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    • CommentAuthordickster
    • CommentTimeNov 29th 2007
     
    So, let's get this straight....even books on straw bale building start you off with "let's pour tons of concrete into the earth"???!

    I'm hoping to build a very modest 80 sq m super insulated bungalow out of Masonite I beam panels. My architect, patient man, starts to baulk at screw in piles (Screwfast) with a timber ring beam and wooden floors. It seems an obvious way to do things without using concrete, but old habits die hard, if at all.

    Has anyone had experience of using this method, what is it that I am suggesting that is so naughty?
    • CommentAuthorbiffvernon
    • CommentTimeNov 29th 2007
     
    Barbara Jones, in her book 'Building with Straw Bales' considers concrete foundations but shows why the disadvantages outweigh the advantages.
  1.  
    We use power driven timber piles, just keep bashing them until the correct resistance is reached. Trim the tops, span bearers then joists and you have a floor to build off (light weight timber construction). A few bolts & braces you have an earthquake proof foundation with no concrete.
    • CommentAuthordickster
    • CommentTimeNov 30th 2007
     
    Thanks for your comments, I considered wooden piles, but this is a bridge too far for the powers that be.
    •  
      CommentAuthorfostertom
    • CommentTimeNov 30th 2007
     
    Fencing contractors sink a 250x250 oak gatepost 1.5m deep in half an hour - how do they do it and why don't they offer cheap pile founds as a sideline?
    • CommentAuthorevan
    • CommentTimeApr 19th 2010
     
    Sorry to dig up a very old thread but there doesn't seem to be much discussion about foundations recently...

    What are possible approaches for a "reduced concrete" foundation? I was hoping that a wider-than-normal trench filled with rubble from the old walls that are being demolished, with a few inches of concrete or limecrete on top?

    Bit naive?

    The walls are probably timber frame with Hemcrete by the way.
    • CommentAuthortony
    • CommentTimeApr 19th 2010
     
    Ram it in there and build away -- will be OK but unlikely to get it past building regs or most engineers.
    • CommentAuthorevan
    • CommentTimeApr 19th 2010 edited
     
    Yeah, I'm beginning to sense a bit of a theme...

    It has to get past building regs or presumably I go to jail.

    Concrete with whatever big lumps of rock I can chuck in when they aren't looking then eh ;)
    • CommentAuthorowlman
    • CommentTimeApr 20th 2010
     
    There are hundreds of thousands of old buildings around, built on dry coursed bricks laid in a clean bottomed trench. only using lime mortar after about 5 or 6 courses. I demolished one awhile ago for the clamp bricks it had stood OK for 180 years, but had suffered from all sorts of modern brick infill, the foundations were in great condition though. The adjacent ones are still standing and occupied. I wonder how all the love of concrete foundations came about.
    •  
      CommentAuthorSteamyTea
    • CommentTimeApr 20th 2010
     
    Jeff

    What sort of timber do you use over there as piles?

    Evan

    Do you (or anyone else) know what deems a foundation as suitable, is it the mechanical properties of the material, the type of ground it is going into or a combination of both?

    Owlman

    It must be remembered that old houses that are still standing are the ones that have not fallen down, but I am all for not using tonnes of concrete.
  2.  
    There's no foundations at all under the 800mm stone walls of my cottage. With some stones over a tonne in weight there's just 200 year plus compacted earth! And the walls have not moved at all AFAICS.
    • CommentAuthorevan
    • CommentTimeApr 20th 2010
     
    owlman: I have loads of recycled bricks. Anyone know if this type of foundation can still be used and approved?

    ST: Don't know. So many factors involved, largely to do with the ground it's resting on (how much will it settle, how much weight can it bear), and it's difficult to test that kind of thing, so I guess they have a standard formula for strip foundations that can be applied in most ground types (i.e. it's over-built for most ground types).
    And obviously they're going to assume a consistent makeup of the material it's made of: ferro-concrete has a known values of strength, random boulders doesn't :(

    http://en.wikipedia.org/wiki/Bearing_capacity

    I can't afford to start hiring geotechnical engineers so it'll have to be by the book. More concrete, matron!
    • CommentAuthorevan
    • CommentTimeApr 20th 2010 edited
     
    Posted By: BrightgreenThere's no foundations at all under the 800mm stone walls of my cottage. With some stones over a tonne in weight there's just 200 year plus compacted earth! And the walls have not moved at all AFAICS.


