Filling in blocks around windows

[gravelld]

We replaced our windows and had a Compriband style product applied around them. Unfortunately the windows were very tight, and some block work fell out as the old apertures were prepared.

 

The result is a couple of these:

 

And a few smaller ones too:

 

So the problems are that:

- The expanding foam tape isn't covering the gap

- There's not a solid base for re-rendering to occur

 

I have some aircrete (Toplite) and some dense concrete block and also plenty of mortar.

 

Shall I try cutting the aircrete to size and wedging it in?

[PeterW]

Need to cut a slot for the block to fit into and then peg it into the gap otherwise it will just fall out if you cram a bit in. Best to use same block type as the existing wall if possible too if it’s being re-rendered. 

[Carrerahill]

25 minutes ago, gravelld said:

We replaced our windows and had a Compriband style product applied around them. Unfortunately the windows were very tight, and some block work fell out as the old apertures were prepared.

 

The result is a couple of these:

 

And a few smaller ones too:

 

So the problems are that:

- The expanding foam tape isn't covering the gap

- There's not a solid base for re-rendering to occur

 

I have some aircrete (Toplite) and some dense concrete block and also plenty of mortar.

 

Shall I try cutting the aircrete to size and wedging it in?

A slightly different approach I used for the similar issue. I made some angle pieces in timber just slightly short of the height of the defect, clamped/jammed etc. them onto the corner and made up a concrete mix - I used some "Ciment Fondu" in the mix to speed up the setting time and trowelled it down the gap at the top occasionally tapping the form with a hammer to remove voids. At the top my mix was of a low slump that I could just trowel it into the gap and flattened it. I took the forms off before it went super hard and scratched it so the render had something to adhere to. 

 

I was really pleased with the repairs, looked smart and must have taken me about 15 minutes all in! 

[gravelld]

I think this is turning out more complicated than I thought (after discussing with another builder) and so I'm getting someone with some wet trade experience to do this! Thanks for your ideas.