Excavation near footings of an existing wall

[1DIYRichardHead77]

I am excavating my rear garden as a part of a landscaping project and I am trying to establish how close I can excavate near to an existing garden wall. The existing garden wall is 1 brick thick with a 6 brick pillar at either end. Its about 7.6' tall and runs the length of my garden 65'). The wall is built on concreate foundations which sits and clay soil. I don't know how deep the footing are under the wall but the wall was built when the estate was developed.

I would like to lower the level of my garden by approx 900mm that runs up to the wall. To avoid undermining the footings I would propose to leave say 750mm of clay/soil untouched directly in front of the wall along the entire length and then build a block wall in front of it with a a single brick facade in front of that as a retainer for the border.

Is the 750mm of untouched soil in front of the wall sufficient to save the integrity of the existing wall? I have heard of the law of repose but I can find and clear guidance.

Also my proposed block wall with single brick facade in front of it, will this be substantially weaker to retain the 900/1100mm of earth behind it than a single brick solid wall?

Comments appreciated

Thanks
Rich

 

[noseall]

not a problem. 750mm is a good distance away.

as a fail-safe, you could always sprag the wall as you dig back. put a vertical batten up the wall and wedge a prop against it. the prop could be dug into the ground at the low end.

we dug out a 1m dig foundation, right along side some existing shallow strip footings of a neighbouring two storey semi!

not even a murmur.

i was mighty relieved when the concrete went in though.

 

[1DIYRichardHead77]

not a problem. 750mm is a good distance away.

as a fail-safe, you could always sprag the wall as you dig back. put a vertical batten up the wall and wedge a prop against it. the prop could be dug into the ground at the low end.

we dug out a 1m dig foundation, right along side some existing shallow strip footings of a neighbouring two storey semi!

not even a murmur.

i was mighty relieved when the concrete went in though.

Thanks Noseal, much appreciated,

What do you recon in terms of the wall construction? I want to cut cost by incorporating one leaf of medium density block with a single facing brick facade but I cant help but think this wont be as strong as a single brick think solid wall?

Rich

 

[Shytalkz]

we dug out a 1m dig foundation, right along side some existing shallow strip footings of a neighbouring two storey semi!

not even a murmur.

i was mighty relieved when the concrete went in though.

I hope you don't make a habit of that, Nose! Sometimes it works; sometimes it doesn't...

 

[noseall]

no problem with backing in with block but use 7n solids.

 

[noseall]

we dug out a 1m dig foundation, right along side some existing shallow strip footings of a neighbouring two storey semi!

not even a murmur.

i was mighty relieved when the concrete went in though.

I hope you don't make a habit of that, Nose! Sometimes it works; sometimes it doesn't...

no most definitely not!

the area was sheltered and the substrate was very good. also, the n'bours strip footing contained re-bar and was decent thickness. i still lost sleep though.

 

[1DIYRichardHead77]

no problem with backing in with block but use 7n solids.

Thanks again

 

[Shytalkz]

no most definitely not!

the area was sheltered and the substrate was very good. also, the n'bours strip footing contained re-bar and was decent thickness. i still lost sleep though.

Like I can talk - pulled some footings on my barn a few weeks ago, hit a soft spot in a trench running 500 away from and parallel with an existing very ropey brick and flint wall (which is going to be demolished at some stage) with its foundations at strip level.

Ended up going 1800 deep, no shoring, on site on my own clearing out the bottom, excavation side on ex wall side starting to belly; wall moved, as shown by development of vertical crack...

Forgot to order concrete next day (it's an easy thing to do!), finally concreted 48 hours later. Early hours of the following night, the earthquake struck! However, the wall stayed up, got away with it, but Iwould have gone mad if I'd seen builders doing the self same thing on any of my "proper" jobs

But, I was very, very wary, working under that lot...and it was very stupid, it's not as if I could plead ignorance!