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Housing - New Build: Foundations near trees

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1 to 19 of 19

  1.  
    • CommentAuthorTriassic
    • CommentTimeMay 9th 2014
     
    I'm about to start construction of my 'annexe', somewhere to live on site during the main house build. The annexe will be 24 feet by 16 feet, single storey, timber frame construction and located at the rear of the plot under some existing mature ash and yew trees. The closest tree is about 1m away (I could get it cut down as I have loads of them on the plot and wouldn't miss one!)

    Having dug a trial hole I struck limestone bedrock at just over 1 metre deep. I was thinking of using 12 concrete block piers to support the building. Is this the correct approach when constructing foundations for this type of building near trees?
    • CommentAuthorowlman
    • CommentTimeMay 9th 2014
     
    I dug out, or at least I thought I had; an Ash tree, 25 years ago when I built a workshop extension, concrete footings etc., the lot. Every year suckers keep appearing from under the footings, and no matter how I try I can't stop them. The Yew tree I wouldn't worry about so much. Ash and sycamore though are like weeds IMO, nice wood both of them, and as hardy growing as anything.
    • CommentAuthortony
    • CommentTimeMay 9th 2014
     
    I would traditional trench fill strip down to rock, or if you cant get concrete near strip footings with blockwork.

    prefer tree out, all gutters and soakaways will block if not.
  4.  
    Dont you need to remove a tree way before the foundation stage to let the ground settle etc?
    • CommentAuthortony
    • CommentTimeMay 9th 2014
     
    not if you are on rock, only really applies with highly shrinkable clay and then there is a lot more to it.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 9th 2014
     
    You're lucky, to have found bedrock, so you can keep your lovely trees. Nothing nicer than a tree up against a building's wall. Makes nature seem undisturbed.

    The only relevant question is, will the tree ever disrupt the bedrock under your foundation? I'd think not.

    Sure, you can keep your gutters clear and put up with an occasional falling branch (or tree!).
    • CommentAuthorTriassic
    • CommentTimeMay 9th 2014 edited
     
    Posted By: tonyI would traditional trench fill strip down to rock, or if you cant get concrete near strip footings with blockwork.
    The existing dilapidated bungalow on site has this type of foundations and the soil below is bone dry and nothing is growing through. So maybe this is the way to go, based on site experience?
    •  
      CommentAuthorfostertom
    • CommentTimeMay 9th 2014
     
    I'd favour isolated piers, ground beams (of railway 'crossing' sleepers if the building isn't masonry) to allow the roots freest (looks odd - free-est?) passage and least disturbance.
    • CommentAuthorShevek
    • CommentTimeMay 9th 2014 edited
     
    Posted By: fostertomYou're lucky, to have found bedrock, so you can keep your lovely trees. Nothing nicer than a tree up against a building's wall. Makes nature seem undisturbed.

    When I worked for an architect in NZ we often designed our houses around trees. Made the buildings look like they were meant to be. Mind you it helped that we only needed 300 mm deep pad foundations on timber piles.
    • CommentAuthorPugliese
    • CommentTimeMay 10th 2014
     
    As FT says if possible keep the tree and clear the gutters. We kept all our trees and upon valuation the estate agent commented how the house looked like it had been up for years and that it enhanced its value by at least 10% and the 'kerb appeal' by 100%.
    • CommentAuthorTriassic
    • CommentTimeMay 15th 2014
     
    So thinking about a building on piers a little more.

    How much clearance should I have between the ground and the underside of the floor cassette?

    How should I prepare the ground below the building:-

    1 Remove tops soil only?
    2 Remove soil and stone, how deep?
    3 Remove soil, geotextile and stone?
    4 Do none of the above and leave ground as is?
    5 Something else?
    • CommentAuthortony
    • CommentTimeMay 15th 2014
     
    I would remove the topsoil, add 100 hardcore poly and 50mm blinding concrete, with 150mm clear of a very well insulated floor cassette
    • CommentAuthorTriassic
    • CommentTimeMay 16th 2014 edited
     
    Posted By: tonyI would remove the topsoil, add 100 hardcore poly and 50mm blinding concrete, with 150mm clear of a very well insulated floor cassette
    what is the reason for this, looking under the existing 1935 vintage bungalow it just has very dry soil below it. Just curious?
    • CommentAuthortony
    • CommentTimeMay 16th 2014
     
    It is not necessary but is good practice, helps keep it clean, resists vermin, probably part of building regs to have an oversite too
    •  
      CommentAuthorfostertom
    • CommentTimeMay 16th 2014
     
    I'd like to think it's just customary overkill, and that the 1935 bungalow solution is adequate. Even if a hotbed of vermin, are they going to jump up and eat into the floor structure?
  16.  
    For what its worth, France regs say you need minimum space of 20cm, for ground movement.
  17.  
    I would leave the ground open and permeable, either just earth or a bed of gravel.
    • CommentAuthorTriassic
    • CommentTimeMay 17th 2014
     
    Posted By: fostertomI'd like to think it's just customary overkill, and that the 1935 bungalow solution is adequate. Even if a hotbed of vermin, are they going to jump up and eat into the floor structure?
    we live in a rural location and we've never had vermin in it under the bungalow. The area is limestone so where would you put the radon barrier, in the floor cassette?
    • CommentAuthortony
    • CommentTimeMay 17th 2014
     
    probably no barrier needed, ventilation of the void will do it.

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