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Digging up the concrete oversite


WWilts

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New build with trench fill footings. Hardcore, sand blinding, DPM, 100mm concrete.

If a block wall with foundations is in the wrong place, one option is to dig up the concrete oversite & move the wall to the right place.

Are there any disadvantages to digging it up and relaying the hardcore + concrete (apart from time & cost)? Might there be a less sound structure in some way? 

Not going to dig it up, just want to be informed for giving the builder a talking to.

 

Edited by WWilts
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Nothing wrong with digging out and digging again on the right line, strip footings should only be taking vertical loads so not relying on sideways compressive strength of soil etc.

Moving a trench into previous backfill is a big no-no and you would need to increase depth of trench to get back to solid ground

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35 minutes ago, markc said:

Nothing wrong with digging out and digging again on the right line,

More advanced stage than that unfortunately, DPM & concrete slab already in place, block wall going down to trench fill footings already in place (just slightly wrong place).

Earlier hesitation to dig up the (nice) slab was due to fear that the repaired slab might not be as sound. Any basis for that fear?

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9 hours ago, WWilts said:

More advanced stage than that unfortunately, DPM & concrete slab already in place, block wall going down to trench fill footings already in place (just slightly wrong place).

Earlier hesitation to dig up the (nice) slab was due to fear that the repaired slab might not be as sound. Any basis for that fear?

Breaking/digging up a slab is never going to be great, much better to get around the problem with additional above ground works if the slab/DPM/insulation is all good

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3 hours ago, Dave Jones said:

is the wall structural ?

 

Could get over it with a steel ?

Yes, structural spine wall.
Steel might well have worked if we had thought of it at the time.
First floor joists in & build now done up to roof trusses.

Given that we are stuck with the slightly off-position structural wall, we merely want to demonstrate to the builder that we are being exceptionally good to him by adjusting everything to accommodate his error in setting out the structural wall. This might encourage him to do his best for us in every other respect.

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46 minutes ago, Mr Punter said:

How far off is the wall?

160mm. Had to adjust a staircase position accordingly, and to lose a bit of floor space from an inner storage-type room.

Builder was responsible for setting out, and acknowledged his error. But now says that digging out the structural wall down through the concrete slab and all the way to the footings would not have reduced the quality of the concrete slab. At the time we clients judged that there was a risk of the digging up reducing the quality of the concrete slab. We chose to adjust everything to accommodate his error. That saved him a fair bit of expense. Now just want to put things in the right perspective with him: we have gone out of our way to be good to him. So it would be good if he keeps doing his best for us.

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The builder is talking crap, no way would they be able to do that and get the same compaction and layer to match the original.

you have made sacrifices to accommodate their error, instead of money changing hands go for something additional as compensation, patio, landscaping etc.

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As you are about to put roof trusses on it is a bit late to be bringing this up and all talk of ripping out the foundations is fanciful.  It does not sound like the 160mm made much difference.  If it is an internal wall I assume you gained a bit of space in one room and lost it in another.  If you harp on about this you will just piss off the builder.

 

Just try to keep the job moving and try to make sure you spot any further cock-ups early on.  At best, do like @markc says and see if you can get some extras included.

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15 hours ago, markc said:

Oh no! How come?

We had the first Isoquick foundation installed in the UK back in 2010. It all went well until the concrete was poured. Unfortunately the concrete laying did not go so well. A combination of cost cutting, by not using a pump, and the concrete setting too quickly left large voids in the 200mm slab which were detected using ultrasonic testing. The results were confirmed by drilling core samples. Fortunately we videoed the whole procedure and had the evidence to show to the boss of the company. The result of the farce was that the whole system was cut up using a diamond road cutter and taken away. The second time around it all went smoothly fortunately.

 

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Videography,  the one essential service for every single self build.

 

 

A time lapse camera will do: costs £100 and a bit of effort.  2 cameras are even better.  Just one saved us £8000.

 

Unless the owner is onsite every day, knows and understands whats going on, it's madness not to record what's happening day to day. 

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On 11/02/2022 at 11:02, Mr Punter said:

As you are about to put roof trusses on it is a bit late to be bringing this up and all talk of ripping out the foundations is fanciful.  It does not sound like the 160mm made much difference.  If it is an internal wall I assume you gained a bit of space in one room and lost it in another.  If you harp on about this you will just piss off the builder.

 

Just try to keep the job moving and try to make sure you spot any further cock-ups early on.  At best, do like @markc says and see if you can get some extras included.

As Mr P says you are just going to have to suck it up mate.  If it is of any consolation the same thing happened to me -;the OCD Mrs came up with an idea to move a major waĺl 300mm which happened on the above ground drawings but wasn't reflected in the foundation plan. I am delighted.  Secretly.

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