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Green Building Bible, Fourth Edition
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    • CommentAuthormarsaday
    • CommentTimeJul 29th 2017
     
    I have just dug out the foundations today pretty much fully. I am a little deeper than required by BC, but i am a little out on levels. Some areas are a little deeper than others.

    Can i use sharp sand to fill in the bottom of the trench to make a really nice level ? Or do i just leave it as it is let the concrete take up any imperfections. I am talking about 30mm too much soil removed in some places.
    • CommentAuthorDandJ
    • CommentTimeJul 29th 2017
     
    Leave as is. BC will want to see the bottom of the trench not something else filled in over it. Also too deep will not be a problem as far as BC is concerned, but if the whole job looks tidy and gives the impression you know what you are doing it can help. (Comments come from 20 years in construction, the last 10 or so mainly for groundwork companies involved in digging foundations.)
    • CommentAuthormarsaday
    • CommentTimeJul 29th 2017
     
    Ok, yes i don't want to hide any problems, but after it has been ok'ed do people use a little sharp sand to get a nice level or is it just straight in with the concrete ?
    • CommentAuthortony
    • CommentTimeJul 29th 2017
     
    ONLY concrete
    • CommentAuthorCWatters
    • CommentTimeJul 30th 2017
     
    I'm quite impressed you are only 30mm out. Hope the rain holds off for you.
    • CommentAuthormarsaday
    • CommentTimeJul 30th 2017
     
    Well probably more to be honest. I am doing a little more digging tomorrow to get a better level and then i need to fix some steel rods in the stone henge foundations i have already in place which used to be for the conservatory. The BC guy said i could leave them in and add new foundation to it.

    Can someone clear up something for me though on doing foundations. Is it ok to have a strip foundation which is a bit deeper in sections because of a not so straight forward digging out process?

    The general box shape will be pretty level give or take 30mm, but i have a section where a sewer has had to be exposed and i must lay concrete under this and then box it off, so the new foundation will stop just around it. I will then bridge with lintels. However, my trench slopes down towards this sewer as i had to work down there and ended up digging out a larger hole.

    know i can create a step, but to be honest i just thought using more concrete would be easier to do. So i will have a section of foundation where the depth will start out at 250mm deep and become maybe 400mm deep nearer to the sewer. Does this deeper depth cause a problem ?

    This photo shows my drain and the conservatory foundation.
      IMG_0535.jpg
    • CommentAuthorMike1
    • CommentTimeJul 30th 2017
     
    The extra depth is unlikely to be a problem, but if you run it past your BCO when they inspect the trench they'll be sure to tell you if they have any concerns.
    • CommentAuthortony
    • CommentTimeJul 30th 2017
     
    I have concerns! The horizontal sharp bend needs to be a rest bend and to be accessible

    I would have gone straight from that bend down into the drain run with only one more slow bend, a very long radius pipe cut for the purpose.

    Plastic drained don't block easily but that one will.

    Will the exposed foundation be underpinned?
    • CommentAuthormarsaday
    • CommentTimeJul 30th 2017
     
    That exposed foundation is the old conservatory foundation and my new foundation has to go under it and then fill the trench next to the length of redirected drain pipe. So yes it is going to have new concrete in place.

    This drain set up is a strange one and i posted about it before. It is taking a single overflow outlet for my neighbours conservatory roof and was built years ago to sweep into my garden and connect up with the main foul drain running on into the neighbours garden. So it is carrying rainwater only, not waste.

    All this pipe work was in my trench for the new foundations, but now it is set up crossing the foundation in one place only. The section next to the back wall of the house will be coming through the new wall of the extension and so will be bridged in the wall. The length of pipe running next to the new foundation trench will be sat under my new timber floor. So it is potentially accessible. The connection into the sewer run (which you can see in this other photo) is to be bridged and then covered in gravel etc. I wonder if it is an idea to actually create a proper brick manhole around this for future access. It would mean creating a type of trap door in the new suspended timber floor.

    BC will be out tuesday so i think all will be ok.

    PS the gully is a rodable type.
      IMG_0533.jpg
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