How to fix large gap in render on brick wall?

Question

Hi. I need to render this narrow section of garage brick wall where an extending wall has been removed. Once rendered I'll need to be able to bolt a fence post to it. I've done a bit of basic rendering before but this bit of wall has some bigger gaps and holes. Any advice on getting the tender to stick in place? Should I do filling first then top coat? I guess it will need to be pretty thick so as not to slump? I will be moving the small column water tank but the larger one (neighbours) is staying put.

Cheers

MitchellMc · Answer

Welcome to the Bunnings Workshop community @shredded. It's wonderful to have you join us and many thanks for your question on repairing a rendered wall.

For a repair like this, I'd tackle it in a few stages rather than trying to apply one thick coat. Start by thoroughly cleaning the wall and removing any loose mortar, dust or debris. You can then use a mortar repair mix to fill the deeper voids and larger gaps first. Wet the voids down with a spray bottle of water and then pack the mortar firmly into the holes and allow it to firm up before applying additional layers if needed. For the areas where your fixings will be located, you should consider using

https://www.bunnings.com.au/sika-20kg-sika-monotop-352nfg-structural-repair-mortar_p0760433

as it would be better suited to taking a structural fixing.

Once the deeper repairs have cured, continue building the area out with additional mortar coats until you're within around 5–10mm of the finished surface. Working in multiple coats helps prevent slumping and allows you to use a workable mix rather than having to make it excessively dry, which can affect adhesion and strength.

After you've brought the surface close to level, switch to a render mix for the final coats. This will make it much easier to achieve a smooth, consistent finish that matches the surrounding wall.

Given you'll be mounting a fence post to the wall later, I'd make sure any larger voids are well-packed and fully cured before drilling and fixing into the masonry. The structural fixing should ultimately be anchored into the brickwork rather than relying on the render layer itself. Given the lack of solid bricks in that vicinity, I'd consider concreting your post in the ground as well.

Here's a helpful guide: How to render.

Please let me know if you have any questions.

Mitchell

R4addZ · Answer

Hi @shredded

I would firstly be concerned about what you will be anchoring the fence post to as that brickwork looks pretty scrappy. It may be worth getting a structural engineer in before rendering it so he can see what the wall is actually like. There also looks to be a bow in the wall by looking at the corner of the wall to the left.