Hey folks. I have just had a read through some posts about filling in large holes / gaps in walls. I am not sure what applies to my specific problem. In a nutshell: * I am currently painting my garage walls. Doesn’t have to be perfect, just neat. * But there is a large unsightly gap between the two walls in one corner. It is partially filled (badly) with mortar. See the photos below. * So I do want to spend a bit of time fixing this up to be as neat and paintable and possible. I don’t think there has been any damage to this area (it doesn’t seem to be the result of movement over time?), it looks like this was just what passed as good enough in 1974. Should I be looking at expanding foam? Maybe some fast set mortar? It is just a few cm at its widest, but the narrow void goes back a fair way in some parts. Any help is greatly appreciated.

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How to fill ugly gap in corner of Besser brick walls?

Hey folks.

I have just had a read through some posts about filling in large holes / gaps in walls. I am not sure what applies to my specific problem.

In a nutshell:

I am currently painting my garage walls. Doesn’t have to be perfect, just neat.
But there is a large unsightly gap between the two walls in one corner. It is partially filled (badly) with mortar. See the photos below.
So I do want to spend a bit of time fixing this up to be as neat and paintable and possible.

I don’t think there has been any damage to this area (it doesn’t seem to be the result of movement over time?), it looks like this was just what passed as good enough in 1974.

Should I be looking at expanding foam? Maybe some fast set mortar?

It is just a few cm at its widest, but the narrow void goes back a fair way in some parts. Any help is greatly appreciated.

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MitchellMc

Hi @OneMansFool,

I'd suggest you start by chipping out all of that degraded mortar. Take some filler rod and pack it into all the voids until you are less than 10mm from the surface. You could use expanding foam to fill the void, but it's hard to control the expansion. Next, fill the remaining 10mm of crack with Sikaflex 11FC using a sausage caulking gun. Finish flush with the surface and smooth off the 11FC using an inner cove from the silicone scraper kit. Allow five to seven days for the product to cure before painting. I'd suggest painting up to either side of it now if you wish and then coating over it after the curing period.

The Sika 11FC is a paintable and flexible polyurethane designed for joints. By using this product, you'll ensure that you don't see any cracking of the area in the future. You could use a fast-set mortar, but the flexible sealant would be my preferred method.

Please let me know if you have any questions.

Mitchell

CSParnell

Perfect advice @MitchellMc

OneMansFool

Thanks @MitchellMc + @CSParnell .

“Degraded” mortar was a good description. Large chunks of it came out with just my bare hands:

Turns out I undersold how wide the gap is: it is actually 45mm at its widest. Do you think I will still be OK to pack it with the filler rod until it is just 10mm deep and then fill it with the joint sealant?

CSParnell

Hey @OneMansFool

Given the gap has opened right up you might be better going with an option of giving the corner a spray with some expander foam to form a backing then mixing up some morter mix and apply with a corner trowel packing it in tight.

The foam you don't want a lot just enough to stop the cement mix falling through.

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OneMansFool

Brilliant, thanks.

EricL

Hi @OneMansFool

Seeing the mortar you just pulled out tells me that the person who originally filled the area did not prep the gap properly. Just to add to the suggestion made, if the expanding foam overflows from the gap, just wait for it to cure. Once it reaches its solidified state you can cut off the excess foam with a Stanley knife.

Please keep in mind that once you've finished filling the gap, you'll need a minimum of 3 weeks to let the mortar dry out. If you paint over the surface too soon moisture that's still in the mortar will push the paint off its surface causing bubbling and peeling. Getting good airflow in the area is key to getting the mortar to dry faster.

Please keep us updated with your progress, we look forward to seeing your wall gap repaired.

Eric

CSParnell

Great advice as always @EricL

OneMansFool

Hi folks, I have one more question about using the expander foam.

Note that on the other side of this wall is my neighbour’s garage. The bottom two thirds of this mortar column (while incredibly messy) is quite thick, so it forms a solid backing for me to apply the expander foam as necessary and new mortar over the top.

But the top third was complete garbage: wobbly, patchy, thin, none of it worth saving. Even if I hadn’t removed any of the mortar, expander foam would probably have ended up in my neighbour’s garage.

So after chatting to my neighbour we have agreed that I can rip out the remaining bad mortar in the top section (completely opening it up and creating a small void between our two garages) before neatening it up on BOTH sides of the wall. So I want to double check how best to do that before diving in.

Should I be aiming to create a column of expander foam in the middle of the void (marked with the question mark on the below diagram), thus forming a solid backing for the mortar from both sides? And if so, how should I go about attempting to do that — any trick to it?

Or would I be better off entirely blocking one side (somehow, with something) before using expander foam from the other?

CSParnell

Hi @OneMansFool

Just a to clarify is this a dividing wall for a duplex / town house and if so does it extend past the ceiling line through to the roof peak?

I just want to make sure it's not a dividing fire rated wall and if so fire rating motar maybe a better approach if not continue as planned.

With the major gap you maybe better packing it out with foam board if the void is that large that way you have better control and less mess.

OneMansFool

Thanks @CSParnell.

It is an internal wall separating two garages on the ground floor of a brick block – I’m beginning to think that it was originally left bare/open, and the sloppy mortar is actually from a previous reno attempt from the other side.

Thanks, I may well go the route of foam board.

MitchellMc

@CSParnell's idea of using foam board is fantastic @OneMansFool. If you have trouble sliding it in, you can cut it into smaller pieces and use the expanding foam to fill any gaps. If you pick up the standard expanding foam, it shouldn't enlarge so much that it comes out on the neighbour's side.

To use the expanding foam by itself, I'd suggest the triple-expanding version and run a continuous bead down the middle of the wall. You'll find it only expands several centimetres in either direction and shouldn't reach the surface of the gap in either of your properties. You'll likely need to come back and do another bead on either side to reach just below the surface of the gap.

I like the foam board idea, and it would be my first choice if you can get it to fit.

Mitchell

OneMansFool

Progress update: it’s going great! It’ll look good when done.

Hardest part is getting the consistency of the mortar correct, but that is easily corrected as you go.

CSParnell

Hey @OneMansFool looking great looking forward to hearing the methods you went with and seeing the final results

OneMansFool

I filled most of the void with the foam board before setting it in place with expanding foam.

It turned out tidier than I was fearing it would:

I did the mortaring in two goes, the bottom bit a few days ago and the top bit just now. Really happy with how it turned out, and in a month or so I’ll finish the undercoat:

CSParnell

Fantastic @OneMansFool looks great so happy it turned out as well as it has for you. Well done.

EricL

Hello @OneMansFool

Thank you very much for posting those photo updates, your repair work looks excellent. Your strategy to do it in sections is exactly the right way to go about it. This means that you've allowed the moisture to escape before putting the next section on. However, I still recommend waiting to make sure the concrete is fully cured before painting the surface.

We look forward to seeing your next project.

Eric

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