How to repair cracked brick retaining wall?

Question

Hi,

I have a couple of locations that need maintenance/repair.

One is a natural sandstone rock outcrop that is subject to the weather and is crumbling and turning to sand - very slowly. The large rocks you see in the photo are not from the outcrop, but the tiny ons are! One section gets damp and has some moss and ferns growing on it. How do I stop this? Can it be sealed or faced?

The other is a sandstone wall which was built but is developing a bit of a gap. How do I arrest this?

The third is a brick wall that has a large gap opening. How do I repair and maintain this? Should a put a strap from one corner to the other? Is there 'concrete glue' I can use? I would also like to paint/face this to look more like the sandstone around it.

I'm sure there are products out there for all of these problems - just need some help to find them!

Photos attached.

THANK YOU!

TedBear · Answer

The first two issues both look like they are caused by  a lack of proper footings.

You can see that the stone wall has dropped toward the rear where it cracks.  Having thickness, it may not drop any more, but I would keep plant roots away from it. You will probably get away with adding motor to fill the crack.   To make it stronger, I would dig a hole at least 400mm down into the soil on the inside and mortar some bricks (or stone) across the gap to brace it. When filled back in the bracing will be out of sight.

For the brick wall, I suspect, as others have said, that the plant roots have grown thick and are pushing the wall down the hill.

The best repair would be to dig the plants and the soil out, get (or hire) a long lever and see if you can lift the bottom wall up a little to get it back into place.

Alternatively, you could bolt a length of timber along the lower wall (about 300-400mm up) and use 2 or more bottle jacks under that timber to lift the wall.

If you can do that, then shove some concrete into the new gap under the wall and let it set before removing the lever/s or jacks.

Then, as for the stone wall, build a brick pier inside the wall across the crack, but full height of the wall. Make sure that you put some footings under the pier to help keep the wall from subsiding again. That way all repairs are out of sight, so even if you are a messy brick layer, it doesn't matter as long as it bonds strongly.

Dave-1 · Answer

Afternoon @su51q

The strapping will only be as strong as the mortar that is holding the bricks together. It may create a new crack/s if you fasten a strap along it.

I dont think bondcrete will be able to hold the two sections together, with strapping it may look like its holding but I wouldnt be confidant.

Dave

MitchellMc · Answer

The strapping could work @su51q, but it's problematic to give bandaid advice on a structural issue. You could potentially stitch the gap with the strapping. It would need to extend at least 1000mm past the gap on either side. You would have to use Ankascrews to fix the strapping to the bricks on either side and at several locations. To install the Ankascrews, you would need to pre-drill the strapping and the bricks. This could potentially stop it progressing, or it might just cause the wall to separate further along. To install the Ankascrews, you would need to pre-drill the strapping and the bricks.

Boncrete is an adhesion promoter, but it's not a glue in the sense that it can hold things together. Even a construction adhesive would be no match for the physical forces at play here, which have caused that large a section of wall to subside and break away from the rest.

Mitchell