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sub floor ventilation

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  1. #1
    Apprentice (new member)
    Join Date
    Apr 2004
    Perth W.A.

    Smile sub floor ventilation

    Hi , We have just bought a little cottage - limestone foundations , wood floors, but No SFV . House is on a slope , 2 foot of foundation is visible at the front , nil at the back - any suggestions on how to knock in some SFV through crumbly limestone ?

  2. #2
    Pretend my avatar moves! bitingmidge's Avatar
    Join Date
    Nov 2003
    "The Home of the Biting Midge" MountainCreek Qld


    Two thoughts!

    1) Get a concrete drilling and sawing company in to core drill some holes using their machinery. The limestone will be a bit like going through butter with a hot knife for them and the cost should not be too great. Drilling will mean that there is less impact on the "crumbly" limestone and you will have much cleaner holes. Trim around the outside by hand to square 'em up, and size to suit whatever grille you choose.

    2) Leave the limestone alone, and cut (say 150 x 100) openings straight through the floor every two or three metres around the perimeter of the building. Cut the holes to suit the standard subfloor heating grilles that are available in places where it's cold enough to build houses out of limestone! Don't use this method if the subfloor already has some ventilation, as you will certainly get drafts that you don't currently enjoy!

    Make sure that whatever method you choose that you locate vents in opposite sides of the building so that it does cross-ventilate.

    good luck


  3. #3
    Join Date
    Aug 2003


    I thionk if you use method 2, you'll regrete it for the smell that if will bring into your house.

    Cheers, Pongy

  4. #4
    1K Club Member journeyman Mick's Avatar
    Join Date
    May 2003
    Kuranda, paradise, North Qld


    Plus method 2 is not legal (in Qld in any case) I can't remember exactly how it was worded, but basically smell and vermin are a problem. If you had to you could use method 2 but then build a duct over it that vented out through the wall.


  5. #5
    Pretend my avatar moves! bitingmidge's Avatar
    Join Date
    Nov 2003
    "The Home of the Biting Midge" MountainCreek Qld

    Default Aaaazrgh!

    Ozwinner & Mick,

    Where would I be without you guys? For the second time in recent history a case of brain fade, I'm afraid......

    6.45 am is clearly far too early for me!

    With regards to method 2

    It's not my preferred but appears to work: (and this is the bit that I simply left out so the world would cut holes in their floors and blame me later!)- but there needs to be an exhaust system in place.

    I'll explain:

    This method is apparently often used in commercial buildings or cottages where there it is not possible to provide ventilation access to the outside perimeter, and requires a flue to be constructed from the sub-floor space, (or the apparently the use of an existing dis-used fireplace) to vent to the outside.

    If an existing chimney is used it may "draw" sufficient air on it's own account, but other solutions I have seen seem to work quite well with a 100 or 150 diameter (4" or 6") vent pipe with a small inline fan.

    The theory is that the perimeter floor vents will allow relatively dry air down to the subfloor space, to be drawn out in centre of the building by the exhaust system, if all is working the air-flow should keep smells at bay!

    I used it effectively in a CBD basement a few years (decades!) ago, admittedly with a big sucker of a fan exhausting throught the footpath.

    I also saw a version of this system working in Ireland (should that have set little bells ringing?)a couple of years ago, admittedly in an old pub, where you couldn't tell where the bad smells were emanating from!

    There was an open coal fueled fire place and the vent flue connected into the brick chimney and used convection to draw the air from the subfloor. I don't know what impact that all had on the overall heating of the room, but since hot air rises, I am assuming that the draft was minimal, and the loss of cooler air at the floor level was acceptable.

    I am not sure about the illegality Mick, don't see why it couldn't be done with vermin mesh? I have heard that floor wastes with frog-flaps are illegal too, but haven't been able to confirm.....maybe a plumbers conspiracy at work?

    Anyway, my apology for the half-baked response initially, it's not my favourite method anyway!



  6. #6
    2K Club Member seriph1's Avatar
    Join Date
    Jan 2004
    Kilmore, near Melbourne, Australia


    would LOVE to see pics of the house

    couldnt you remove some mortar or some entire blocks - CARFEULLY and approriately(ie: steel bar across opening - and replace them with mesh vents painted a complimentary colour?
    Kilmore (Melbourne-ish)

    ....catchy phrase here

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