Having your walls plastered is one of those lovely jobs that finishes off all the hard work that has gone on beforehand.
Of course, it is also a really messy job so it pays to either clear the area to be plastered of all furnishings, or at the very least cover it all up properly.
You will also need to think about where the plasterer is going to get water from and ensure their route from a water source to the room they are working in is protected.
Plastering New Walls
In the case of new builds, plaster can be applied directly to plasterboard. In preparation, plasterboard screw heads should be countersunk and the joint between boards taped. Metal angle beads are used to ensure a crisp finish around external corners.
Then it is simply a case of applying a layer of plaster. It is usual for ceilings to be set with plaster before work commences on the walls. All blockwork walls to be plastered should receive one coat of sand and cement render, known as a scratch coat.
This is left to set and then scratched, using a float with nails in it, in a swirling fashion to provide a stable key for the next coat, which is applied when the first scratch coat is still green but before it has dried out completely.
These two coats can be used to ‘dub’ out and fill any indentations or undulations in the wall.
At a point where the plasterer judges that the render has set sufficiently, the topcoat plaster skim finish is applied. This should be smooth and not show any trowel marks or undulations as it is, essentially, the finished surface of the walls and ceilings in your new home.
Alternatives to Plaster
Many new homes these days are not actually plastered at all. It is usually internal walls or stud walls but sometimes the inner faces of exterior walls too are simply lined with plasterboard before being painted or papered over — no plaster skim coat.
Of course the main reason for this is cost, so there’s no need for a plasterer. Instead, the screw holes are simply filled, the joints between the boards covered with paper tape (scrim) and then jointing compound, and you’re good to go. It is known as tape and jointing.
While this method is cheaper than plastering, care needs to be taken — if plasterboard gets too wet it becomes weak, and it is easy to damage the paper surface of the plasterboard if you’re not careful. Plasterboard is also very absorbent so it should be sealed with a dilute PVA solution or a product such as Gyproc Drywall Sealer first before painting.
Plastering Walls in a Renovation
Ensuring your walls are plaster-ready will save you money when it comes to paying your plasterer. Whilst most plasterers are quite happy to remove old plaster or to fix new plasterboard, this will all add to the time they spend on the job and increase their final bill.
Preparing the Room
Before your plasterer starts, it helps if you can clear the room out and cover anything that can’t be taken out of the room — plastering is a messy job.
Your plasterer will need access to a water supply. Aim to provide a route to the water source that doesn’t involve traipsing plaster and mess through your entire house — and cover carpets too.
Remove old skirting boards before plastering — most plasterers will find it easier to plaster down to an inch or two above the floor than to skim down to the top of skirting.
However, if you want to keep your skirting boards in place then most plasterers should be able to skim down to the existing skirting boards, although this is more time consuming.
Plasterboard How Tos
Plastering Over Old Plasterwork
If you want your plasterer to apply a fresh skim coat to old plaster walls, you will need to prepare your walls. Any damaged and crumbling old plaster will need to come off the walls, before the brickwork beneath is cleaned off.
Preparing your walls thoroughly before your plasterer starts work will save time and money. Image: British Gypsum
Scrape away any old pieces of wallpaper and apply an adhesive, such as a diluted solution of PVA. Alternatively, use a product such as Blue Grit, an adhesive containing small sand-like granules that sicks to the wall and provides a really good key for a new plaster coat.
Thistle Bond-it is another good product. Both are simple to paint directly on to walls. Once dry your plasterer can apply a skim coat directly.
Plastering Directly to Brickwork
Although uncommon these days, it is sometimes still necessary to plaster directly to old brickwork or blocks. This is more commonly done on small areas of wall where sections of old plaster have come away and is done as a ‘patching in’ job, rather than over an entire wall.
Before old brickwork can be plastered it will need to be cleaned off and prepared.
Plasterboard is now more commonly used. Image: British Gypsum
It is vital that the condition of these walls is assessed and rectified where necessary — crumbling old brickwork will not take a new coat of plaster.
The surface of the old brickwork will need to be brushed down using wire brushes before a layer of bonding, or browning, a render like substance, is applied to bring it up to the same thickness as the old plasterwork, before a plasterer skims the entire surface.
Can I Plaster Over Painted Walls?
If you have old painted walls that you would like to have skimmed, you should first sand and clean them off. Coating them with a weak PVA solution, Blue Grit or similar will help the new skim coat to adhere nicely to the walls.
Before the invention of plasterboard, plastering was a more laborious and expensive task. Plastering directly to bare brickwork or blocks, known as ‘wet plastering,’ is still favoured by some for its superior soundproofing.
A cement render or gypsum backing (known as a scratch coat) is first troweled directly onto blockwork before this is finished off with a thinner skim coat.
The downsides of wet plastering are that it takes much longer to dry than a skim coat on plasterboard, plus it can be prone to cracking.
Plasterboard is far simpler to plaster over than bare brickwork and as it only needs a skim coat — it is generally the cheapest option too. In addition, fixing plasterboard to bare walls by screwing it to timber battens means a layer of insulation can be added in too if required. In other instances, plasterboard can be ‘dabbed’ to the bare wall. This is where sheets of plasterboard are stuck to the wall using ‘dabs’ of adhesive.
How to Fix Plasterboard
By cutting sheets of plasterboard to fit yourself, you will save your plasterer time when it comes to do the job — and therefore save you money. A handsaw or jigsaw does the job.
You could even fix the plasterboard to the wall yourself. The easiest way to do this is to screw it directly to timber battens you have fixed to the wall and ceilings — use plasterboard screws and ensure the screw heads are sunk below the surface of the boards.
The joints between the boards will need to be covered with scrim, a mesh tape, before the plasterer skims.
Although plasterers’ rates will vary depending on where in the country you are and who you speak to, you can expect to pay from around £135 per day.
Ensure you find out how many days your plaster will be on the job or alternatively, agree on a fixed price for the job.
Anything from £450-£800 to plaster a medium sized room, including the removal of old plaster, the fixing of plasterboard and skimming is to be expected.