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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorgyrogear
    • CommentTimeFeb 2nd 2018 edited
    I need a bit of extra height in my crawlspace, for a solar storage tank, and this implies exposing a strip footing, over L = 7 foot or so.

    The blocks are 200mm and the wing is generally 250mm, locally wider.
    Footing appears to be around 6 inches thick, and sitting on solid bedrock (mudstone).
    I'd also like to trim the wing to 250mm (using a cutting wheel) (as depicted by the rebar).

    (see photo).

    Per F. CHING, the triangle of forces starts at the bottom corner of the footing, and extends outward at a slope. However I do not intend going below the bottom corner of the footing in any case.

    Would then recast the footing with high-strength concrete, inside a form board.

    Just thought I'd seek comments before going past the point of no return... :shamed:

      stripping the footing.jpg
    • CommentAuthortony
    • CommentTimeFeb 3rd 2018
    You may trim the overspill but under no circumstances go below the bottom of the footing unless you are underpinning it

    The wing overspill was potentially helping the footing but it will be OK without it, don’t ask and engineer and please don’t sue me for this practical down to earth opinion.

    It seems to me that you have dug below the footing and already encroached into the 45degree zone though could you draw a section through existing and proposed please and post them
    • CommentAuthorgyrogear
    • CommentTimeFeb 3rd 2018 edited
    Many thanks Tony, as usual !

    No, I won't sue you, except for the five quid I paid to get on here ! :devil:

    Enclosed is situation drawings.

    I "heavily explored" below the wing overspill: the concrete is 160mm thick and there is 40mm that I scraped out with my hammer, then it is solid rock - my usual heavily consolidated shale... It does not so much "ring" to the hammer, as give a dull boxy thudding noise...

    I was trying to avoid underpinning this wall for OBVIOUS reasons !

    (I already underpinned the entire north and E &W (gable) walls (= 20m run) when installing edge insulation to my (still-in-progress...) limecrete slab, just don't anybody tell my O/H...


    Thanks again,

    • CommentAuthortony
    • CommentTimeFeb 3rd 2018
    That will be fine, I am more worried about the rough rubble wall the other side, needs to be 200mm thick for the bottom 600mm
    • CommentAuthorgyrogear
    • CommentTimeFeb 3rd 2018
    Thanks a lot, Tony, you are saving my bacon !

    I did *build* the rough rubble wall 200 thick (that is why the trench is only 1000 wide, as opposed to 1200 before).
    The coping/parapet wall is 150 thick and 170 high.

    Enclosed is photo of general layout showing RR wall and slab, and crosswall footing.
    Free height above slab is only 800 so no heavy machine tools in that bit LOL

    Profuse thanks again of your technical opinion.

      crawlspace general view.jpg
    • CommentAuthortony
    • CommentTimeFeb 3rd 2018
    All looks good

    Are you a hobbit by any chance?
    • CommentAuthorgyrogear
    • CommentTimeFeb 3rd 2018
    I'm not really in the hobbit of saying, but YES !

    (certainly no Troll, me !):devil:

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