Foundation options for Wide Cavity

just do it

You'll have seen I've some enquires made about this elsewhere but felt a thread dedicated to it may be no bad thing.

So after a few years of reading about the various wall options I'm set on a wide cavity up to 300mm depending on the PHPP when we get to it. The next question is what foundation to put under it?

The common foundation type around here is a strip foundation and my site is suitable for such a foundation. So the options range from traditional strip with a quin lite block in the internal leaf giving a thermal break to a fully fledged PH standard insulated slab.

Really I'm looking at the best value option striking the balance between cost and insulation/ cold bridging detail.

I'm interested in hearing a bit more about the hybrid mentioned elsewhere which is some form of a cross-bred between a traditional strip and an insulated raft foundation supposedly coming in cheaper than a traditional strip foundation.

P.S. I will be discussing this with my architect who is retained for the whole project but want to tease this out a bit more before getting stuck into it with him. We only re-submitted the planning application with a change of house design last Friday so I want to give him another week or two's break before going hell for leather on build make-up and phpp etc.

just do it

I've been looking at an Irish insulated Passive slab option that claims to come in at the same cost as strip foundations! It has nordic roots at its core, need I say any more?!;) It has Passiv Haus certification but lacks an Agrement certificate. Anyone have experience using such a foundation? How big an issue is the lack of an Agrement certificate?

Needless to say I'd ensure my engineer is happy to stand over it.

BarneyMc

Looking into this myself and yes it seems like both strip (with insulated block) and raft foundations come in at a similar price. Instinct would tell me the strip foundations are better but perhaps only marginally. Anyone with any advice out there??

sydthebeat

lads, youre sailing close to the wind here with two forum rules

1. dont discuss particular products

2. dont discuss structural elements

im willing to let this thread meander a bit but please be careful to ensure no rules are broken.

Any one with anything to say about the particular product can pm the OP if youve anything to say outside of its cost and specification.

just do it

Yes syd, should have said PM's only.

Hard to get some feedback with out giving some hints though. It's tricky trying to strike the balance;).

sydthebeat

i appreciate that, but thems the rules. I think anyone who reads your post and is in a position to reply will 'get it' straight away.

fclauson

My standard (all be it a bit wider) foundation was poured TODAY :D:D:D for a 250mm wide cavity - all supervised by my engineer

Happy to share any detail via PM

fealeranger

Could you PM me the detail Please. I'm going at this myself in 2-3 weeks and would like a look at what I'm facing. Cheers .

slowharry

What is your wall tie spec - for a 300mm cavity assuming its regular block masonry inner and outer leaf?

fclauson

for fear of being muffled - speak to your engineer

muffler

fclauson wrote: »

for fear of being muffled - speak to your engineer

Good advice

just do it

fclauson wrote: »

My standard (all be it a bit wider) foundation was poured TODAY :D:D:D for a 250mm wide cavity - all supervised by my engineer

Happy to share any detail via PM

FC

Nice to get it going I'd say, best of luck:). Fancy guessing a date for the house warming?;)

fclauson

just do it wrote: »

FC

Nice to get it going I'd say, best of luck:). Fancy guessing a date for the house warming?;)

The project plan says 1st Oct - but keep that a secret - we are telling every one Christmas