How to repair a rendered wall

Nailbag

Difficulty: Beginner

Repairing a rendered wall is an easy D.I.Y. project that can improve its appearance and extend its life. By addressing chips, cracks and other damage, you can maintain the wall’s durability and ensure it looks great for years to come.

Steps

Step 1

Clean and prepare the wall.

For small to medium chips, use a metal putty knife to scrape away loose material. Follow with a wire brush to smooth the edges. For larger chips, remove additional degraded or loose render around the edges to provide a better base for the filler.

For fine cracks, use the edge of the metal putty knife to widen them slightly, remove loose pieces, and smooth the edges with a wire brush.

If a corner edge is damaged, straighten it by gently tapping it back into place with a hammer and punch.

A small blower can help remove debris from hard-to-reach spots.

Finally, clean the area with undiluted Sugar Soap to remove dirt, oil or mould. Rinse thoroughly with clean water and let it dry completely.

1.1 Remove loose material - large area.jpg 1.2 Use a wire brush - large area.jpg 1.3 Open up fine crack.jpg 1.4 Brush smooth fine crack.jpg 1.5 Using a punch to straightend edge.jpg 1.6 Use a blower to clean hard to reach.jpg 1.7 Clean with Sugar Soap.jpg

Step 2

Fill minor cracks.

To repair cracks between 3mm and 4mm, load your Sikaflex 11FC into a silicone gun. Cut the nozzle at a slight angle to match the crack's width.

Apply the sealant into the crack, ensuring it fills completely by moving the nozzle along the length of the crack and slightly overfilling. Use a putty knife or small trowel to smooth the surface of the sealant, working from the centre outwards to blend it with the surrounding render. Feather the edges to create a seamless transition between the filled area and the existing wall.

Before the sealant cures, clean any excess with a damp cloth or sponge to ensure a tidy finish. Allow the sealant to cure according to the manufacturer’s instructions (typically 2-3 hours for initial curing, though full curing may take longer).

2.1 Minor 3mm crack.jpeg 2.2 Minor crack clean.jpeg 2.3 Minor crack silicone.jpeg 2.4 Siliconed minor crack.jpeg

Step 3

Repair larger cracks and damage.

To repair larger cracks and damage, use Polyfilla Exterior Brick & Render, which is ready to use and dries with a rendered finish.

Apply the filler with a filling knife or pointed trowel, feathering the edges to blend with the existing render. For a smoother finish, take a damp coarse sponge and gently rub it over the filled area in a circular motion. Start from the centre of the patch and move outward to help blend the edges seamlessly into the surrounding surface.

Rinse the sponge regularly to avoid adding more filler to the area. This will help achieve a smooth, even texture.

For corners, use painter’s tape to protect adjacent areas and remove it promptly to avoid residue.

An old toothbrush or damp cloth can be used to add additional stippling and texture to your repaired area.

Clean your tools and allow the filler to dry completely. Drying time varies by product and conditions (typically 2-3 hours for 2mm repairs and over 16 hours for 10mm repairs). Always follow the manufacturer’s instructions.

3.1 Filling with small trowel.jpeg 3.2 Filling with filling knife.jpeg 3.3 Feathering out.png 3.4 Taped edge.jpg 3.5 Filling edge.jpg 3.6 Filling other side of edge.jpg 3.7 Allow to dry fully.jpeg 3.8 Clean tools.png

Step 4

Apply primer over the repair.

Apply a high-quality 3-in-1 exterior primer to prevent the grey filler from bleeding through and to ensure good adhesion of your paint. If the filler remains visible after the first coat of primer is dry you should apply a second coat, particularly when using lighter colours.

4.1 Applying primer.jpeg 4.2 Applying primer over silicone.jpeg 4.3 Primer second coat.jpeg

Step 5

Paint over the repair.

To match your existing colour, a sample can be taken into your nearest Bunnings store. Downpipe straps are easy to remove and can be used to colour match if they are the same colour as your render.

Apply two coats of your exterior paint, allowing the first coat to dry fully before applying the second.

Please note that new paint may not blend perfectly with older areas immediately. For the best results, consider painting the entire area to ensure a consistent finish. If blending is necessary, allow the repair to weather for a short time, then assess whether touch-ups or a complete repaint are needed for an even look.

5.1 Removing strap to match colour.jpeg 5.2 Match colour strap.jpeg 5.3 Colour sample chips.jpeg 5.4 Painting with colour.jpeg 5.5 Completed edge.jpg 5.6 Completed wall.jpg