Insulated raft foundation

Bobbiblu

Hi All,

I'm just wondering if anyone can point me in the right direction for an insulated raft foundation. I've been googling it but haven't come up with anyone who'll just do an insulated raft without trying to flog me a full house. Am I missing something??? I'm still awaiting quotes from insulation firms (all the usual suspects) but I'm not sure they'll incorporate this...would they? sorry if these are really basic questions but I've still only got my L plates as far as this construction business is concerned. Many thanks in advance.

BB

Native Hawk

Where are you from? Should be no problem to get somebody to do the raft only!

Bobbiblu

In south Co Carlow.. its the insulated part that's the issue I think or am I over complicating it?

Native Hawk

What kind of insulation is it? Is the insulation been placed below or above the raft?

sas

Seeing as you are also interested in ICF I assume you are talking about the insulation under the concrete raft.

PM sent.

Bobbiblu

sas wrote: »

Seeing as you are also interested in ICF I assume you are talking about the insulation under the concrete raft.

PM sent.

Yes, that's exactly what I'm looking for. Many thanks sas

big neilly

sas wrote: »

Seeing as you are also interested in ICF I assume you are talking about the insulation under the concrete raft.

PM sent.

i have been searching web for a lifetime trying to find info on insulated raft foundations to work along with icf construction

YourAverageJoe

************ System?


read the charter

syd

is maith liom chocolate

am thinking of building a sun room to back of house with a raft foundation , so far got a couple of quotations and they seem to be over the top especially as its not a hugh build

BryanF

did you give them a spec & drawing or did you ask them to 'make-up' what they are meant to do for you?

is maith liom chocolate

I gave them a specific drawing.

liamolaighin

I'm in Cork and I'm also looking at an insulated foundation. Want to eliminate cold bridges as much as possible as I'm going with underfloor on both floors. Itt's been indicated to me that I can get the insulated foundation for approx same price as normal strip foundation. I have 1 quote back and its €23,000 for the 3000 sq/ft house. No underfloor or plumbing included in quote. Thats quite a bit more than normal strip foundation but i'm waiting on another quote also.

Also want to eliminate cold bridges around window and door openings and external insulation is being recommended to me to achieve best insulation and eliminate cold bridges. I was planning a 200mm pumped cavity, with internal insulated dry-lining and again it's been indicated to me that I could do the external insulation applied to a single leaf of block on the flat for approx the same price as my 200mm cavity but with much better results.

These are the 2 areas of my house I'm uneasy about at the moment. I can have local tradesmen build direct labour and it would be quite straightforward. Going the other route would be a more complicated build for local contractors.

I'd appreciate any advice/expertise from people out there. Is it worth the extra money in the long run. Want to build a low energy house, but cant afford to go completely passive. Will have MHRV system and possibly geothermal heatpump. Triple glazed good quality windows (0.8 u-value)With good building standards house would be very cheap to heat. Going back to my energy assesor soon to review spec of house, just need to decide how to get the best value for my money.

about2build

If you're going low energy you wont need the geothermal and with the cost of those things id scrap it and put the money into the fabric.....im going 250 mm pumped cavity and think it is the best way to achieve a low u-value in a masonry build.....details around opes should be dealt with by your arch and yes i understand th eprob with the cold bridge at bottom floor connecting to slab.....any ideas on that out there??

BryanF

about2build wrote: »

th eprob with the cold bridge at bottom floor connecting to slab.....any ideas on that out there??

yes

adrianegan3

Has anyone put in the insulated raft System and what is their views on it is it worth the expense

BryanF

Yes, subject to 1:5 detailed drawings being prepared of all major junctions, so the guys laying out the EPS system understand what going on.

Metric Tensor

It needs a careful and specialist structural design too! The structure needs to be confirmed to the millimetre in advance of construction. (Of course this should always be the case - but sometimes isn't!)

adrianegan3

Metric Tensor wrote: »

It needs a careful and specialist structural design too! The structure needs to be confirmed to the millimetre in advance of construction. (Of course this should always be the case - but sometimes isn't!)

Agreed how do they compare on strength to a traditional Raft they claim they need less Concrete are they likely to move with settlement

Metric Tensor

That's an awkward question because foundations are a balance of the two items below:

1. The best engineered foundation is the cheapest, smallest foundation that can satisfactorily hold up the building throughout its design life including worst case scenarios.
2. If there is a flaw in the foundation it is almost impossible to fix completely and any partial fix to the faulty foundation or the items it affects will be hugely expensive.

So ... you can't really compare the "strength" of foundations because they do the same job differently and in different circumstances.


In terms of settlement - three items can contribute:

1. The prepared ground beneath the structural footing (which should be considered part of the "foundation")
2a. The reinforced concrete in the footing/slab/raft - i.e. its design and its installation.
2b. The long term dimensional stability of the insulating material.


Items 1 and 2a are common to most "shallow" foundations in Ireland and 2b is the unique or semi-unique item in the passive raft.