Wall & Ceiling Repairs - Build Your Skills Leaflet 208

In a typical house, masonry walls have a hard plastered finish and the ceilings are surfaced with sheets of plasterboard. So are any internal timber-framed partition walls.
In older properties, the wall plaster may be much softer, and ceilings will be finished with lath and plaster. This is a system involving nailing slim wooden laths to the undersides of the joists and then pressing wet plaster up against them. The plaster is squeezed through the gaps between the laths to form a key that holds it in place.

Lath and plaster may also be used on the walls of older properties. On external walls the laths will be nailed to wall battens, leaving a cavity between the plaster and the masonry. On internal walls the laths will be nailed to the timber frame.
All these surfaces may crack due to movement of the structure, and can be damaged by accidental impacts. This leaflet tells you how to carry out the necessary repairs.

Mix the paste thoroughly with a small filling knife, adding more powder or water as necessary.

Draw the knife along the line of the crack to remove any excess filler.

Let the first layer harden, then apply more filler to complete the job.

Using Fillers

Mixing Powder Fillers

The most economical material to use for carrying out small-scale repairs to walls and ceilings is Wickes Interior Filler - a fine powder which you mix into a paste by adding water. It bonds well to plaster and plasterboard surfaces, and dries quickly to a hard finish that can then be sanded smooth.
The easiest way to mix small quantities of filler is to put some powder in a bowl and trickle in a little water. Mix the paste thoroughly with a small filling knife, adding more powder or water as necessary to achieve a firm but mouldable consistency. [PIC 1]
The filler starts to set as soon as it is mixed, so don't mix up more than you can use within about 30 minutes.

Filling Cracks

Use the corner of your filling knife to rake out the crack and undercut the sides at an angle to give the filler a better key. Then use an old paintbrush to brush out any dust and loose debris.
Wet the crack with water, applied with the same old brush. Then take some filler onto your knife blade and fill the crack by first drawing the knife across it to press the filler into place. Then draw the knife along the line of the crack to remove any excess filler. [PIC 2]
Leave the filler to harden for about an hour. Then use fine glasspaper wrapped round a sanding block to smooth the filler flush with the plaster.

Filling Holes

Treat shallow holes in solid plaster in the same way as for cracks, removing any loose material and brushing out dust before wetting the surface to prevent the filler drying too quickly and cracking.
Press some filler into the hole with your filling knife. Fill holes up to about 6mm deep with one application, using the knife blade to remove excess filler, and finish the repair flush with the surrounding plaster.
Fill deeper holes in two stages to avoid any risk of a thick layer of filler slumping. Let the first layer harden, then apply more filler to complete the job. [PIC 3]

Wall & Ceiling Repair Techniques

Patching Plaster

Severe impact damage can dislodge areas of plaster from the masonry behind, leaving a hole too big for filler to cope with. Plaster can also separate from its backing due to old age, often aided by the effects of damp or condensation. The ideal product to use to repair this kind of damage is Wickes Patching Plaster.

Start by tapping the plaster round the damaged area to see if any more sounds hollow. If it does, hack it off with a bolster chisel and hammer until you have a sound edge. Undercut it, then brush out all dust and loose debris.

Mix up a quantity of patching plaster in a bucket, to the consistency of thick porridge. Then transfer some to a hawk - a small square board with a handle fixed to its underside.

Use a garden spray gun or an old paintbrush to wet the wall and prevent suction from drying out the new plaster too quickly. Then take some plaster off your hawk with a metal plasterer's trowel and press it hard into the base of the hole. Take up more plaster as necessary, aiming to fill the hole to within about 3mm of the surface, and leave to harden.

Mix up a little more plaster to a runnier consistency and trowel it on to fill the hole flush with the surrounding plaster. Polish the surface with the trowel, spraying on a little more water if necessary to give it a smooth hard finish. Leave it to harden, then sand it with fine glasspaper if necessary to remove any nibs of plaster from the wall surface.

Using Sealants

Cracks at the wall-ceiling angle and along the join between skirtings or architraves and the walls are caused by slight movement in the house structure as temperature and humidity levels change. This movement makes hard fillers crack and fall out.

