One of the biggest problems with plastering is preparing walls for plastering. You could be the best plasterer in the world but if nothing is prepped then you’re in for a world of trouble!
There’s a very common saying that I’m sure you’ve heard: failing to prepare is preparing to fail! It’s the same case when you’re plastering. You need to make sure everything is prepped correctly! If not, you’re exposing your self to a lot of danger in plastering.
But don’t worry, we have you covered! We’ll give you the best advice in preparing your walls for plastering.
We’re going to show you the RIGHT way to do the job!
You’ll learn the whole process and we’ll even show you the materials you’ll need to get the job done. However, there are a few subjects we have to cover before you start:
High Suction/ Low Suction
When you plaster onto a wall you need to check the walls for suction. You’re probably thinking what does that mean and why does it mater? It’s a really important subject that means the difference between a hard and easy day.
All walls, whether its bricks or plasterboard, have a degree of suction. For example, bricks have a really high level of suction whereas plasterboard is really low. Learning to control this suction is what you need to learn. This is one of the key principles to mastering plastering.
When you use finish plaster the water in the mix gets drawn from the walls as it dries. Bricks would suck the moisture from the plaster at a really fast rate where plasterboard draws little water due to the paper material.
It simply isn’t as porous!
If you plaster onto a high suction background it gives you little time to get a lovely finish. This is why we need to control the rate of suction.
It gives you more time to get the plaster perfect which makes your life nice and easy!
Preparing walls for plastering
Let’s say you have a wall in your house you want to plaster. You need to strip all the wallpaper and make sure the wall is clear; but then what? You need to follow this routine:
- Strip Wallpaper
- Wash the walls down
- Check your walls
- Skrim tape any cracks
- PVA/ Blue Grit
We have a list of everything you need to do but you can save this article if it’s easier. This way you’ll have everything you need for when you’re ready to start!
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Let’s get to it:
1) Strip Wallpaper
You need to strip all the wallpaper and make sure the wall is completely clear of paper, (and I mean CLEAR) . If you plaster onto paper then it will peel from the wall and take your plaster with it!
This means all your hard work ends up on the floor! Make sure you get it all off. You don’t want any hidden problems because of a bit of wallpaper.
2) Wash The Walls Down
This process will remove any unwanted grease or grime on your walls which could potentially affect the plaster. I’ll show you what I mean with a little a story where it went horribly wrong:
We re-plastered an old ceiling once which looked fine. I didn’t wash the surface down because it looked OK. However, when I was plastering, I noticed that a few areas were sagging when I was applying the finish plaster. I didn’t think much of it so I carried on plastering.
I finished the ceiling and it all looked good. Mission accomplished!
I had to go back to the job a day later.
It was then that I realised a huge bubble in the finished plaster. I don’t mean a little bulb, there was a huge dome of dried plaster in the centre of the ceiling! When I looked closer I also saw lots of tiny cracks!
I inspected the plaster and realised that it had pulled away from the existing paint. 5 minutes later the whole lot was on the floor! There was a layer of hidden grease and the plaster didn’t adhere to the previous surface.
I learned my lesson the hard way!
You can’t always see problems on the walls so it’s always good to give your walls a wash with sugar soap. It cleans the walls ready for the next step in preparing walls for plastering. Also, check out this article on plastering onto paint because it shows you the RIGHT way to do it because it’s not always ok!
3) Check Your Walls
The first thing you need to do is check for any loose plaster. If there are any areas that are cracking or peeling make sure you scrape it off. If you plaster onto an unstable wall then the plaster will never hold.
You need to check to see if the previous coat of plaster is solid – we can’t plaster onto a wall that is “drummy” or unstable! If you tap the walls you can hear when plaster is solid to the brick. You need to make sure it doesn’t move, doesn’t sound hollow and definitely doesn’t fall away with pressure.
The other thing to check is cracks. Cracks are a sign of weakness on your walls so tap around any areas that seem unstable. If any sections sound hollow or seem to move then you need to hack the old plaster off.
You can’t leave it. It will cause way too many problems further down the line. It’s a pain but it isn’t worth it!
If some areas need to be hacked back then you will have to fill that with Bonding. I use British Gypsums Bonding which is an undercoat plaster. It’s a brilliant product which can be used onto brickwork, masonry backgrounds and many high suction backgrounds.
(If you have smaller holes I’d just use some filler before you start skimming. It’s a lot easier!)
You should also unscrew your light switches and plug sockets from the wall. This prevents you from getting plaster onto your electrics. I like to place them safely in plastic bags so no falling plaster hits your plug sockets.
Sometimes it’s actually easier to start again when preparing walls for plastering. If the walls are bad, you can stick fresh plasterboard to a bad wall providing you with the best background to plaster onto. If this sounds like an option then check out this article on applying plasterboard to a wall, (also known as Dot & Dab).
This just makes your life a lot easier when plastering which is what we all want isn’t it? Once you have everything cleared and you have a solid wall with no loose materials your good for the next part.
4) Skrim Tape
Once you have your walls scraped and clear you to need to prevent any problems returning. You might see a few cracks on your walls which could mean trouble in the future. If that’s the case, you need to apply scrim tape where the cracks are showing.
Its basically a mesh that sticks directly onto your walls and we do this because if there is any movement it keeps the plaster intact and prevents any cracks appearing onto your finished walls. It’s a really good product that allows for any natural movement in your home.
When your plastering on an existing wall you need to make sure you control the rate of suction and the best way of doing this is to paint or roll your walls with PVA glue. But why do we do this?
The PVA acts as a primer. It’s only really used to stop the plaster drying too quickly which prevents the walls from drawing all the moisture from your plaster. This reduces the rate of suction and gives you more time to get that perfect finish.
You should always mix the PVA with water. The instructions are found on the tub but I like to use 3 parts water with 1 part PVA. To be honest, I find some PVA really weak so I have used 2 parts water to 1 part PVA previously.
You simply paint or roll the PVA straight to your walls. You might sometimes need 2 coats. If your plastering over Artex, for example, I PVA the ceilings with 2 coat because Artex has a very high rate of suction.
The double coat increases the efficiency of the PVA providing a better rate of control over suction. You simply apply the PVA, wait for it to dry and apply the second coat. If you’re starting out (which I assume you are), then I’d always recommend that you use 2 coats of PVA- it makes skimming so much easier.
To get a complete breakdown on PVA before plastering then check out this article!
There is another product you can use. PVA is good but there is a better product. Its called blue grit. This stuff sticks to anything and leaves a gritty coat over the area your working on.
This is the product description:
“Febond Blue Grit is a high performance, plasterers grip coat bonding agent specifically designed to provide an improved key to smooth surfaces. Containing a fine aggregate, it provides a mechanical key to backgrounds such as plaster, concrete, painted surfaces, textured surfaces and ceramic tiles. One coat application, coloured blue to indicate coverage.”
I use it quite a lot, especially on existing walls. If your walls are in really bad shape or you’re struggling to get the walls prepped I’d use this stuff over PVA. It leaves a lovely key to plaster onto which increasing the bond to the walls.
There is a problem though – It’s quite expensive. If you look online I think you can get it cheaper but it’s still quite dear. That’s why everyone uses PVA. It’s still a good product but Blue Grit is definitely far more superior.
When your wall is PVA’d or Blue gritted you’re ready to get plastering. That is the complete list for preparing walls for plastering
But before you go, I’ve got a question for you:
Are you ready?
I’m sure your reading this with the intention to start plastering.
If your learning how to plaster then you might be reading this to get some information to finally start plastering for yourself. Let me give you some advice: If your looking for some help then the fastest way to learn is by seeing.
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