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.

Plasterer Price Guide

Thousands of people ask Bidvine for help with their projects every year. We track the estimates they get from local professionals, then we share those prices with you.
Price Range

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!

Plasterers near you
Thousands of people across the U.K. ask Bidvine for help with their projects every year. Tell us what you need so we can bring you the right local professionals for your project.

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.

Featured Image Credit 

Related Articles
The Essential Step by Step Guide to Lath and Plaster Repair

Before you embark on a big DIY project, it’s important to do your research. This is especially true when it comes to home repairs for lath and plaster. Making a mistake could be costly, so it’s best to understand what you need to do even before you start! 

If you are tackling a project with your walls, you may need to learn about lath and plaster. This is a popular way to cover walls in homes both new and old. You’ll first need to develop your technique to do it properly. Read on to find out exactly what you need to know to get started. 

Planning on hiring a plasterer for your project? Easily compare plastering costs when you submit a free request.

Lath and plaster

Image Credit

What is Lath and Plaster?

Lath and plaster is a process used to finish interior walls and ceiling. Lath is the name for the narrow boards of varying widths that are fixed to the timbers inside your walls. This creates a horizontal working surface that allows the plaster to bind to it to give your walls a lasting surface.
Plaster is a mixture of gypsum cements that, when mixed with water, creates a putty-like substance that can be smoothed onto your walls. When it dries, it creates a hard, solid surface. It usually requires several coats to build up the walls to the proper thickness. more
How to Smooth Walls Without Plastering

Being able to smooth your walls without re-plastering is easier for everyone. To give you some ideas, we’ve gathered together a list of 9 fast, cost-effective alternatives so that you can smooth walls without plastering!

If your walls do need plaster, a plastering project could be easier than you might think! Simply submit a free request on Bidvine with details of your project, compare bids from top local professionals, and hire the best!

1. Fill Holes

Before cleaning up scuffs or sanding your walls, you’ll want to make sure you’ve filled any holes in your wall. Often when hiring someone to smooth your walls, they will do this first, along with other processes which will be covered in further detail below.

Holes can be filled with ‘filler’ and later smoothened via a process called sanding. Filling your walls before sanding ensures an overall smooth finish, with no gaps in-between. Filling your walls will provide a base for a fresh layer of paint.

2. Smooth Walls by Sanding 


Image Credit

If you are looking to smooth your walls without plastering, one of the best choices is sanding. Hiring a contractor to smooth your walls will more than likely include this. Hiring a professional to sand your walls is your best bet. They will most likely use an electric sander – a quick and smooth alternative for large scale projects. more
How to Plaster a Wall (Complete Guide with Top Advice!)

Learning how to plaster is an advanced D.I.Y. project. The techniques and methods involved in plastering are not easy to master. Hiring a professional plasterer is the best way to ensure your plastering project is a success.

If you’re new to plastering, this guide will take you through everything you need to know. Whether you want to know how to plaster damaged walls, how to mix plaster to the right consistency, or how to plaster external walls, we will explain every step of the process. So read on to discover how you can become a plastering pro!

Tools and Equipment You Will Need

  • Plaster
  • Sponge
  • Bucket
  • Trowel – to apply the plaster to the surface
  • Hawk – to hold the plaster as you apply it to the surface
  • Wire scratching brush
  • Sandpaper
  • Mixing stick
  • Ladder
  • Jointing knife – allows you to plaster in tight corners and to create straight lines at the edges
  • Clean tap water

Preparation Before Plastering

Plastering is usually a very messy process. Make sure that you use protective plastic and drop cloths to cover large furniture and your flooring. You will also need to cover any electrical sockets and fittings. Cut the power to the room.

Cracked Wall

Image Credit

It’s very important to make sure that your tools and surface are clean before you begin mixing the plaster. Any dirt or grit that is left behind could leave you with an uneven finish. Wash the surface gently with warm water but don’t soak it.

Do You Have a High Suction or Low Suction Wall?

Properly preparing the surface that you want to plaster is essential if you want to achieve a great finish. Many D.I.Y. plasterers are unaware that the suction of their wall has an enormous impact on the finish of their work. But why is suction so important? Suction is vital because it bonds your plaster to the wall. So, before you start plastering, you’ll need to determine if your wall has a high or low level of suction.

A high suction wall will soak up moisture very quickly. This will cause your plaster to dry too rapidly, and you won’t be able to smooth it out. However, if your wall is low suction, you’ll find that your plaster struggles to bond to the surface. The plaster will be fragile and it may start to crumble.

The best way to check the suction of your wall is to do a patch test. Take a small section of your wall, around 50mm x 50mm, and apply freshly mixed plaster to it. Leave the area for a few minutes. Use your finger to lightly trace a line through the plaster. more

Why Bidvine is the best place to hire experts

Answer a few questions and we match you to the right pros.

Get custom bids from pros who match your needs.

Compare bids, send messages and hire the right pro for you.