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Plaster has been used in one form or another for several thousand years to decorate different types of buildings throughout history, from humble houses to grand mansions.
And while the mixtures and ingredients have changed over the years, the processes, skills, and finished results are much the same as they've always been. Today, companies like Top Notch Walls are still providing high-quality plastering services at a professional level, and these skills are in high demand.
However, it's a fact of life that plaster walls can become damaged, either through negligence, age, wear and tear, accidents, or 'home improvements'. Because of this, repair work is often necessary, and when this becomes apparent, you need to know what to do next.
So, here's the Top Notch Walls guide to repairing plaster walls to set you on the right path.
In certain circumstances, it's entirely possible for someone to repair their own plaster, although it's important to follow the right procedures according to the type of damage and the original plaster used.
First, you need to establish what type of substrate (the wall surface beneath the plaster) is involved, as this will determine how easy or difficult the task will be!
Let's see what the possibilities are:
Although this has largely been replaced by plasterboard (also called drywall or dry lining), the plaster and lath technique was extensively used between the 1700s to the mid-1900s in most homes. In this method, thin timber strips were nailed horizontally over vertical joists to form a framework on internal or non-load-bearing walls. A gap of around 6mm was left between each lath to help the plaster stick to the surface.
Three separate layers of plaster were usually applied: a render layer, a floating layer, and, finally, a setting layer that could be decorated.
The chances are, if your home was built pre-1940, you will have plaster and lath walls (or ceilings) somewhere in your home. If so, then there's a fair chance that it has seen better days, and some areas will have suffered damage.
In this case, you'll need to fix it or call in a professional to do the job.
This is a quicker and more cost-effective way of covering walls, which is why it is the usual method of making 'stud walls' these days.
The plasterboard - made from gypsum sandwiched between tough paper - is nailed onto a wooden frame, and skim plaster is applied over the surface, usually with jointing tape between each board.
Technically, this doesn't really count as a plaster wall, although you still might need to repair minor cracks or holes, so it's only right to include it in our guide.
Wet plaster is commonly applied to brick, CMUs (concrete masonry units, also called breeze blocks or cinder blocks), and stone walls, usually with a scratch coat of cement render or gypsum beneath.
These surfaces are notorious for their porous qualities, known as the suction level. Certain surfaces have a high suction level, drawing moisture directly from the plaster and into the substrate, which causes the plaster to dry too quickly, resulting in cracks or blown plaster.
A competent professional will be aware of all of these methods, and if they're of the same standard as Top Notch Walls employees, they'll know many others, including Venetian plastering and the safe removal of Artex. They will also know the best ways of repairing different types of plaster, and we'll dive into these now.
Depending on the size of the job, you'll need the following equipment:
Cracks of all sizes can ruin the appearance of your plaster, typically caused by thermal movement, exposure to moisture, or settling foundations.
Before you start any repair work, it's important that you check the size of the cracks. If they're 5mm or less, then you can go ahead and fill them. Anything between 5mm and 15mm may be more serious, particularly on brick or stone walls. You might want to consider getting a professional to examine the walls in case the masonry beneath is damaged.
And if the cracks are larger than 25mm, then it's definitely time to call someone to take a look!
Cracked plaster on the plasterboard is fairly common, as the panels are flexible to a degree and tend to move with the structure. These are usually pretty easy to cover without too much hassle.
As for plaster and lath, it's possible that the wooden strips have rotted over the years, so it's essential to make sure that they are sound before you repair the plaster. However, if this is the case, the plaster is more likely to sag than crack.
Assuming that the cracks are narrow (less than 15mm) and there are no other signs of damage, then you can start work. For more information, check out our post “How To Fix Cracks In Plaster Walls".
Cover the immediate area and any furniture with dust sheets. This might seem excessive, but it's better to be safe! Also, make sure you wear safety goggles and a dust mask.
Use the thin blade to carefully score along the cracks to make them wider. Remove any loose plaster and use the vacuum cleaner to get rid of dust.
If it's only a small area, mix the filler in the plastic pot according to the manufacturer's instructions. Dampen the area thoroughly - a plant sprayer or damp sponge will do the trick, but don't overdo it; it should not be soaking wet.
Apply the filler using the filler knife, making sure to press it in firmly so it reaches the base of the groove. It's okay to make it slightly thicker over the crack, but always remove excess filler from either side using a blade (carefully!) or a damp sponge.
Allow the filler to dry fully before sanding it lightly to get a smooth and level surface. Use a medium-grade sandpaper first, followed by a finer one.
This includes things like screw and drill holes left over from pictures or fixtures that have been removed. You might also have dents and scrapes from when the wallpaper was stripped.
On plasterboard walls, you'll probably find that the holes have ragged edges and loose material protruding outwards. Use a tool handle to push this inward and sand lightly over the top.
Mix the filler and scrape this over the holes in several thin layers rather than all in one go (there's less chance of the plaster 'bubbling').
Top tip: run a squeegee over the wet filler to remove any excess, as this provides a super smooth surface.
When dry, sand the area lightly and decorate as desired.
It's one thing to fix cracks, but quite another to repair large holes. Only tackle this job if you are absolutely confident!
This type of damage on internal walls is often a result of relocating light switches or sockets, so always make sure that the wiring is 100% safe before starting work.
Filler won't usually do the trick here, so you'll need a proper plaster.
Now, there are several methods that can be used to repair holes, but it depends on the cause, the size, and whether it's in drywall or not.
For a hole in the plasterboard caused, say, by the relocation of pipework, you can use an off-cut from a spare piece of plasterboard that's been trimmed down to size. This can then be pressed into position with mesh tape placed over the top to keep it in place.
For large areas, perhaps where a door frame has been adjusted, you'll need to apply a fresh layer of plaster.
For this type of plaster repair, use a hammer and chisel to remove any loose pieces and get rid of dust with the vacuum cleaner.
Next, brush some PVA glue (or bonding agent) into the repair area to help the plaster bond.
Mix the plaster according to the manufacturer's instructions, and apply the first coat. This should be a thin layer - applying plaster too thickly is a big mistake! It will sag and take much longer to dry.
Before it has dried, scratch the first coat with the end of a trowel to make a criss-cross pattern.
Mix the next batch of plaster and add the second coat using a plasterer's float. Wait ten minutes, then run the float over the area again, making sure you wet it first.
Sand when completely dry and paint or wallpaper as you wish.
This is almost inevitable in 'high-traffic' areas or when kids are around!
But don't worry, these can usually be fixed fairly easily.
First, get rid of loose debris with a small brush or vacuum cleaner. Next, mix your chosen filler to a thick consistency and mould it into shape over the damaged area.
Put masking tape over the top on both sides of the corner, ensuring that it sticks to either side of the existing plaster. Press this lightly with a straight edge (like a ruler) to get a flat surface and leave it to dry before removing the tape.
This will protect the filler and create a perfect corner edge.
Once completely dry, it can be sanded and painted. Our post "How To Paint New Plaster" maybe interest you. You can check it out.
Always choose a known and trusted brand, like Ronseal, TouPret, Gyproc, or Polycell. It's difficult to say which is the best patch plaster, as there are so many excellent ones.
Also, it depends on the existing wall and original plaster, as older houses may need a specialist mix that's compatible with these.
This is the most important aspect of any home improvement or DIY work. If you can patch holes or fill cracks yourself, that's great. But when the damage is too great, or there's a serious underlying issue, you need a helping hand.
And when you do, feel free to call Top Notch Walls for more advice!
While you're here, take a look at our post "How To Fix Plaster Ceiling Cracks" for more additional information.
