier that will prevent the MDF board from swelling because of the water that will be present in the plaster.
Anyway, attaching an expanded metal lath using nails or screws will offer some texture for the plaster to stick to. This is the best method of plastering over the MDF board that guarantees lasting results.
What If You Scuff Up the MDF Board Surface?
If you are determined to plaster over the MDF board, you may consider scuffing up the surface to create a textured surface for the plaster to stick to.
Even though this may temporarily work, rarely will plaster hold onto a naked MDF board. Therefore, it will fall off after some time.
The only way you may make plaster stick to an MDF board is by making holes in the MDF board.
The goal would be to get the plaster to hold to the substrate behind the MDF board. There is no guarantee that this will offer long-term results. Also, you will be damaging the MDF board.
The best advice we will offer you here is to buy some metal lath. This cheap material is widely available in most stores near you.
It’s very easy to use because all you need are some screws and nails to hold it onto the MDF board.
Scuffing up the MDF board isn’t recommended by expert builders. If you want long-lasting results when you plaster over the MDF board, you should use a metal lath.
What Happens When You Plaster an MDF Board?
As you already know, there is water in the plaster. MDF boards being a composite that contains wood fibers mixed with resin, will absorb the water from the plaster.
When that happens, the MDF board will swell, and, in the process, the plaster will be disconnected from the surface. In one way, the swelling will push the plaster from the surface of the MDF.
Should I Replace MDF with Plasterboard?
Another way to save yourself the trouble and losses of plastering over MDF is to replace the latter with plasterboard. MDF wasn’t designed to be plastered.
However, that’s the primary job of plasterboard. If you are renovating your home and there is an area with an MDF board, and you would like to smoothen the surface, you should replace it with plasterboard.
Understandably, not many homeowners will be enthusiastic about discarding MDF boards that are in great shape.
But plasterboard is your safest bet if you intend to plaster over the surface. The plasterboard will adhere for years without coming off.
Replacing MDF with a plasterboard is even better than using a metal lath between the MDF and plaster.
Can PVA Primer Help in Plastering Over MDF?
If you have used PVA primer before, you can testify to how effective it is at sealing the pores of drywall. As effective as PVA primer is, it will not help plaster bond to MDF.
It may work for a short duration, but the plaster will fall off, and you will either have to use a metal lath or replace the MDF with a plasterboard.
Will Polished Plaster Stick to MDF?
These days, we have polished plaster, a relatively new product that can be applied on a wide range of surfaces. On your quest to find out whether you can plaster over MDF, you may come across polished plasters made of crushed marble, lime putty, and other ingredients.
According to the manufacturers of polished plasters, it is alleged that these products can stick to MDF without cracking or falling off.
If you come across polished plasters, it’s important to approach such products cautiously because they haven’t been adequately experimented on.
Therefore, the results could either be terrific or disappointing. As long as the plaster contains water, you should be reluctant to put it over an MDF because it will cause the board to swell and expel the plaster.
You will need to perform thorough research before using polished plaster. Otherwise, it can significantly mess up your home improvement project.
How Long Will Plaster Last Over MDF?
If applied directly, then it won’t last for very long. However, the plaster will last for years if there is a metal lath or plasterboard. If the application is done well, it may not even crack at any point in the future.
When you apply plaster directly over MDF, it can start to fall off even before you are done. It will be an absolute nightmare if the plaster begins to fall off after you have even painted over the plastered MDF board.
We can’t emphasize enough the importance of not applying plaster directly to the MDF board.
Can You Plaster Over the Moisture-Resistant MDF Board?
Phrases such as moisture resistance can be quite misleading in certain situations. There are moisture-resistant MDF boards, and they are an excellent choice for use in kitchens or bathroom cabinets.
Please note that moisture resistance doesn’t mean waterproof. You can’t spray moisture-resistant MDF board with water and expect it to retain its shape.
Whether an MDF board is moisture resistant or not, exposure to water is a problem. Therefore, when you layer plaster over MDF, the water will pass through the holes in the board and make it swell.
The other thing is that the surface of an MDF board doesn’t have an adequate grip for the plaster to stick to.
What Surfaces Can You Plaster Over?
From the above, it’s evident that the MDF board isn’t a conducive surface to plaster over. So, which surfaces can you plaster over without any complications?
First, in line, we have plasterboard. It is the ideal surface to be plastered on. However, to ensure the plaster adheres for longer, you need to apply thin coats of plaster.
Besides plasterboard, you can plaster over old plaster, paint, brick, breeze block, and a wide range of surfaces. Before engaging in any plastering job, you need to confirm whether that surface is ideal.
For instance, in this case, if you were to plaster over MDF without researching first, the results wouldn’t be so pleasant.
Will Plaster Adhere to MDF on Its Own?
Not really. The plaster will never adhere to MDF on its own. Even though polished plasters promise better results, it’s essential always to use the recommended method in any home improvement project.
For plaster to adhere to wood, you will need to add a metal lath to help the plaster stick. The metal lath has to be bonded to the MDF using nails.
You can’t simply layer the metal lath over MDF and hope it sticks. Before beginning such a project, it’s crucial to have a bonding agent, which in this case is a metal lath.
Is MDF a Substitute for Drywall?
There are plenty of reasons why MDF isn’t a suitable replacement for drywall. First, unlike drywall, you can’t plaster over it with ease. Let’s assume you have an entire wall fitted with an MDF board.
Can you imagine how hectic it would be to plaster over it using metal lath? Secondly, MDF boards aren’t very big fans of moisture.
Continuous exposure to water will cause the MDF to swell and push the plaster and paint from the surface. You can’t substitute drywall with MDF.