How to fill the brick cavity gap for rendering?

[Shu889]

I removed a mental concrete filled interior door jamb. Now I need to fill the exposed double brick cavity and make the surface flush. Any suggestions on best way to do without reducing height and width of the opening? 

Thanks   

[MitchellMc]

Welcome to the Bunnings Workshop community @Shu889. It's fabulous to have you join us, and many thanks for your question about filling a gap.

You can fill the large gap with mortar using a pointing trowel, and once dry, apply a render over it with a finishing trowel to smooth the area. You might like to spray some expanding foam in there first to help prevent your mortar from falling into the wall cavity.

Here's a helpful guide: How to render. 

The render will leave a textured finish. So, if you were after something you can sand smooth, you might like to skimcoat it with Gyprock CSR 15kg Easy Flow All Purpose Compound.

Remember your PPE, including a face mask, safety glasses and gloves.

As a word of caution, I just wanted to check that you haven't removed bricks in that area. I note the steel lintel above the area, and I have concerns that if you had widened the opening, you could have comprised the lintel's support. Say if you removed half a brick to widen the opening, the lintel might now just be barely wider than the gap and holding on. This could cause it to fail and drop. If you have removed bricks, I'd encourage you to enlist the services of a professional to assess the situation before continuing.

Please let me know if you have any questions.

Mitchell
 

[Shu889]

Thanks Mitchell. 

No, I didnt touched the brick and the structure. I only removed door jamb and the mortar they used the fill the hollow jamb frame. 

Would I be able to render directly over the expansion foam? I am thinking to fill the cavity with expansion foam. Trim it flush with the rendered side. On the exposed brick, I will follow your recommendation to mortar, then render. Would that work? If so, any recommendations on which expansion foam to buy? 

[MitchellMc]

I'd rather have a solid mortar under the render than just expansion foam @Shu889. Say you used expansion foam and then a 10mm layer of render directly over, if someone were to press on the render, the expansion foam underneath would flex and the render crack.

This expanding foam would be suitable to use.

Mitchell

[Shu889]

Cheers. Will give this a go. Some foam in the cavity. Then 10 mm mortar over the cavity and exposed brick. 10mm of render. Then finish with 3-5mm of top coat.