Passive slab help

[RichS]

Hi all, new kid on the block here, seeking advice from those who know

 

Hopefully I will shortly be receiving my planning permission, fingers crossed!. It's taken me 18 months+ to get to this stage and numerous changes to the drawings. However I am quite happy with what we have ended up with. So this is likely to be the first of many questions.

 

 I will be doing the majority of the works myself and had anticipated building off traditional type foundations. However I know the ground is not good and accordingly I thought I may end up with a reinforced ground beam and worse case scenario that to be sat on piles. Then I start reading more and more about passive slabs. I can see a number of advantages to this system, not least being the vastly reduced amount of spoil to be removed from site, and the cost saving involved. So the question I would like an answer to is "Is a passive slab suitable for soft ground conditions". Everything I have read so far seems to indicate that they are, subject to SE confirmation.

Can anyone confirm (or refute) this??

The second part of the question, my footprint is approx. 128m sq, 45m sq of this is garage. What happens with the garage area??. I would imagine that you simply increase the thickness of the slab in that area, i.e. 100mm for house, 200mm for garage, all plus steel of course. Is that assumption correct?.

 

I should add that I intend to build using ICF, I haven't yet determined who's system it will be, still trying to work out all the pro's and cons.

 

Thanks

 

 

[jack]

Morning and welcome.

 

I understand that the passive slab approach works very well on soft ground.  Indeed, when our (private) building inspector's engineer demanded a statement from us about why we chose this rather than more conventional foundations, MBC's (supplier of slab and timber frame) engineer pointed to the relatively low bearing pressure of the ground we're building on.

 

We have an attached garage.  There's a separate EPS upstand between the garage and the house so that the slabs are effectively thermally insulated from each other.  The garage slab is still only 100mm thick on 300mm EPS, although there's a full width 100mm deep reinforcing rib every 1200mm or so from memory.  

 

One thing you do need to think about is the transition from outside to the slab (See here: http://forum.buildhub.org.uk/ipb/topic/416-handling-transition-into-garage-on-raft-foundation/).  

 

Feel free to drop me a pm if you'd like me to email you our passive slab plans.

 

[joe90]

I was going passive slab and do believe they are a very good idea especially for soft ground, however you will need an SE to sign it off as far as my building control was concerned.

[mvincentd]

Hi

Good luck with your build.

I'm also intending to use ICF and just last week went on the 1 day training course for Nudura.  I'm thinking most of the ICF's will 'do the job' but it's worth a premium for the ease of working with Nudura's more 'evolved' product.  Would be interested in your conclusions.

Sounds like you're getting into the details with the garage issue so you might want to choose an ICF soon because detail drawings done to brick dim's could be a pain depending on which ICF.

[jamiehamy]

There are few limitations in terms of block size when using Polarwall,apart from course height.  Might not matter for a standard build as much but certainly simplifies build and icf spec as there us no need for special pieces on corners,  arches,  lintels etc... 

[Fallingditch]

+1 for an insulated reinforced concrete slab. We are on London clay in flood zone 3a. The slab option was so much less intrusive than piles. PM me and I'll let you know what we spent.