Is your paint peeling off new plaster after you’ve applied a mist coat? You’ve come to the right place! With years of professional experience as a decorator, I’ve seen (and rectified) this problem numerous times.
With that in mind, today we’re going to be looking at the reason your paint is peeling off new plaster even after you’ve applied a mist coat. Furthermore, we’ll tell you what you can do to ensure your paint adheres properly next time. Sounds good? Great. Let’s jump in.
Reasons Why Your Paint Is Peeling Off New Plaster Even After Mist Coat
In my experience, peeling paint off new plaster is typically caused by 1 out of 5 possible culprits.
Using the Wrong Mist Coat Ratio
Maybe you searched the web for ‘the best mist coat ratio‘ and during your research thought you found the perfect ratio. This is your first error. You should always follow the manufacturer’s guidelines when it comes to mist coat ratios as different paints have different viscosities (or resistance to flow). If you’ve followed someone else’s advice then your paint might’ve still been too thick to use as a mist coat.
So what happens if the mist coat is too thick? It struggles to absorb into the new plaster and it will peel off after it dries as it has nothing to adhere to. When you apply your top coats to the mist coat, your whole paint system will peel.
Don’t know what mist coat to use? Simply reach out to the manufacturer and they will tell you. Better safe than sorry!
Using the Wrong Paint for Your Mist Coat
Another candidate for the cause of your peeling paint is that you might have used the wrong paint for your mist coat. There are a lot of recommendations out there from DIYers and old-school professional decorators alike advocating for the use of contract matt as a mist coat.
Whilst this used to be the go-to, the contract matts of today’s market are terrible at bonding with chalky surfaces and thus should be avoided at all costs.
When choosing a paint for your mist coat, make sure you get your hands on some vinyl matt, thinned to the manufacturer’s recommendation.
The Plaster Hasn’t Fully Dried Out
Another issue I come across often is when a client has attempted to paint before the actual plaster has had time to fully dry.
Plaster can take a minimum of 4 weeks to dry (and in many cases, depending on environmental factors, even longer) so if you’ve applied your mist coat and top coats before the plaster has had a chance to dry, there’s a good chance you’ve trapped plenty of moisture under your paint film.
And what happens to that moisture? Naturally, it tries to escape, and in the process lifts the paint from the substrate which results in peeling or flaking.
Applying Your Topcoats Too Soon After the Mist Coat
I’ve seen this one quite a few times. The client applied the mist coat perfectly and in their haste, threw a couple of coats of paint on before the mist coat had a chance to fully dry.
It’s recommended to wait at least a day before painting over a mist coat so if you applied your top coats before this, then you’ve found the likely cause of your peeling problems.
The whole point of the mist coat is that it absorbs and dries into the porous plaster, filling any microscopic holes. Once fully dried, it gives the top coats plenty to adhere to. However, if the mist coat isn’t fully dried then you run the risk of combining the two and ultimately reducing the capability of the paint to adhere to the substrate.
My top tip here is to just be patient.
Damp or Moisture Problems
If your home has problems with moisture or damp, then paint can peel off from the surface whether it’s new plaster or old plaster.
Whilst your mist coat and top coats are in the process of drying, moisture can get trapped underneath and as we mentioned above, will eventually try to escape and thus lift the paint film from the surface in the process.
How to Fix Peeling Paint On New Plaster
So now you’ve (likely) identified the problem, I’m going to give you some tips to rectify it. Bear in mind that peeling paint can be a messy and time-consuming job so sometimes it’s simply better to get the professionals in to deal with it.
If you’re not deterred then here is a solution to the problems listed above.
- Remove the peeling paint from the surface. If it’s particularly bad, remove the entire coat.
- Sand down the surface, preferably with a dustless sander.
- If you don’t use a dustless sander, dust down the surface.
- Apply a coat of Zinsser Gardz primer.
- Apply your top coats.
The Gardz primer is the key stage here. Gardz seals porous surfaces and will give your top coats something to adhere to.
You can use the above method to fix peeling paint on new plaster however if you have damp or moisture issues, the solution isn’t as clear cut.
First and foremost, you will need to get to the root of your damp or moisture problems. If you don’t remedy the underlying condition then the peeling paint is going to return. My advice would be to get a professional in for this stage. As a decorator with over 20 years of experience, even I shy away from attempting to fix problems caused by damp.
Once you’re free from damp, you can simply follow the method above.