Passive slab

[eandg]

Looking for a bit of info on passive slab foundations - how much of a premium do they come in at compared to a normal raft? Any issues/concerns/recommended suppliers (in Scotland)?

[LA3222]

I had quotes of £24k to £34k to supply & install a 170m2 insulated raft.

 

When I obtained quotes for supply only of the insulation, they all came in at around £9k.

[Jeremy Harris]

We had quotes that, when adjusted to the same spec (a couple didn't include labour, one didn't include steel reinforcement, two didn't include the concrete), came out at around £10k to £13k, for a 85m² slab, including UFH pipes, so about £140/m².  This was over 5 years ago now though, so I'd expect the prices to have risen a bit and I'd think around £150 to £180 per m² would be closer to current prices. 

[LA3222]

My quotes have come in within the last couple of weeks, one of which was part of a slab/frame package so my prices of £140 - £190 per m2 are very up to date. 

 

With UFH pipes installed I am looking at £205 per m2.

Edited February 7, 2019 by LA3222

[Oz07]

2 hours ago, JSHarris said:

We had quotes that, when adjusted to the same spec (a couple didn't include labour, one didn't include steel reinforcement, two didn't include the concrete), came out at around £10k to £13k, for a 85m² slab, including UFH pipes, so about £140/m².  This was over 5 years ago now though, so I'd expect the prices to have risen a bit and I'd think around £150 to £180 per m² would be closer to current prices. 

I remember the posts as it was happening like yesterday. Bloody 5 years ago. Costs don't seem to have changed much if 170m2 quote is recent. 

 

Bear in mind op that there will be many site specific variables coming out of ground

[epsilonGreedy]

3 hours ago, JSHarris said:

We had quotes that, when adjusted to the same spec (a couple didn't include labour, one didn't include steel reinforcement, two didn't include the concrete), came out at around £10k to £13k, for a 85m² slab, including UFH pipes, so about £140/m²...

 

 

I imagine the figures exclude the cost of excavation into the gradient of your site as this was site specific? What about the laying down of hardcore to create a stable plinth for the insulation build up, was this work included in the quote?

 

I ask because I am just trying to assess the overall cost compared to traditional footings.

[LA3222]

The quotes I had include laying the hard-core layer to a depth of 150mm.  If your ground conditions require more then that is additional cost.

 

The assumption is also a flat and level site excavated to the required depth at your own cost.

 

They will then lay drainage pipes etc in the slab to the correct position, but they terminate 1m beyond the slab perimeter.  Any further work is your to do.

[LA3222]

I'm currently working out the cost of strip foundations with a ground bearing slab to get a feel for cost difference.  At the minute I'm at a figure of £20k for strip (excl labour) so 16-40% cheaper but Labour is not accounted for.

[Jeremy Harris]

47 minutes ago, epsilonGreedy said:

 

I imagine the figures exclude the cost of excavation into the gradient of your site as this was site specific? What about the laying down of hardcore to create a stable plinth for the insulation build up, was this work included in the quote?

 

I ask because I am just trying to assess the overall cost compared to traditional footings.

 

The site levelling was a part of the ground works contract, as we needed to excavate down to about 2.5m below the highest point to get the site level.  The ground works contract also included laying the 150mm sub-base of MOT 3, although this wasn't that costly as it was a part of a very much bigger job.  Looking at the QS breakdown, the sub-base for the passive slab cost just over £1k.

[eandg]

1 hour ago, LA3222 said:

The quotes I had include laying the hard-core layer to a depth of 150mm.  If your ground conditions require more then that is additional cost.

 

The assumption is also a flat and level site excavated to the required depth at your own cost.

 

They will then lay drainage pipes etc in the slab to the correct position, but they terminate 1m beyond the slab perimeter.  Any further work is your to do.

Are your quotes from national providers and are the same companies laying ufh and the slab?

 

I have a groundworker friend who we intended on using for all excavation and to lay strip foundations but it now appears that a raft will be required and if so, we'd be happier paying a bit of a premium for a passive slab in which case we will procure from elsewhere and use him to get the plot slab-ready. Is there any DIY options that an experienced groundworker could do themselves?

[LA3222]

I have had quotes from Kore, AFT and build lite.  Funnily enough they are all very similar in price for supply only of the insulation - around £9k delivered for approx 170m2.

 

One of them gave a supply and install quote of about £24k whilst the other supply and install quote was with a TF company who do the frame also which came in at £34k for the slab.

 

Both of the supply/install included all components and ancils.  It also included supply and lay of 150mm hard-core for the sub base.

 

Anything outside of this is yours to sort out so if your ground conditions aren't favourable more excavation/hard-core may be necessary at your cost.

 

UFH would be an extra £2k. 

[Gone West]

We had a 90m2 Isoquick PH slab supplied and installed and it was £18538. This included 250mm compacted type1 and 50mm granite fines laid extending 700mm beyond the perimeter of the insulation. The insulation was 300mm thick and the concrete 200mm thick. This was installed onto a level site with all services ducting and soil pipes already laid. This was nine years ago and was the first to be installed in England so we probably paid a premium.

[Oz07]

14 hours ago, PeterStarck said:

We had a 90m2 Isoquick PH slab supplied and installed and it was £18538. This included 250mm compacted type1 and 50mm granite fines laid extending 700mm beyond the perimeter of the insulation. The insulation was 300mm thick and the concrete 200mm thick. This was installed onto a level site with all services ducting and soil pipes already laid. This was nine years ago and was the first to be installed in England so we probably paid a premium.

Got a 2 for 1 offer on slab didn't you?!