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Passive slab installation time lapse


Alex C

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I have put a time lapse of the whole passive slab installation on my blog http://www.passivehouseselfbuild.co.uk/passive-slab-foundation/

For anyone considering this type of foundation but don't know exactly whats involved it gives a pretty clear indication of how it is done. I have had comments from every other trade on site about the quality of the power floated finish, so well done to the MBC team.

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What you will find, if your experience is similar to mine, is that the accuracy of that slab finish, together with the accuracy and squareness of the frame, will save a significant amount of time (and money) down the line.  In my case it saved around 2 days labour on the flooring, could have saved around 30 sheets of (over-ordered) plasterboard, saved about 1 1/2 days in boarding out time and probably another day in first fix electrical fitting time. 

Had I known about all these small savings (that add up to a significant total saving) then I'd have been less concerned about the initial price.  Like everything in building there are lots of hidden costs and benefits that you often don't find out about until it's too late.

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Our plasterboard tackers were particularly complimentary on the quality of the battening, especially around Velux windows and other tricky areas, definitely saved them time and helped pull in the schedule. 

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Great blog Alex, interesting to see that the green airtightness board is now pre-fitted to the panels in the factory.

I think our build was the first to use them as Joe brought the manufacturer round to see them in situ, ours were fixed after frame erection so it must be saving them a good few days on site.

Nice to see Jack the roofer there as well!

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12 minutes ago, Weegaz said:

Would anyone be able to give an approx cost per m2 for the complete passive slab to include the UFH pipework?

Varies a great deal with the size of the slab, as some of the fixed costs remain the same for larger slabs.

As a guide, we had quotes from three suppliers, Kore, Isoquick and Supergrund, all excluding the UFH pipework (but that only added around £400 to the price for any of them).  The quotes were really hard to compare, as they were all based on supplying different levels of stuff.  None included concrete, one included the steels, for example.

I worked back to get a common standard to compare prices and they ranged from around £9.5k to 11.5k for a slab with an area of 86m².  The biggest price difference was that one of the systems (Isoquick, I think) needed a 200mm thick slab, whereas the others were 100mm thick with ring beam reinforcement around the edges and where there were load-bearing internal walls.

All of the suppliers only quoted initially for the insulation materials and design, one, when pushed, quoted for the steel.  I had to estimate the labour and the cost of concrete (which varies locally as well, and is a significant part of the cost).

In the end our Kore slab took 4 days labour from two guys, from starting with a roughly levelled and compacted layer of clean stone that our ground works guys had left, to a finished power floated slab with UFH pipes installed.

You could very roughly say that it cost around £100 to £140 per m², including the UFH pipe, but that could vary a fair bit for a bigger or smaller slab in an area where labour or concrete (or both) was a different price.

 

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Hi Jeremy, thank you for this,

We have an existing slab in place but this needs removed (banks decision based on lending) so I am thinking we would now be better to look at a passive slab of approx 150m2.

Our builder has priced for strip foundations but I would assume passive would work out on power cost wise with strip foundations once the screeds etc are taken into account

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  • 2 months later...

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