Trench for foundations for a retaining wall: Need to be cut below the surface?

[DIYalot]

Hi. Is it a requrement that the trench for concrete foundations, for a retaining wall, needs to be cut below the ground surface? I mean the lower ground surface. A retaining wall that might be 8 foot high from my side is going to be built by my neighbour, but the bottom of the foundations when they are in, will be at my (lower) ground level. In the end it's like there will be an open trench when the foundations are in. Open at my side. Should I be worried basically? Thanks.

 

[jj4091]

I was told the other day that relating walls need to use Rebar baskets and rods and be larger than a normal footing. Can't provide any dimensions though, but I suppose it depends on the height and length of the wall.

 

[Dereekoo]

If its been designed to take into account the allowable ground bearing pressure that the founds are resting and all the other intricacies of retaining wall design then no, but it all depends if it has been designed or a finger in the air guess. It could fail by overturning or slippage or collapse or not fail at all

 

[DIYalot]

What I have done is contact the case worker in local council planning, dealing with the building application. The application does not mention a retaining wall, only construction work related to the house on the property. Like this wall is the biggest safety issue, but it's not officially on the radar of planning dept. I guess if planning are OK with the picture I sent them, then there is no problem. I suppose, they might make enquiries. What bothers me is the height of it from my side. It will be an 8 foot wall from my side. That's a tall retaining wall. Althought it's only retaining about 4 foot of soil.

 

[Deluks]

The other issue is drainage.
When water backs up behind that wall after excessive periods of rain, where will it go?
A common solution is to put pipes or drainage holes in the wall, but that means the water will discharge onto your land, which you don't want.

 

[jj4091]

What I have done is contact the case worker in local council planning, dealing with the building application. The application does not mention a retaining wall, only construction work related to the house on the property.

If it has not got planning consent then I would have thought it will not be inspected as part of the building regulations either I would ensure the building inspectors are contacted directly and not rely on a "case worker ", what ever that is, to do it.

 

[Dereekoo]

The other issue is drainage.
When water backs up behind that wall after excessive periods of rain, where will it go?
A common solution is to put pipes or drainage holes in the wall, but that means the water will discharge onto your land, which you don't want.

Part and parcel of the design process

 

[DIYalot]

I got back to the case worker and CC'd to Building Control.

 

[Odds]

I'd dig a 3' trench to support an 8' wall but if the bottom of the trench is level with your garden then another foot wouldn't hurt, would it? Have a word with your neighbour and explain it from your pov.