    Same here. Well, except at one end where the water tank overflow pipe was dripping down the wall for 20 years, it's sunk a bit :confused:
    •  
      CommentAuthorjoe90
    • CommentTimeApr 20th 2010
     
    I am planning a straw bale build in a few years and there is no way I am using tons of concrete. The alternatives that I am still considering are 1/ Rammed earth in tyres, 2/ Trench filled with crushed stone mixed with stone dust vibrated/rammed every 100mm, 3/ concrete ring beam in insulation on rammed oversite crushed stone mix. Option 3 uses some concrete but a lot less than traditional footings (see http://www.viking-house.ie/passive-house-foundations). option 2/ would probably need a concrete ring beam as well but as 3/ still a lot less than "the norm".
    • CommentAuthorevan
    • CommentTimeApr 20th 2010
     
    That's great but how are you going to do the calculations to prove to building control that it's not going to sink / dissolve / fall over?

    Tell me and I'll copy it :)
    •  
      CommentAuthorjoe90
    • CommentTimeApr 20th 2010
     
    Viking house (option 3) already do this so calc's have been done. Rammed earth in tyres has also been used before for straw bale build and I would probably use Amazonails for structural calcs for the whole build anyway. option 2/ just seems to be a practical solution, well compacted stone/dust sets like concrete and if the structure is timber frame/lightweight then it should suffice. But as you point out I have to prove it to the BCO. I am glad I have three options.

    Anyone else out there good at loading calcs?
    :bigsmile:
    •  
      CommentAuthorjoe90
    • CommentTimeApr 20th 2010
     
    What about Building Regulations?

    There are three buildings in the UK that have both planning permission and building regulation approval for rammed car tyre foundations, all designed by Amazon Nails.
    • CommentAuthorfinny
    • CommentTimeApr 20th 2010
     
    Memory bit fuzzy, down a few cups of tea for this time of the day, but somewhere recently I read about a supermarket built on soft and sketchy ground where the foundation solution was to dig deep pile holes and backfill with graded pebbles, all same size, battered a bit til they locked in, then concrete pads on top. Apparently this technique, borrowed from somewhere clever satisfied building regs and really works. Hope someone out there knows more than me cos I like the idea and wanna know more..
    • CommentAuthorsquowse
    • CommentTimeApr 21st 2010
     
    the technique that will have been used is called "stone columns" and are installed with a huge vibrating poker. they are generally classed as "ground improvement" and are designed and guaranteed by the company to increase the bearing capacity of the ground to allow pad or strip footings to be used instead of conventional piling.

    as regards trench foundations there is a huge difference between compacted rubble and either brick/stone walls laid directly on clay or concrete strip footings.
    masonry buildings are very flexible and able to accommodate differential settlements. i daresay the same for strawbale. you will need to mend the cracks in the plaster though.

    all foundations would have to be signed off by a chartered civil/structural engineer for building regs unless they are the one size fits all approach for smaller buildings in which case an architect or similar may be able to do it.

    brick is not generally accepted as a suitable recycled aggregate for concrete, but this may be your best bet to reduce the environmental impact. ie chuck them in the concrete and don't tell any one. foundation concrete will often use waste product cement replacements as standard - ask about PFA, GGBS or flyash.

    option 3 mentioned above - the ring beam is a strip footing but with steel reinforcement to allow a smaller cross-section of concrete to be used?
    • CommentAuthorjon
    • CommentTimeApr 21st 2010
     
    There are ways to get unusual buildings through regs with severely reduced foundations (sometimes none)

    The problem would be finding a SE who is used to working out on a limb and knows how to get around the 'first principles' reasoning of the British Standards (which effectively over-rule Building Regs where you're doing something special). This means someone very qualified (an unqualified SE may have difficulty getting it through regulations)

    The amazonnails method suggested (don't know of them) seems OK for most lightweight buildings founded on a relatively shallow granular or rocky strata.
    • CommentAuthorCWatters
    • CommentTimeApr 21st 2010
     
    I might be wrong but I half remember reading something about building standards of other EC countries being acceptable in the UK. If that's correct perhaps you can find an EC country that allows timber foundations or similar and invoke EC harmonisation rules to get it approved here. There might also be some CE marked foundation system around. Hard for the UK to refuse to allow its use here?
  3.  
    CWatters, as I understand it, while EUROCODES are europoean wide and ment to facilitate hamonisation and easier oppertunities for overseas tendering, Im pretty sure that each countries local regs take overiding presidence.
    You can use Eurocodes as guidelines for your construction but if a local law is stricter, then the authorities can enforce it over and above Eurocodes if they wish too. I think at some point down the road it is expected that each country will eventualy drop their regs in favour of using Eurocodes, but I dont think many in Western Europe are ready to do this yet.
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