How To Repair Cracks and Holes in Walls

Posted on 22/09/21

Wall Prep


Most properties are built from a blend of bricks, concrete blocks and timber frames. While older homes might be made from natural stone, the construction of a property depends on whether the walls are internal or external, and whether they’re designed to be supporting walls or non-load bearing.

Repairing cracks and holes in the walls depends on where they’re located and the material they’re made from – here’s our guide on repairing these signs of damage properly.

First Up - External or Internal?

External walls are load bearing, meaning they support the weight of the rest of the property, such as the floors and roofing. They’re typically made from stronger, more durable materials as a result. Solid external walls, made from stone or brick, are common in properties built prior to the 1920s. These walls are often at least 225mm thick, whereas modern properties are built from concrete blocks.

Cavity external walls are also common features of modern homes, having been constructed with a cavity in the middle. The walls are each around 100mm thick and separated by at least 50mm in gap, with metal wall ties tying them together for stability. These walls are made from timber, concrete blocks or bricks, and are popular for their ability to prevent moisture and heat loss. They can also be combined with insulation for greater energy efficiency.

Internal walls are either party walls or partition walls. Party walls are those which are used in shared walls, such as between a semi-detached property or terraced homes, while partition walls divide up the floor space into separate rooms. They can be made from stone, brick or concrete blocks, or plasterboard fixed to frames of timber or metal. While they’re not usually load-bearing, internal walls aren’t always non-load bearing, so it’s important to check beforehand.

Repairing Plasterboard

If there are holes or cracks in plasterboard, you can usually repair them fairly easily. However, if the hole is larger than 125mm, you’ll probably need to fit a plasterboard patch into the space to give the filler something to adhere to. For larger cracks, you may need to build up several coats of filler rather than applying one thicker layer, so that it fully dries.

There are several types of filler for this job, from fast-drying fillers that will set within around 20 minutes to interior general-purpose filler and fine-surface filler that has an ultra-smooth finish.

Load some of the filler onto a filling knife and draw it across the hole at a right angle, pressing it in firmly so that the filler comes over the surface just slightly. It can then be smoothed down using a sanding block or sandpaper when it’s fully dry.

Patching Corners

Corners can be particularly vulnerable to wear and tear, so there’s a high chance you’ll need to patch a corner at some point, in order to maintain the look of your home. You can either repair the damage to a corner of a wall with undercoat plaster, using a piece of board fixed to the wall for a neater finish, or you can reinforce the corner with metal or plastic corner beading.

The latter can be cut to length and affixed to the wall with a plaster undercoat, smoothing the plaster into the area with a trowel. Press the beading into position and build up the plaster, then scrape it back until it’s level with the existing surface. Once dried, apply metal primer over the corner before decorating to prevent rust coming through later on.

Lath and Plaster Repairs

Providing the laths are secure, small holes can be filled in the same way as with ordinary plaster. Broken laths can be the reason that plaster begins to crumble – if this has already happened, you’ll need to reinforce them with metal mesh under the new plaster.

Remove any crumbling plaster until you reach the edge where the plaster is secure and attached to the laths. Cut a piece of mesh that’s the size of the hole, fixing it in place with plaster undercoat around the edges. Don’t nail or staple the mesh in place, as this could cause additional damage to the existing plaster.

Dampen the laths and apply the plaster undercoat with a plasterer’s trowel, forcing it between the laths so that it’s securely fixed in place. Score the surface to create a diamond pattern, rough enough for the finishing coat. Let this layer fully dry before applying a finishing coat of plaster.

Final Thoughts

Maintaining your home often means dealing with small holes or damage to your walls before it develops and becomes a bigger problem. By staying on top of any small repairs like cracks in the plasterboard or holes in your walls, you can ensure your home is safe, secure and looks great for years to come.

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