Should you discover that there are cracks or patches of loose plaster on the internal walls of your home (usually found when you redecorate), then they will need to be repaired.

Small cracks can be repaired using an appropriate flexible filler, then sanded to a smooth finish.

Larger patches of damaged or loose plaster (as pictured below) will require re-plastering to obtain a suitable surface for decorating or painting over.

Damaged plaster

Achieving a good finish when plastering a large area, such as a complete wall or ceiling relies on the plasterer having a good technique and a great deal of practice, fortunately patch plastering can be carried out by a competent DIYer. There are various plasters available for the job (see differant types of plaster). You could use Browning or Bonding plaster with a topcoat of Multi-finish for the repair, or as I prefer to use, one coat plaster which is available from the larger DIY stores in various sized bags from around 2.5 kg to 12.5 kg, so you don’t have to purchase a 25 kg bag of plaster, of which 3/4 will end up at the local tip as its ‘shelf life’ is not very long. One coat plaster also has the advantage of drying to a White finish.

Safety tip :-  Mix the plaster, preferably outdoors wearing a face mask to avoid breathing in the dust.

To carry out the repair, start by placing a dust sheet or old towel to protect the floor, remove any bits of loose plaster and brush away any dust using a soft hand brush or old paintbrush. The wall you are going to plaster over will be dry so splash or flick a little water on it to wet it down, you don’t have to drown it !, this is done to stop the brickwork from absorbing the water from your new plaster too quickly. Wait a couple of minutes for the water to soak into the wall. The plaster can now be applied to the wall, if the patch has a depth of around 12mm (1/2″), you should be able to plaster it in one go, if it is deeper,  you may have to make two applications, otherwise the weight of the wet plaster will drag itself away from the wall. If you have to apply the plaster in two applications, when the first has dried out and has become firm to the touch, scratch the surface with, as an example a large kitchen fork (a plasterer would use a scarifier to do this), this helps the second application of plaster ‘key’ to the first.

Apply the plaster using your plastering trowel, until it is level with the surrounding plaster, remove any excess plaster around the patch with the edge of the trowel. Allow the plaster to dry out a little (until it is reasonably firm to the touch), flick a little water onto the new plaster and clean your trowel with water leaving it wet, smooth over the new plaster with the trowel whist continuing to flick water on it , doing this will produce a much smoother plaster finish, this is sometimes referred to by plasterers as ‘bringing the cream to the top’, a phrase which will become self explanatory when you do this.

Let the plaster dry out thoroughly and any excess plaster can be smoothed flat using a sanding block (a short piece of 3″ x 2″ 75mm x 50mm timber with sandpaper around it will do).

Before you paint over the new plaster apply an undercoat, or if you are wallpapering apply one or two coats of wallpaper adhesive to prime and seal it.

Used as a base coat on walls, brickwork, block work, breeze block, plasterboard. A 25 kg bag will cover approximately 3 – 3.5 square metres at a depth of around 12mm. Setting time is approximately 2 hours.

• BONDING.

Used as a base coat on walls, brickwork, block work, breeze block. This plaster has excellent adhesive qualities and will therefore bond to most surfaces. A 25 kg bag will cover approximately 2.5 square metres at a depth of around 12mm. Setting time is approximately 2 hours.

• MULTI FINISH.

Used as a top coat to give a smooth finish on Browning and Bonding base coat plaster. A 25 kg bag will cover approximately 10 square metres at a depth of around 2mm. Setting time is approximately 1 – 1.5 hours.

• BOARD FINISH.

Used as a top coat on plasterboard. A 25 kg bag will cover approximately 10 square metres at a depth of around 2mm. Setting time is approximately 1 – 1.5 hours.

• ONE COAT PLASTER.

Ideal for small DIY projects, as the name suggests only one coat is required and it is suitable for most interior surfaces. It can be purchased in various sized bags from 2.5 kg to approximately 12.5 kg. Setting time is approximately 2 – 2.5 hours and when fully dried out gives a white smooth finish.

Many recently built properties have plasterboard stuck in place on interior walls (Dot & Dab), this method of fixing the plasterboard’s to the walls leaves voids between the plasterboard and wall, therefore a good knock with a piece of furniture etc, will result in a hole in the plasterboard (see fig 1). The same problem occurs with none load bearing walls such as dividing walls between bedrooms, they will more than likely be constructed from timber and plasterboard/drywall.

Fortunately these holes can be repaired fairly easily by anyone with a little DIY skill and a few tools.

Start the repair by cutting the hole in the plasterboard as square as possible (see fig 2) using a pad saw or sharp knife, taking great care the knife does not slip as a lot of pressure may need to be applied to cut through the plasterboard.

If the hole when squared up measures as an example 5″ (125mm) square, cut a piece of plasterboard 4 3/4″ (120mm) wide by 7″ (175mm) long. Note you may have to reduce the longer measurement if there isn’t enough space to to slide the new piece of plasterboard behind the existing plasterboard.

Screw a couple of drywall screws around 1″ (25mm) apart in the center of your cut piece, apply a grab adhesive (Gripfill, etc) to each end of the cut piece (see fig 3) and slide the cut piece of plasterboard into position inside the hole, now pull on the two drywall screws gently so the adhesive bonds to the inside edges of the existing plasterboard, hold the piece in position for a couple of minutes until it bonds and then allow the adhesive to set (see fig 4).

As an alternative to using drywall screws for grip you can poke a small hole in the centre of the piece of plasterboard with a screwdriver, then pass a piece of string through the hole and tie it to a small piece of wood (e.g. a peg), when you have placed the piece of plasterboard in position and the adhesive has set , simply cut the string flush with the hole it comes through.

When the piece of cut plasterboard is stuck in position, the remainder of the  hole can be filled with an appropriate plaster (e.g. one coat plaster), or if it is only a small hole use a flexible filler. If your finished plaster or filler is not very smooth, use a sanding block to obtain a good level and smooth finish (a short piece of 3″ x 2″  75mm x 50mm timber with sandpaper wrapped around it will do the job).