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Building Regulations and Standards: Earthen floor

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  1.  
    • CommentAuthorBigJ
    • CommentTimeAug 21st 2012
     
    Hi all, I've just started a timber frame strawbale extension to my house and had originally specified a cob floor. I took the specification for a limecrete floor- i.e LECA subfloor to provide insulation and to prevent water ingress, with 100mm cob sub floor and 25mm fine cob finish. The building inspector has taken a distinct dislike to the lack of a DPM. I've now had the calcs. done by Ty Mawr for their limecrete floor system, which, as it has building regs approval, will satisfy (probably) my inspector, however it is only for the whole system i.e including the limecrete, which i don't really want. So i was wondering if anyone has any experience of earthen floors/building regs. Even though the finished floor level will be above the outside ground level, having seen how wet the hole i've made is (i had to pump out foundations last weekend- the joys of this so called summer in north cumbria!) i was wondering if it would be ok/better to use a DPM- i know this will stop the floor's breathability but will it CAUSE problems? and if i do so there isn't really any point staying with the LECA, is there any alternative 'green' underfloor insulation?
    I need to build up the ground any way to maintain the floor level throughout the house, so my tentative thoughts at this stage are (working from ground level up):Compacted subsoil;DPM; drainage gravel (to stop any potential build up of moisture against clay and to build upthe floor height); insulation; ; cob layer; finishing layer.
    Any better ideas, thoughts, comments, experiences would be greatly appreciated.
    • CommentAuthortony
    • CommentTimeAug 21st 2012
     
    Thousands of years experience any good?
    • CommentAuthorBigJ
    • CommentTimeAug 21st 2012
     
    Are they all personal experience?
    • CommentAuthortony
    • CommentTimeAug 22nd 2012
     
    for the floors they are
    • CommentAuthorEd Davies
    • CommentTimeAug 22nd 2012
     
    Posted By: BigJdrainage gravel (to stop any potential build up of moisture against clay and to build upthe floor height); insulation;

    Where would that drain to? Or would it just be ventilated somehow?

    Would an alternative approach be to put sufficient drainage around the perimeter to prevent the soil under the extension from being wet? Avoiding a DPM would avoid condensation on the top of the DPM.
    • CommentAuthorfinny
    • CommentTimeAug 22nd 2012
     
    Try Tim Stirrup at Mount pleasant Eco park, Porthtowan cornwall. He installed a rammed earth floor in a workshop unit, building regs happy:bigsmile:
  7.  
    ....how much of an issue is a non 'breathing' floor...? DPMs are quite difficult to install at a later date...

    J

    PS Equally I would have thought that someone with far less scruples than me might suggest you cut a 500mm strip of DPM and tuck it under the edge of the leca, poking out for the BCO to see when he arrives, I of course couldn't possibly suggest that :wink: Either way would echo suggested subsoil drainage under and around edges.
  8.  
    Dear Mr Norton,

    Of course I have not had the idea that you haven't had, but I wasn't thinking of a 400mm strip. Do you think that would work as well as a 500mm strip?
  9.  
    ...if I had had that idea, which I hadn't, I would suggest some tests as too how much was needed to prevent 'tug out'...

    J
    • CommentAuthorBigJ
    • CommentTimeAug 22nd 2012 edited
     
    Dear all, thanks for the responses. Putting aside the suggestions that definately haven't been made (until last resort) i wonder could anyone enlighten me as whether it is possible to install an earthen floor with a DPM or will it inevitably lead to disaster.
    I should say i am intending to install a french drain around the foundations. The folks at TyMawr did suggest installing drainage pipe under the floor as well to ensure that is kept clear. I guess i'm getting nervous as the pool has refilled today (oh glorious summer) to about 8" deep. My idea with the drainage gravel was to have it over the DPM to provide a place for any moisture that does get in (from above) to sit to allow it to hopefully evaporate over time through the floor so that the actual earthen part does not sit in the wet. PLease let me know if you think this is unecessary/stupid. I suppose that, as nobody has come up with an alternative subfloor insulation material, i could have drainage gravel draining to field drains (with the french drain) then the dreaded DPM, then leca (which could act in a way as previously mentioned for the gravel) then the cob? whilst i know that this basically makes the DPM useless, it would please the BCO. Would it work though?

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