Hi just wondered if anybody had done any costing of a passive slab with ufh, verses the more traditional strip foundation,concrete blocks up to dpc, beam and block,insulation, ufh, screed. 

 

I have not done any figures yet and I know the passive slab components can be expensive to buy, but when you look roughly at all the different elements that are needed to get up to ffl in a standard strip footing I'm leaning very heavily towards an insulated raft. 

Cheers russ. 

In my situation it was coming out much more expensive for the passive slab due to the depth of hardcore (muckaway and hardcore cost) that the structural engineer wanted. We have clay soil so I would say the the exact answer depends a lot on this, and if you can lose the soil onsite.

For us it was the cheapest option, again because of the soil conditions, plus the fact that we had already excavated down over 2m, just to get the site level.  Digging out more for strip foundations would have cost more than just putting the passive slab down.  As @Trw144 rightly says, it does all come down to what the ground conditions are like.