The solution is to use a non-setting mastic sealant to fill these cracks. Rake and brush out any loose material from the crack, then apply a neat bead of Wickes Decorators' Filler using a cartridge gun. Smooth off the bead with a moistened finger and leave it to skin over. You can then paint or paper over it, confident that the crack will not open up again and spoil your decorations.

Patching Plasterboard

Plasterboard is an excellent material for surfacing ceilings and timber-framed internal partition walls, but it is relatively brittle and impacts will leave a hole in the board. How you go about repairing it depends on how extensive the damage is.

For small holes - caused for example by bashing the wall with the corner of a piece of furniture when moving it - you can stick a piece of plasterboard joint tape over the repair to patch it. Use glasspaper to feather the hard edges of the tape and then skim on a very thin coat of plaster to conceal it.

If the hole is more than about 25mm across, you need a more substantial repair. Neaten the jagged edges of the hole with a sharp knife. Then cut a scrap of hardboard to a rectangular shape, longer than the hole width in one direction and a fraction narrower in the other. Make a hole in the centre, pass some string through it and knot one end.

Spread some PVA woodworking adhesive on the ends of the strip, feed it into the hole and use the string to pull it back against the inner face of the board. The adhesive will hold it in place after a few seconds of firm pressure. Leave it to set, then cut off the string.

Fill the backed hole with filler, as if you were repairing a hole in solid plaster, and sand it flush with the surrounding plasterboard.

If the board is seriously damaged - for example, by a foot slipping off a loft joist and breaking through the ceiling - you will have to patch the damage. Use a pencil and straightedge to draw two lines on the ceiling at right angles to the joist direction so they enclose the hole. Then use a padsaw to cut the plasterboard along the marked lines until you reach the adjacent joists. Mark their centre lines and use a knife to cut through the board along these lines. Pull down the severed sections of board to leave a neat rectangular hole in the ceiling.

Cut a piece of new plasterboard to fit the hole and secure it to the joists at each side with plasterboard nails. Then bed lengths of plasterboard tape over the joins using runny patching plaster as the adhesive, and skim a thin layer of plaster over the whole patch to conceal it.

Patching large holes in plaster
Use a straightedge to level plaster in a patch larger than your trowel, working it from side to side.

Patching small holes in plasterboard
Stick a hardboard offcut to the inner face of the board with PVA adhesive to support the filler.

Patching large holes in plasterboard
Cut away the damaged board to leave a rectangular hole, and nail in a patch of new plasterboard.

Wall & Ceiling Repairs - Problem Solver

Problem Areas of wall plaster are covered with a mass of hairline cracks.: Wickes Solution Working emulsion paint into the cracks when redecorating may fill them satisfactorily. If it does not, decorate the wall with Wickes Smooth Ceil to fill and conceal the cracks.
Problem The ceiling has a network of cracks which appear to follow the edges of the sheets of plasterboard used to cover it.: Wickes Solution Cover all the joint lines with plasterboard joint tape, bedded in place with some runny plaster. Feather the edges of the tape with glasspaper, then apply a thin layer of plaster over the tape. If the cracks are narrow, give the ceiling a coat of Wickes Smooth Ripple Coating or Smooth Ceil.
Problem An accident has left a small hole in an old lath-and-plaster partition wall, and some of the laths are broken.: Wickes Solution Remove loose pieces of plaster and cut away the damaged laths. Then place a piece of expanded metal mesh in the base of the hole and trowel on some Wickes Patching Plaster over it.
Problem Bags of powder filler always seem to get damp and set hard in storage.: Wickes Solution Wrap part-opened bags in polythene. As an alternative to powders, use Wickes One Time ready-mixed filler, which comes in an airtight plastic tub.
Problem A newly-plastered wall has patches of dry white powder on the surface here and there.: Wickes Solution Brush off the powder. It's called efflorescence and is the result of dissolved minerals in the water being carried to the surface, where the water evaporates and leaves the minerals behind. Decorate the wall with Wickes Paint for New Plaster, which will allow any remaining moisture in the wall to dry out.