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Part 5 - Foundations started

Stones

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NEW ENTRY

 

4 weeks after we hoped to have it, our warrant was finally approved.  Another weeks delay waiting for the digger driver, but finally work has started in earnest on site.

 

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Strip foundations were dug and concrete poured the following day.  A minor set-back during the pour, a hydraulic line split on the mixer forcing it to shut down.  An hour later after the mechanic had brought out and fitted a new line, the job was finished. 

 

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You’ll note the lack of a digger on the concrete pour. 4 men - 2 on barrows,1 spreading in the trench, 1 tamping and levelling the concrete off.  It’s the fastest I’ve seen strip foundations poured. 

Having finished the pour, the concrete was floated to a smooth finish.  Not normally required with block foundations but as we are building with ICF, it’s important in ensuring that the base blocks are level.

The ICF (Amvic) system blocks that we are using are formed from two sections of 65mm EPS separated by 150mm plastic webs to form a hollow core for the concrete.  The plastic webs are embedded in the EPS for rigidity.  Here is a close up of the block:

 

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Note the teeth on the top and bottom edges of the EPS, these ensure the blocks securely interlock with each other.  The markings on the side of the blocks are to aid cutting and are set at 20mm intervals.

So, after measuring and setting out, the first course of ICF blocks were laid. These were half blocks, a full block having been cut in two with a table saw so that there was a flat edge to sit on the concrete strips. A second full course followed, taking us up to just above finished floor level.

 

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The pour to fill the hollow core of the blocks took 1 hour.  C35 concrete had waterproofer and steel fibres for strengthening added to the mixer. You can see the steel fibres here:

 

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A hoistable skip was filled by the concrete mixer and lifted by crane.  Again, a team of four worked their way round the foundation, releasing concrete from the skip into a ‘funnel’ which ran on metal rails fitted over the top of the ICF blocks.  The rails allowed them to quickly slide the funnel along the ICF block wall, filling up the core as they went.  2 men worked the skip and funnel, while a third, following immediately behind, used a vibrating poker in the core to agitate the mix and encourage settlement.  Every segment of the block (as separated by the plastic webs) had the poker treatment.

 

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My builder followed round, running a line the length of each wall, bracing it where required to ensure the finished wall was straight and true.

 

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The finishing touch was floating the surface of the concrete in the core to a smooth finish, to aid the painting on of a radon barrier.

 

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 Next entry - Upfill, insulation UFH and slab

 

 

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ProDave

Two comments:

Those are the shallowest strip foundations I have ever seen anywhere. Here we were down to between 1 and 1.6 metres below original ground before we hit the firm sandy clay, and where I used to live in Oxfordshire, the standard was a very minimum of 1 metre deep.

Secondly, whenever I have seen ICF pours (mostly on Grand designs) they pour a whole floor worth of blocks on one go, then wonder why they get bursts. Pouring just a few at a time seems a better idea.

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Guest Alphonsox

Guest Alphonsox

Posted

Looking very clean and tidy too - You'll be in danger of giving the building trade a good name.

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Stones

Stones 1037

Posted (edited)

 

On 5/31/2016 at 18:02, ProDave said:

Two comments:

Those are the shallowest strip foundations I have ever seen anywhere. Here we were down to between 1 and 1.6 metres below original ground before we hit the firm sandy clay, and where I used to live in Oxfordshire, the standard was a very minimum of 1 metre deep.

Secondly, whenever I have seen ICF pours (mostly on Grand designs) they pour a whole floor worth of blocks on one go, then wonder why they get bursts. Pouring just a few at a time seems a better idea.

The site only had 200mm cover of topsoil, and in digging into the hillside we were well into the hard so no need to go any deeper.  Standard 150 x 600mm concrete strips, which despite the deceptive photos, are 450mm below finished ground level.

The next pour as I understand it will be to wall plate, so 6 blocks high.  I'll  know more when the actually do it, but there are a stack of adjustable braces sitting on site ready for that stage. I think the key thing is getting the foundation courses in so there is a solid and fixed base from which to build the main blocks off.  The bracing will be fixed prior to the pour, then adjusted to straighten out and kinks in the block work.

I suspect that avoiding blowouts is more about taking time and not rushing, than inherent problems with ICF per se. The biggest difference compared to what I have seen on the likes of grand designs, is that without a pumped boom concrete wagon, the process is a lot slower, and doesn't appear to put the blocks under as much stress.  I'll know in a couple of weeks!

 

Edited by Stones
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Stones
14 hours ago, Alphonsox said:

Looking very clean and tidy too - You'll be in danger of giving the building trade a good name.

Yes, it's very refreshing. It's by far the best managed site I've had. 

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