Trench fill depth and vibration for air

[LSB]

Taking cost out of the equation knowing it's way more expensive.

 

If we have a trench of 1m depth as specified by the SE, to make things quicker for slow DIY self builder is it going to cause any issues getting the concrete trench filled to 775m, i.e. 1 block below ground level.

This particular length is 24m, 18m turning to 6m so L shape.

I assume this will need vibrating, is this going to work with concrete of 3/4 m deep or is there a different mix that will sink without air holes, drying time isn't a particular issue as lots of other things to get on with.

 

What is the minimum and maximum concrete depth you can lay to build a wall on.

On the back wall of the build our SE has specified a depth of 2.4m for wall of 24m where a corner approx. 6m * 6m which 'may' be clay, but has said that BC have final decision about depth for different parts of the wall.

The field behind that side, which is 3m higher, has large patches of clay hence this assumption and a geological ? (can't remember the proper term) survey/map showing lines of clay in the area.

 

I'm hoping we can use step foundations for the back wall as the whole wall is 24m long so we don't want to do 2.4 for the whole lot just to make the bottom level.  I've seen some pictures of those in some blogs on this site, bit dangerous due to possible collapse.  How does laying the concrete work on this.

The soil along that wall is thought to be 6m clay, 12m loam, 6m sand / loam all with some gravel mixed in.

As a brownfield barn conversion site it's difficult to really see what's there.

 

TIA

 

 

[twice round the block]

Have you had a detailed soil survey done on this plot ?

[LSB]

2 minutes ago, twice round the block said:

Have you had a detailed soil survey done on this plot ?

We had a soil contamination survey where they did 4 trial holes, but that was looking for contamination as it was a conversion, there was also movement trials which were inspected monthly for 3 months, no movement found.

 

The SE that did the original survey to check the barn was strong enough to convert also did some trial holes (3) to check the depth of the existing foundations, but he just said that it was fine although it would need some underpinning, this was an individual small company.

 

The SE that did the contamination then did the full structural drawings, but as they had been to site already they didn't come back and just looked at studies and what they already had, despite us asking them to come out.

 

We dug a trial trench the whole length of the 24m wall which is where the measurements of soil type come from and sent this to the SE and he just said, ask building control.

 

The barn had 3 walls so the 4th side is simple as it's new and is what we are building now.  This is the one where we have the question about depth of concrete and vibration.

 

 

[twice round the block]

It's down to building control the depth you excavate too, and the concrete and blockwork that goes in. 

They're the ones that have to sign it off before you can go any further with the build

[Mr Punter]

You would normally just tamp the foundation concrete with a rake. No need to vibrate.  There is no problem having steps in the foundation.  You can build on 300mm depth concrete as long as it is far enough below ground so the bottom is protected from frost.  Depends on ground conditions.

 

Definitely leave at least 225 bgl.  May need to be lower for drainage etc.