Sealing Plaster – How to Easily Seal Plaster in 4 Steps

August 31, 2020

To get the best results with your plaster, sealing plaster is an essential step and key to the finishing process. Sealing plaster makes new plaster less absorbent, allowing your paint to adhere properly to your plaster.

Plastering your walls is a great investment. Whether it’s being applied to plasterboard, repairing traditional lathe, or adding a fresh coat over old, this fixer-upper is well worth the mess and effort. A coat of plaster makes your walls smooth, durable and ready for living. Plaster also lasts for many years with the right care. 

Not sealing your plaster can lead to poor results. It may bubble during drying, so your walls end up looking rough and unfinished. Without a sealant, your paint may never fully bond with the plaster, leading to issues with peeling that are unsightly. This can also cause problems to develop with the plaster itself, affecting how long it will last.

Working with a professional is a great way to ensure that your plaster sealing project goes smoothly. Click to easily find a plasterer in your area.


Essential Materials for Sealing Plaster

For a great job, it’s important to use the right kinds of materials. This includes the things you need to protect your workspace such as drop cloths, as well as things to protect your own health. When a professional tackles a plastering project they’ll bring gear like safety glasses, coveralls and a mask to keep themselves safe from the plaster dust as they work. 

You’ll also need to have these supplies for sealing: 

  • Paint roller and paintbrush to spread your product around to seal it
  • Extension pole to access hard to reach areas (and make the job easier on your back and arms!) 
  • Ladder to make it easier to reach the entire plastered wall 
  • Water-based emulsion for the sealing process 
  • Paint tray to load up your emulsion mix more easily

Paint Roller | Paint Tray | Ladder

Image Credit | Image Credit | Image Credit

Choose brands that you like to work with. It may also be a good idea to choose disposable items to make your cleanup simple.

Although it will take some time to have your plaster sealed, it improves the overall appearance of your walls and prepares them for paint. This way, you can apply the paint colour of your choice to realize your decorating vision in your room. But before you pick up the paintbrush, make sure you follow these steps to seal your plaster properly.

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4 Steps to Sealing Plaster

4 Steps to Sealing Plaster

1. Get The Area Ready

Your first step is to get the area prepped for the upcoming task! Sealing can be a messy job. It’s important that it is free from any furniture that might get in the way. If you’re sealing your plaster after a recent plastering project, you may be in a good position to get started already and have the space cleared from the plasterwork. 

2. Ensure You Have The Essential Materials

Before you start, make sure you have all of the materials you need on hand. This will get you off to the best start, and reduces the chance you’ll need to put the work on hold to get something that’s missing!

3. Apply a First Mist Coat

A mist coat is a common way to seal the plaster. The water in the emulsion is absorbed by the plaster, making it become less absorbent. This allows the paint to dry on top, forming a coat that provides a seal against the plaster underneath.  

Allow this coat to dry thoroughly so it can cure before you start with painting for the best results. If you apply paint while it is still damp, your paint can peel and leave an unsightly mess that needs to be fixed before you can move on. 

This is a messy step — the added water makes it drip much more easily and can easily make a mess of your skirting boards if the drips are left to dry. Wipe off drips or roll them out right away so they can’t dry and mar the surface of your newly plastered walls. 

4. Apply Several Coats as Needed

Although it may seem tempting to apply thick coats as it seems to offer better coverage, this isn’t the best way forward. It is actually better to apply several thin coats, allowing each to dry in-between applications. Two to three coats are recommended, but you may require more depending on the type of coverage you need. 

Keep in mind that if you are going with a white topcoat, it’s best to use a white emulsion for your mist coat so your coats will build up to a nice, even white colour. Otherwise, you may find yourself applying several more coats than you’d expect!

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The Benefits of Sealing Plaster

The Benefits of Sealing Plaster

Now that you know sealing your plaster is an essential part of the process, you can plan to carry out these steps to guarantee the best results. Beyond the knowledge you are doing this correctly, you’ll also be satisfied with the benefits of a good seal beyond the look of the plaster itself.

Properly Sealed Plaster is Cost-Effective

One of the top benefits of sealing plaster properly is that it will help save you money! Sealing the plaster makes it less absorbent so your paint will go further. If you plan to use a higher-end brand of paint, you’ll want the application to be as efficient as possible. Making less paint do more is a great way to pay attention to your budget. Plus, it also makes your paint look better since the undercoat is a smooth, even colour. This is especially important if you are using a deep or rich colour that may need a few extra coats to be truly finished.

