Foundation trench - Fill between trenches

[tvrulesme]

I'm building an extension (basically corridor) between my house and a detached garage I plan on converting. The trenches at 600mm wide leave just a small strip in the middle. 

 

Aside from the cost of concrete, is there any reason for this to be 2 trenches or could I just excavate the lot to the levels specified by BCO and fill the whole thing with concrete?

 

Blue lines mark the inside of the trench

 

[kandgmitchell]

Don't see why not. If the local ground conditions require a 1.0m min. dig, odds are that bit in the middle will fall over anyway. Be cautious about undermining the existing foundations of the house by digging too wide where you abut though. Is that a drain bottom right?

[tvrulesme]

10 minutes ago, kandgmitchell said:

Don't see why not. If the local ground conditions require a 1.0m min. dig, odds are that bit in the middle will fall over anyway. Be cautious about undermining the existing foundations of the house by digging too wide where you abut though. Is that a drain bottom right?

Thank you. Yes it's a drain but its temporary and will need relaying with the correct grade once concrete has been laid. Concrete will be poured to below the drain and lintel over the pipe in the blockwork

[Mr Punter]

Doing the whole thing will be easier.  Bear in mind the depth specified is from ground level, not the depth of concrete.  You may be able to just put in concrete 300 deep and build up with blockwork.

[tvrulesme]

Just now, Mr Punter said:

Doing the whole thing will be easier.  Bear in mind the depth specified is from ground level, not the depth of concrete.  You may be able to just put in concrete 300 deep and build up with blockwork.

Yes thank you. the yellow string line will be DPC so ground level 150mm below that. The concrete pavers on the left will eventually come out to drop the ground levels but are currently stopping too much collapse so will keep in place until after the pour.

 

Concrete fill depth I have is ~500mm which will bring me just below the drain. Easier than putting the drain through the concrete and putting flexible joints on either side IMO