Erosion of slab foundations

[Oliver Dawson]

Hi I dug out some soil a couple of years ago to level off and put a wooden structure along this wall. I’ve removed the structure and the foundations of the concrete slab has eroded.

I want to put a wooden planter along the wall so the look is not a concern. But I do want it to be fixed so I get a good night’s sleep!

I’m a handyman with basic bricklaying and competent carpentry. What are my options? And how would I do it? Or is this something I need to outsource?

Thanks

 

[johnny2007]

How the hell is that happened???
Was it nosef@ckall who built that?

 

[stevie888]

That's crushed concrete under the wall foundation which is now not retained and is moving.

Eventually the wall will fail. You need to put up a shutter and cast some sort of an edge restraint to stop any more coming away.

 

[johnny2007]

I bet they used little cement and added polystyrene to the mix.

 

[noseall]

I’m a handyman with basic bricklaying and competent carpentry. What are my options?

Don't sneeze.

The slab looks chunky enough, but the friable ground beneath needs stabilizing. As said - an ugly shutter and poured concrete or a secondary wall built in front of the slab toe.

 

[Deleted member 323070]

As Stevie and Noseall suggested, you need some way to stabilise it.
It looks to me as though there was about 100mm of crushed concrete, which in that situation is little better than MOT type 1 or 2.
Then a 50 mm layer of concrete laid on top.

If you're going to provide a shutter for new concrete, it needs to allow sufficient thickness of concrete to provide a good edge restraint to the crushed concrete.
So, IMO, the shuttering should be set at a bare minimum of 50mm away from the existing edge of the good concrete. And a high slump value mix of concrete used to allow the voids to be filled. If anyone, with more experience, suggested more than a thickness of 50mm, I would be quite happy with that.
If the shuttering came to the top of the good concrete layer, it would probably pass as "like it always was", after a time for weathering.

 

[Oliver Dawson]

Thanks all. Would you dig out any of the loose stuff before adding concrete? Would I need to get the concrete piped in or could I hire/borrow a concrete mixer?

 

[Deleted member 323070]

Thanks all. Would you dig out any of the loose stuff before adding concrete? Would I need to get the concrete piped in or could I hire/borrow a concrete mixer?

The idea of having sufficient thickness of new concrete is to stabilise what is there. It will become incorporated with the loose stuff, especially if the concrete is a high slump mix.
How you get the concrete depends on the volume.
I would suggest that less than 1 M³ can be mixed on site easy enough with a hired mixer. But piped in is so easy and quick.

It's not easy to estimate how much you need.
Assuming you have shuttering 200mm deep, and 50mm away from the good concrete at the top, and the depth into the loose stuff is about 100mm, I'd estimate about 1.75 M³ for each 100 metres run.
Thus if you have a 25 metre run of those dimensions, you're looking at about less than 0.5M³

 

[Oliver Dawson]

Hi mate this is great info. Thank you very much!