Bidvine Tip – Check out this article to learn more about painting new plaster

Sealing Plastering Reduces Drying Time For Painting Later On

Sealing plaster can also save you time. Although the sealing process does add an extra step, you’ll see better results with your paint. It won’t take as long to dry between coats, allowing you to tackle the painting in a shorter time frame. Generally, it also takes fewer coats until paint can be declared complete. This means you’ll be able to start moving your furniture back in and hanging your wall decorations that much sooner to enjoy your space! 

However necessary, sealing plaster is still a messy job. It can feel like a big obstacle standing in the way of you enjoying your room. Plus, you may not feel prepared. After all, it requires some level of expertise to apply the coats evenly. For the best success, you may want to hire a professional to apply your plaster and look after the sealant. 

Ready to begin your plastering project? Learn more about the factors that influence the cost of plastering in our handy Plastering Price Guide.

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Plastering is the process of covering uneven or rough surfaces with plaster and is commonly done on walls and ceilings, usually for two purposes. Firstly to provide structural support to the wall or ceiling and then secondly, for decorative purposes to cover up imperfections and provide a smooth surface for renovation.

Can You Plaster Over Paint?

The answer to that question is, to put it simply, yes. Yes, you can plaster over paint, however, there are factors which should be considered first.

Your first step is to assess your wall. If the paint on your wall is in good condition, then a professional will likely be able to start the plastering process straight away. Paint that is in ‘good condition’ won’t have damages or cracks and won’t be peeling either. It is also best if the walls themselves are clean of dirt, and dust.

If however, the paint is not in good condition or the wall has recently been painted it is best to avoid plastering over the paint directly. This is because walls which have paint that is no longer in good condition will either need repairs or a professional may need to strip the paint first. more
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Plastering Trowel

How to Plaster a Ceiling Step by Step

So you’re ready to take on plastering your ceiling, are you? Well, just follow the simple steps outlined below and you’ll soon be well on your way!

1. Gather Your Tools and Equipment

Before you begin plastering your ceiling, you will need to gather a few tools first. Keep these handy for the duration of the project. Then, if you need something mid-project it will be close at hand.

We’ve included a list below of the most important tools and supplies for plastering a ceiling:

  • Plaster
  • Plastering trowel
  • Ladder
  • Mixing stick
  • Sandpaper
  • Clean water and sponge

Once you’ve gathered all the essential supplies then it’s time to begin the prep work.

2. Prepare the Area

Plastering a ceiling is messy there is simply no better way to put it. You’re balancing on a ladder with wet plaster on a trowel that you spread across the ceiling. This means, there’s a pretty good chance that some of it is going to drip down and land on your or the surrounding area.

The best way to counteract this is to plan ahead. Remove as much furniture as possible from the room. Then, cover any remaining furniture as well as the floor with a sheet of plastic. Take special care to ensure that the entire floor is covered. You don’t want plaster falling and hardening on your carpeting or hardwood.

To protect yourself, you should wear a renovation mask and some old clothes. While the mask prevents plaster from landing in your mouth, the clothes will protect your skin. Not to mention that using old clothes means you won’t destroy any favourite pieces.

Plaster Ceiling

3. Prepare the Ceiling

Do you have uneven patches on your ceiling? Then you should sand these down first. You don’t want the faults of your old ceiling to carry over after you are finished your project.

Then you’ll need to tidy up. Even if your ceiling is newer you should still follow these steps and tidy to remove any hidden dust. The good news is, that cleaning your ceiling is relatively easy. Use a vacuum to remove old cobwebs from the ceiling and then a sponge with some soapy water to wipe up any dust that remains. After this, get rid of any traces of soap residue by sponging the ceiling with clean water after following this step.

Are you plastering on a surface that has been exposed to oil? Then use a degreaser. If you don’t remove the oil before you plaster, it won’t set.

If you have a hole in your ceiling, you will also need to take some steps to patch this up first. more
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What Is a Mist Coat?

Essentially, a mist coat is a diluted coat of emulsion. It's especially useful if you are painting new plaster that has not been treated before. This is because standard emulsion is too thick to paint fresh plaster effectively. You will need to use a paint that is watered down. The water will sink into the surface, allowing the paint to bond to it.

Standard emulsion painted onto an untreated wall will not dry well. It is likely to crack and to peel. If you don't use a mist coat, you will find that any normal emulsion you apply afterwards sits on the surface. Painting your surface only with a standard emulsion and avoiding a mist coat will mean that you have to repaint it sooner. more

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