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Insulated raft

  • 11-06-2015 8:51pm
    #1
    kboc
    Registered Users, Registered Users 2 Posts: 458 ✭✭


    Building a new house in the next 12months.

    Are the insulated rafts worth the extra pennies?

    Has anybody done a cost analysis?

    Has anybody put one in? good job?

    thanks


Comments

  • #2
    hexosan
    Registered Users, Registered Users 2 Posts: 1,740 ✭✭✭hexosan


    Do you have to go with a raft in the first place. If so I think its definitely worth it and if I had my time back again it's the way I'd go. By the time you pay labour to erect the shutters for the raft, pour it. Then fit floor insulation, pay labour to pour finish floor your not off the cost of the insulated raft to start with.
    My two cents


  • #3
    kboc
    Registered Users, Registered Users 2 Posts: 458 ✭✭kboc


    No, I don't have to go with a raft. My motivation is quality, longevity, time (length of build) will be a factor too, but not at a huge additional cost way above the alternative method.

    I am not convinced about how long the lite blocks will stop the heat loss over the life time of a building.

    There is an obvious cost associated with this, and that is I suppose the nub of my issue. What is the cost of the convenience and superior quality of an insulated raft? is it value for money.

    Strip foundations would need the following (not an exhaustive list)

    stripping area of soil
    digging out of the foundation
    concrete in foundation
    dead block work
    hard core fill
    blinding on top of fill
    Radon barrier
    sub floor concrete
    finished floor cement/concrete at some point in the future of the build

    An insulated raft (I have no experience so I am having an educated guess here)

    stripping area of soil
    4 inch of stone
    blinding/dust
    insulated raft
    concrete (this could be your finished floor for polished concrete or floor covering on top of this)

    Is this too simplified? there appears to be a lot less hassle with the raft foundation, but an obvious higher cost.

    What do ye think?


  • #4
    rampantbunny
    Registered Users, Registered Users 2 Posts: 907 ✭✭✭rampantbunny


    kboc wrote: »
    No, I don't have to go with a raft. My motivation is quality, longevity, time (length of build) will be a factor too, but not at a huge additional cost way above the alternative method.

    I am not convinced about how long the lite blocks will stop the heat loss over the life time of a building.

    There is an obvious cost associated with this, and that is I suppose the nub of my issue. What is the cost of the convenience and superior quality of an insulated raft? is it value for money.

    Strip foundations would need the following (not an exhaustive list)

    stripping area of soil
    digging out of the foundation
    concrete in foundation
    dead block work
    hard core fill
    blinding on top of fill
    Radon barrier
    sub floor concrete
    finished floor cement/concrete at some point in the future of the build

    An insulated raft (I have no experience so I am having an educated guess here)

    stripping area of soil
    4 inch of stone
    blinding/dust
    insulated raft
    concrete (this could be your finished floor for polished concrete or floor covering on top of this)

    Is this too simplified? there appears to be a lot less hassle with the raft foundation, but an obvious higher cost.

    What do ye think?

    No radon barrier for insulated raft?
    The insulated raft I have seen in the flesh needed steel reinforcement too..not as much as the typical raft foundation but as many corners and joints. Under the load bearing walls, there was mesh/rebar ...I don't know if there is a an insulated raft foundation system available that doesn't require steel reinforcement to tie it together.


  • #5
    Superdaddy
    Registered Users, Registered Users 2 Posts: 234 ✭✭Superdaddy


    I went with the passive raft, it requires steel and dpc/ radon barrier, less concrete, uvalue 0.10, no rising walls, clean site, no cold bridging, finished floor with all services in one pour, no regrets. Worked out very cost effective.


  • #6
    kboc
    Registered Users, Registered Users 2 Posts: 458 ✭✭kboc


    Superdaddy wrote: »
    I went with the passive raft, it requires steel and dpc/ radon barrier, less concrete, uvalue 0.10, no rising walls, clean site, no cold bridging, finished floor with all services in one pour, no regrets. Worked out very cost effective.

    who did you use, by pm thanks?


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  • #7
    galwaytt
    Registered Users, Registered Users 2 Posts: 12,822 ✭✭✭✭galwaytt


    kboc wrote: »
    No, I don't have to go with a raft. My motivation is quality, longevity, time (length of build) will be a factor too, but not at a huge additional cost way above the alternative method.

