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  1. #1
    Join Date
    Aug 2007
    Location
    Sunshine Coast
    Posts
    7

    Default Level for Foundations

    I am building on a sloping bush block, using steel piers for the subfloor. But to make best use of the space under this floor, I intend to place a half concrete slab on the lower side (that is, cut into the slope where necessary to create an extra couple of rooms).

    I want to know at what level to excavate, allowing for the concrete slab, and subflloor beams and joists?

    I plan to get an excavator to do the main cut, then a bobcat for tidying up and dig footings, etc. I DO NOT plan to do a "cut and fill" - I have enough space to dispose excess soil, so will cut only.

    My plans show, say, 100mm thick concrete slab (with deeper footings), 200mm beams, 200mm joists and a wall height of 2400mm.

    Does this mean I mark the level of the cut at 2900mm (100 + 200 + 200 + 2400) below the finished floor level?

  2. #2
    Join Date
    Oct 2003
    Location
    Kentucky NSW near Tamworth, Australia
    Age
    86
    Posts
    1,067

    Default

    Chandler

    You wouldn't allow for the the beam depth only to the ground level under your slab. The beams would be below your ground level.

    But you really should be having your plans drawn up first and have an engineer detail for your concrete slab because it will depend on what type of structure you are having as to what size the beams will be. e.g. Brick or timber construction, tile or steel roof etc.

  3. #3
    Join Date
    Aug 2007
    Location
    Sunshine Coast
    Posts
    7

    Default

    Thanks for your reply Bazza, but I am not sure what you are saying.

    The plans have been drawn and approved by a structural engineer, but in regard to levels he just advises the builder to check on the ground.

    I want to avoid excavating too much (or too little) soil for the slab, so want to establish a level for the excavator to cut down to.

    I have included a drawing of the cross-section (level.jpg) which may explain how far below the proposed (first) floor level I should cut the platform for the slab.

    Maybe its not a big deal, because I can alter the height of the piers on the upper slope when I build the steel subfloor.

  4. #4
    Join Date
    Sep 2004
    Location
    Strzelecki Ranges Victoria
    Posts
    395

    Default

    As I read it your joists are 200mm
    The beams [bearers] supporting the joists are 200
    from the underside of the beam to the top of the slab is 2400
    if this is correct - from underside floor level to excavation is 2900 plus 50mm for packing sand under the slab.
    Peter Clarkson

    www.ausdesign.com.au

    This information is intended to provide general information only.
    It does not purport to be a comprehensive advice.

  5. #5
    Join Date
    Aug 2005
    Location
    Victoria
    Posts
    412

    Default

    If you are lining the ceiling below you need to consider the battens and lining as well.

    Tools

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