Retaining wall cracked

ProStuart

Hi,

We had some work done in our garden back in 2021 and this included building a new retaining wall on one side.

The wall is approximately 4ft high and has been strengthened with 2 pillars (as per image).

A very heavy (750kg) masonry barbeque sits in the middle of these.

At the weekend, I noticed that a crack has appeared (as per image) - looks like it's below the top row of blocks.

Is this something I can fix myself or does the top of the wall need re-building & re-rendering by a professional?

stuart45

Can you remember exactly how it was built? 
For example, the type of blocks, how thick the wall was, were the blocks laid flat, what drainage system was used.
What's the air vent for. An air duct into the back of the fire?

ProStuart

It was breeze block I believe - they laid the first 2-3 courses flat and then single courses upright.  Drainage - you can see one of the pipes on the bottom right - there are one of these every 4-5 feet or so.  It's not an air vent - it's in-wall lighting. 

stuart45

A single skin laid upright is always likely to move on a retaining wall, even at the top. I can see the weep hole, was really thinking about how the drainage system behind the wall was done.
It's possible that the wall won't move too much more for a while and you can cut out the crack and fill it. On the other hand it might continue to move.

ProStuart

Thanks Stuart45 - logic tells me that if it's moved it'll move again so back to my original question - is there value in me lifting the marble tops, digging down behind the wall and somehow strengthening or is this something best done by someone who knows what they're doing?

stuart45

If that's a single skin of blockwork and a load of rubble or earth behind, I'd dig out down to the flat blockwork and rebuild with flat blockwork. The bed joint has been broken and the block moved out slightly, so if you are going to dig out behind you may as well knock off the top block course.

grumbler

stuart45 said:

A single skin laid upright is always likely to move on a retaining wall, even at the top.

- especially if it supports posts and a fence.