    I am not convinced about how long the lite blocks will stop the heat loss over the life time of a building.

    There is an obvious cost associated with this, and that is I suppose the nub of my issue. What is the cost of the convenience and superior quality of an insulated raft? is it value for money.

    Strip foundations would need the following (not an exhaustive list)

    stripping area of soil
    digging out of the foundation
    concrete in foundation
    dead block work
    hard core fill
    blinding on top of fill
    Radon barrier
    sub floor concrete
    finished floor cement/concrete at some point in the future of the build

    An insulated raft (I have no experience so I am having an educated guess here)

    stripping area of soil
    4 inch of stone
    blinding/dust
    insulated raft
    concrete (this could be your finished floor for polished concrete or floor covering on top of this)

    Is this too simplified? there appears to be a lot less hassle with the raft foundation, but an obvious higher cost.

    What do ye think?

    Don't forget a standard raft, with the insulation and floor screed over. Even simpler and cheaper than an insulated one.

    Ode To The Motorist

    “And my existence, while grotesque and incomprehensible to you, generates funds to the exchequer. You don't want to acknowledge that as truth because, deep down in places you don't talk about at the Green Party, you want me on that road, you need me on that road. We use words like freedom, enjoyment, sport and community. We use these words as the backbone of a life spent instilling those values in our families and loved ones. You use them as a punch line. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the tax revenue and the very freedom to spend it that I provide, and then questions the manner in which I provide it. I would rather you just said "thank you" and went on your way. Otherwise I suggest you pick up a bus pass and get the ********* ********* off the road” 



  • #8
    kboc
    Registered Users, Registered Users 2 Posts: 458 ✭✭kboc


    galwaytt wrote: »
    Don't forget a standard raft, with the insulation and floor screed over. Even simpler and cheaper than an insulated one.

    I would think internal load bearing walls would be an issue, unless, they are speced by an engineer, but then does this not throw up the issue insulated rafts had at the start. they are not main stream, so you need an engineer to stand over it, where as insulated rafts are fairly common now that the engineering stuff comes with the product.

    Maybe I am missing the simplicity of it?


  • #9
    rampantbunny
    Registered Users, Registered Users 2 Posts: 907 ✭✭✭rampantbunny


    galwaytt wrote: »
    Don't forget a standard raft, with the insulation and floor screed over. Even simpler and cheaper than an insulated one.

    Not sure I follow this. Are you saying raft completely covered with insulation, and then build rising walls on top of the insulation? Then pour screed between.


  • #10
    hexosan
    Registered Users, Registered Users 2 Posts: 1,740 ✭✭✭hexosan


    galwaytt wrote: »
    Don't forget a standard raft, with the insulation and floor screed over. Even simpler and cheaper than an insulated one.

    I built this way and I can assure you Theres very little cost saving in the difference between the two methods. I wouldn't even consider a standard raft to be a simpler build.
    Like I said originally if I'd my time back id definitely go the insulated raft route.


  • #11
    galwaytt
    Registered Users, Registered Users 2 Posts: 12,822 ✭✭✭✭galwaytt


    kboc wrote: »
    I would think internal load bearing walls would be an issue, unless, they are speced by an engineer, but then does this not throw up the issue insulated rafts had at the start. they are not main stream, so you need an engineer to stand over it, where as insulated rafts are fairly common now that the engineering stuff comes with the product.

    Maybe I am missing the simplicity of it?

    Internal walls are no more an issue than another foundation - you'll have local thickening to match structural requirements. You need your foundation designed by an SE irrespective of what method you use.
    rampantbunny wrote: »
    Not sure I follow this. Are you saying raft completely covered with insulation, and then build rising walls on top of the insulation? Then pour screed between.

    No, pour the raft as subfloor. Build your walls. Insulate over subfloor, between walls, and put screed over that.

