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Concrete or stones around house with clay soil.

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  1. #1
    JB1
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    Default Concrete or stones around house with clay soil.

    Hi,

    The house I'm building is on reactive clay soil. The foundation bordering the house has 450mm x minimum of 2000mm deep piers every 1.5m.

    I think the whole house has been well over engineered from the footings to the steel beams (every tradie who has seen the plans has been surprised how over engineered it is). I'm not complaining too much as IMO it's better than under-engineering it.

    I like the look of stones with concrete pavers around the house and I will install agri drain so water doesn't pool or stagnant around the house.

    I'm wondering due to my soil type and to protect the house, are stones walkway around the house a bad idea?

    Or is it a much better idea to concrete a 1m border along the house?

  2. #2
    3K Club Member johnc's Avatar
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    Quote Originally Posted by JB1 View Post
    Hi,

    The house I'm building is on reactive clay soil. The foundation bordering the house has 450mm x minimum of 2000mm deep piers every 1.5m.

    I think the whole house has been well over engineered from the footings to the steel beams (every tradie who has seen the plans has been surprised how over engineered it is). I'm not complaining too much as IMO it's better than under-engineering it.

    I like the look of stones with concrete pavers around the house and I will install agri drain so water doesn't pool or stagnant around the house.

    I'm wondering due to my soil type and to protect the house, are stones walkway around the house a bad idea?

    Or is it a much better idea to concrete a 1m border along the house?
    Once of the biggest problems with clay soils is their saturation and later drying out which cause the movement. Stones provide a mulching layer that reduces drying and allows moisture to pass through. Depending on the situation they should retard evaporation loss and minimise excessive drying. If anything stones should give a more stable outcome, I'm not sure I would be to keen on concrete all round as this most likely will reduce recharging of the clay during winter however i'm sure others will have a view.

  3. #3
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    Read through your "Construction Footing Report" you got from your structural engineer. It may indicate what is required. Both of the houses I built were built on clay and in both cases it was a requirement to provide an impermeable border 900mm wide around the footing. Failure to do so would invalidate the design of the footing. Maybe just Adelaide soils?
    Good enough today is better than perfect tomorrow

  4. #4
    JB1
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    Thanks for a replies.

    A lot of think about.

    Johning- Footing/Engineering design does not mention any impermeable border that is required.

    I'll chase up the engineer who designed my house, but he's on leave at the moment.

    It would be nice not to be have concrete all the way around the perimeter- from an aesthetic view.

  5. #5
    Golden Member manofaus's Avatar
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    I have a similar block and part of my initial foundation construction was to actually build up a pad of crusher dust that was 300mm thick and then put the slab on that with piers through this pad and into the clay. The pad was to extend past the house footprint 1500mm. Seeing as the slab was going to be a waffle pod slab, I had 400mm to play with. He said it would be no drama then to have a potted garden around the house using pebbles or stones.
    sorry for the ramble.

  6. #6
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    I'm going through a similar situation at the moment. I found tree roots under the house while restumping and worms in the dirt under the verandah. I thought of all sorts of ways to combat the mousture under the house ( the house did have a drain arround it but only about 100mm deep). The builder who is undertaking the work I can't do was/ is adamant, if I didn't want mousture under my house I needed a concrete barrier and in my case it's got to be dug down to rotton rock which is about 500 to 600mm deep on average. The cost will be approx. $1600- and from a resale point of view worth every cent.

  7. #7
    JB1
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    Default Concrete or stones around house with clay soil.

    Rock is approx 2500mm deep.

    I spoke to my engineer.

    He said it doesn't need concrete as long as the natural ground level is more than 150mm below the slab.

    It's ~150mm now, but by the time I dig the ground for an agi drain (and cover with stone) the clay will be at least 300mm lower.

    But note that I have deep piers surrounding my house.


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