How To Repair a Cracked Plaster Wall

Image credit: Andrea de Poda

Cracks in plaster aren't always sinister and a sign that something is seriously wrong with your home. Plaster cracks and splits over time as buildings expand and contract, and even the best maintained homes will have cracked plaster from time to time. A few hairline cracks in plaster doesn't mean that the whole wall has to be replastered, as filling and repairing the cracks is a simple task which even people with minimal DIY skills can undertake themselves.

Plaster or Plasterboard?

The way we construct our homes in the UK has changed over the years. If you are in an older property, built before World War II, then your home is likely to have brick walls with layers of plaster over the top. In more recent years, construction has changed and stud partition walls are put up and then plasterboard placed over the top. There really is no difference in the way in which the different sorts of plaster walls are repaired, so although it is a good idea to have a basic idea how your home is built, it doesn't make much difference in practice.

Tools Required

Filler can be found in pretty much any DIY store and shouldn't
cost too much to buy.

Plastering a whole room is most definitely a job for the professionals, as it is difficult to get a smooth, even finish. Plastering is often described as an art rather than a skill, but repairing small areas of damaged plaster or cracks requires far less skill. 

In terms of tools, you will need some sandpaper, a chisel, a knife and some filler. All of these tools are widely available from DIY stores. There are many different types of filler on the market. Some are ready mixed, some have to be mixed with water, and some have special properties such as being antifungal or water resistant, so it may be best to get professional advice from the assistants in store about what product is best for your individual needs. Buying everything that you need to complete the job shouldn’t cost any more than £25.

Getting Started

If the cracks on your wall are relatively small, the first part of the process is to widen out the crack to make it large enough to be able to get the filler inside. This is where your chisel comes in handy. As well as widening the crack a little, make sure you remove any other bits of plaster which appear to be starting to flake off and use a wire brush to clean the area where you are going to be working of any loose flakes.

If you have bought filler which needs to be mixed, mix it up carefully following the instructions on the packet. Don't mix up more than you think you will need as it is useless once it has dried out. Whatever type of filler you are using, stir it with a stick to make sure it has no lumps in before you start using it.

Applying the Filler

Small initial cracks can ultimately develop into large chunks flaking away. Image credit.

Some experts advise damping down the edges of the crack which is being repaired with a cloth, as this will help the filler stick not only to the inside of the crack but to the edges too. This should stop the filler just falling out again once it dries. Always apply the filler at right angles to the crack, making sure it is pressed in firmly to fill the whole crack. Keep repeating the process until you have filled all of the cracked areas around the room. 

Don't worry if the surface doesn't look particularly smooth at this point as that can easily be rectified once the filler has dried. Fillers differ in the time they take to dry out, but always stick to whatever recommendations there are on the pack. Overnight is usually plenty of time to allow the filler to dry out completely.

Finishing

Once your filler has dried out completely, you can then sand it and redecorate the patch of wall. Fine sandpaper is usually best for this job as you want a smooth, even finish, and it may be easier to work with the sandpaper around a block of wood to help you grip it. Work over the areas which have been filled, taking your time to make sure you get as professional looking finish on the wall. Wipe over the sanded area with a damp cloth or piece of kitchen paper and leave it to dry out. 

Then all that remains is to paint or wallpaper over the filled areas, leaving your wall looking as good as new.