    Ode To The Motorist

    “And my existence, while grotesque and incomprehensible to you, generates funds to the exchequer. You don't want to acknowledge that as truth because, deep down in places you don't talk about at the Green Party, you want me on that road, you need me on that road. We use words like freedom, enjoyment, sport and community. We use these words as the backbone of a life spent instilling those values in our families and loved ones. You use them as a punch line. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the tax revenue and the very freedom to spend it that I provide, and then questions the manner in which I provide it. I would rather you just said "thank you" and went on your way. Otherwise I suggest you pick up a bus pass and get the ********* ********* off the road” 



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  • #12
    rampantbunny
    Registered Users, Registered Users 2 Posts: 907 ✭✭✭rampantbunny


    galwaytt wrote: »
    Internal walls are no more an issue than another foundation - you'll have local thickening to match structural requirements. You need your foundation designed by an SE irrespective of what method you use.



    No, pour the raft as subfloor. Build your walls. Insulate over subfloor, between walls, and put screed over that.

    OK..got it.
    Confused as thought OP was looking for comparisons versus standard concrete foundations from beginning, but I see mention of strip foundation only on re-reading.

    Friend self-installed an insulated raft last year. Not sure who he bought the kit from. One thing he mentioned was finishing height was the same between internal floors and cavity i.e. there is no step down. The ground falls away from his house but he'd liked to have a step in case water did ever lodge.
    I'm sure there are lots of variations on the insulated form work you can get which have a different detail.

    I considered it myself only discounting it because of concern of movement and potential cracks. Probably never happen on solid ground, but..


  • #13
    galwaytt
    Registered Users, Registered Users 2 Posts: 12,822 ✭✭✭✭galwaytt


    hexosan wrote: »
    I built this way and I can assure you Theres very little cost saving in the difference between the two methods. I wouldn't even consider a standard raft to be a simpler build.
    Like I said originally if I'd my time back id definitely go the insulated raft route.

    Well I can only go by client numbers, but I've seen insulated raft carrying a 50% premium over non. That's a lot of money.

    Ode To The Motorist

    “And my existence, while grotesque and incomprehensible to you, generates funds to the exchequer. You don't want to acknowledge that as truth because, deep down in places you don't talk about at the Green Party, you want me on that road, you need me on that road. We use words like freedom, enjoyment, sport and community. We use these words as the backbone of a life spent instilling those values in our families and loved ones. You use them as a punch line. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the tax revenue and the very freedom to spend it that I provide, and then questions the manner in which I provide it. I would rather you just said "thank you" and went on your way. Otherwise I suggest you pick up a bus pass and get the ********* ********* off the road” 



  • #14
    air
    Registered Users, Registered Users 2 Posts: 2,834 ✭✭✭air


    galwaytt wrote: »
    Don't forget a standard raft, with the insulation and floor screed over. Even simpler and cheaper than an insulated one.
    What thermal benefits does this approach offer versus a strip foundation?


  • #15
    galwaytt
    Registered Users, Registered Users 2 Posts: 12,822 ✭✭✭✭galwaytt


    air wrote: »
    What thermal benefits does this approach offer versus a strip foundation?

    Doesn't necessarily make any difference - that's down to the detail of finishing. The reason for building a standard raft over strip are down to issues of structure, price and speed of build. They will both meet the same structural requirement, but you may be driven to use one over the other say, based on your local ground conditions. (As an example, we find in the UK that the prevalence of tree roots favours deep trench foundations, or soft ground favours piles, or block & beam. They all deliver the appropriate technical 'support' required for the building, but are chosen for some overriding local condition)

    Same here. In the West a strip foundations is rare to see: in Leinster and Munster it's probably the other way round. In N.I. block & beam reins supreme ( :rolleyes: ).

    Either way, all will be detailed thermally to meet Regs.

    Ode To The Motorist

    “And my existence, while grotesque and incomprehensible to you, generates funds to the exchequer. You don't want to acknowledge that as truth because, deep down in places you don't talk about at the Green Party, you want me on that road, you need me on that road. We use words like freedom, enjoyment, sport and community. We use these words as the backbone of a life spent instilling those values in our families and loved ones. You use them as a punch line. I have neither the time nor the inclination to explain myself to a man who rises and sleeps under the tax revenue and the very freedom to spend it that I provide, and then questions the manner in which I provide it. I would rather you just said "thank you" and went on your way. Otherwise I suggest you pick up a bus pass and get the ********* ********* off the road” 



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