Trench Fill or Strip Foundation?

Joined
23 Oct 2016
Messages
24
Reaction score
0
Country
United Kingdom
Hi all,

I'm shortly going to embark on my rear extension project. Did my own designs and drawings and full plans approval granted by building control which I'm pretty chuffed about, but I'm by no means an expert!!

The plan was, after digging a test hole before submitting plans and speaking with the BCO, to match the depth and type of the existing house (end of terrace built 1995 house). Trench depth is 1250mm below ground level, 250mm strip footing and then trench block and normal blocks up to ground level.

Access is a pain as were the corner plot in a cul de sac and I've uploaded a picture for reference.

The original plan was to have 1.7m3 of concrete delivered and my brother and dad would provide help barrowing it round the back of the house. Social distancing has put a spanner in the works for this. So I'm now considering trench filling up to below the last couple of block courses below DPC. This would mean just over 6m3 of concrete which I could get pumped.

Costs for the original strip footing plan were £290 ready-mix, £350 in trench blocks and at least £350 (2 blokes at £175 a day) labour to lay the trench blocks plus about £60 quid sand and cement.

Now, I need to call to get a price on Monday for the 6m3 and pump, but I can't think that the cost will be too much different.

What's everyone's thoughts? Obviously need to check with BCO that changing the trench fill is acceptable, but does this seem like a sensible solution? No barrowing, less faff for the brick layer.

Cheers!
 

Attachments

  • 20200502_212639.jpg
    20200502_212639.jpg
    451.3 KB · Views: 291
Sponsored Links
Joined
23 Oct 2016
Messages
24
Reaction score
0
Country
United Kingdom

TRENCH FILL ALL DAY AND TWICE ON SUNDAYS!

Good enough?

A popular choice then! :) wish we have Mixamate round here, that looks like a very neat set up with the mixing and pump all done from one truck.
 
Joined
2 Feb 2006
Messages
45,709
Reaction score
3,169
Location
Staffordshire
Country
United Kingdom
A popular choice then! :) wish we have Mixamate round here, that looks like a very neat set up with the mixing and pump all done from one truck.
We are lucky to have a local family run business that provides both gauged concrete and a pump - something that the trade has been longing for, for decades.

There are scenarios where strip foundations over rule mass fill, but they are rare.
 
Sponsored Links
Joined
23 Oct 2016
Messages
24
Reaction score
0
Country
United Kingdom
Hi all,

Thanks for your comments. Just thought I'd update this. Having spoke with Building Control they've given the go ahead for trench filling too.

Good thing about this is that they have said the trenches only need to be 450mm wide instead of 600mm for the strip footings so less to dig out by hand and less to get rid of, although less shoulder room at deeper depths. But this translates to less soil to dispose of, proportionally less concrete when comparing the two methods, less money on blocks, less bricky labour less sand and cement for mortar. Even factoring in the £400 for the pump hire, all being well, the cost to get to DPC level will now be about £200 less than planned, although I'm sure something will crop up to spend this money on!

Thanks for the help and hope the above info is useful for someone in the same boat down the line!
 
Joined
11 Apr 2006
Messages
2,147
Reaction score
200
Location
Berkshire
Country
United Kingdom
Agree with all of the above, plus there is nothing more back breaking and miserable than laying blocks in a trench below ground level.
 
Joined
11 Apr 2006
Messages
2,147
Reaction score
200
Location
Berkshire
Country
United Kingdom
We are lucky to have a local family run business that provides both gauged concrete and a pump - something that the trade has been longing for, for decades.

That's going to be the future if they've managed to do it without reducing the capacity of the truck too much. How many cubes can they carry?
 

bsr

Joined
5 Aug 2008
Messages
695
Reaction score
61
Location
Gloucestershire
Country
United Kingdom
Is it normal, that a trench fill can be narrower than a strip? Surely the limiting factor is the beating capacity of the soil below, which is the same in either case.
 
Joined
26 Aug 2016
Messages
6,609
Reaction score
939
Country
United Kingdom
The bearing capacity of the soil can't be that limiting, we had most of the back upstairs of the house supported on a 600x600 square pad with a column built off it.
I understood the width and flat bottom of foundations is more to do with stability, you don't want them rolling over in the ground.
Any concerns and a structural engineer can calculate, as they did for our pad.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Top