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    • CommentAuthorPord
    • CommentTimeDec 15th 2017
     
    I'm planning to build a 6m x 4m timber workshop using a Segal-type grid of 150mm treated square wooden posts in post holes approx 500mm square and 600mm deep and filled with concrete. This would avoid having to level the site, as the posts would easily be cut level (in position) at floor height and the workshop built from there.

    I have a few questions regarding the concrete:

    What is the best mix ratio for founds?

    The soil is heavy clay and there is a good chance of the post holes filling a bit with rainwater before I get the concrete in. Is this a problem? Do I need an additive?

    Temps lower than 3-5degC seem to cause problems for curing concrete - as well as covering, is there any other way to mitigate this such as an additive (again)? I need to start the build now rather than wait until Spring.

    Thanks.

    PS am in Scotland.
  1.  
    Hi Pord,

    I am a little confused. The Segal method involves posts *sitting on concrete pads* (with footings below to the satisfaction of the BCO where applicable). The post simply sits on the pad and (in the case of a house, or my sheds) is not fixed to the pad. A piece of lead was used as a DPC between post and pad.

    Your proposal (a ''grid of 150mm treated square wooden posts in post holes approx 500mm square and 600mm deep and filled with concrete. This would avoid having to level the site, as the posts would easily be cut level (in position) at floor height and the workshop built from there. '') seems to involve encasing the posts in concrete. I would not trust even pressure or vacuum treatment to prevent rot in the long term (all my treated fence posts bedded in concrete have rotted).

    I wonder if your bit of Scotland = 'windy Scotland', hence the reason for posts concreted in the ground. What about perhaps an adaptation of the 'Basic Segal' footing with embedded brackets?
    •  
      CommentAuthordjh
    • CommentTimeDec 15th 2017
     
    I'm not an expert but I'd have thought it would be likely to last longer if you made concrete pads instead, with embedded post bases (or bolt-down post bases) and start the timber post above ground.
    • CommentAuthorPord
    • CommentTimeDec 15th 2017
     
    Hi Nick, yes it is for additional strength. I had also assumed the concrete would avoid water coming into direct contact with the encased posts, especially with the addition of Postsaver wraps.

    Concrete pads and brackets would be do-able. My original questions would still apply, though.
  2.  
    OK. 1:2:4 (cement, sand, gravel) if I remember correctly. Others will come in if I don't!

    I had 1:3:6 in mind, but I think that is maybe a more general not-for-footing mix.

    You can buy concrete frost-proofer, but some seem to say they are suitable for footings and some not. Reckon to be OK down to -8 deg C. Wrap top of footing up warm with straw/hessian/blanket/whatever.
    • CommentAuthorPord
    • CommentTimeDec 15th 2017
     
    Thanks guys. 500mm square by 500mm deep sound about right, or could I get away with something a little shallower?
    • CommentAuthorPord
    • CommentTimeDec 15th 2017
     
    Everbuild Zeromix looks like a good option for frost-proofing. Any thoughts?
  3.  
    ''Thanks guys. 500mm square by 500mm deep sound about right, or could I get away with something a little shallower?''


    I don't think any of us could make that judgement, without knowing the ground conditions, but my shed sits on footings about 300-500 deep, on ground that is part-fill, part mud-stone/shaly stuff. It has not moved yet, but every situation must be judged on its merits.
      067.JPG
    • CommentAuthorPord
    • CommentTimeDec 15th 2017
     
    Looks substantial Nick. I'll go for 500mm, I think.

    Is your shed bolted down to the concrete pads?
  4.  
    ''Is your shed bolted down to the concrete pads?''

    No. In that respect it is 'pure Segal'.
    • CommentAuthorPord
    • CommentTimeDec 16th 2017
     
    Ok Nick, thanks. I'd definitely sleep better with a few anchor bolts in place. Hopefully Walter would understand!
    •  
      CommentAuthordjh
    • CommentTimeDec 16th 2017
     
    Posted By: PordOk Nick, thanks. I'd definitely sleep better with a few anchor bolts in place. Hopefully Walter would understand!

    It's a requirement anyway if you're subject to building regs.
    • CommentAuthorPord
    • CommentTimeDec 17th 2017
     
    It's a permitted development, so thankfully no building regs involved.
    • CommentAuthormarsaday
    • CommentTimeDec 17th 2017 edited
     
    This is the start of my shed (8.5 x 3.6m). I have done 3 lines of concrete foundation blocks set on a 100mm concrete pad for each and then mortar. So each hole approx 300mm deep.

    I will be running a ring of 100x100mm treated posts around the perimeter and down the middle line and then building a deck of 125mm treated timber on top of this bearing plate. Need to keep it below 2.5m in total height as close to the boundary hedges. No fire regs imposed on though.
      IMG_1182.jpg
    • CommentAuthormikael
    • CommentTimeDec 17th 2017
     
    Posted By: PordIt's a permitted development, so thankfully no building regs involved.


    As far as I know whether something is constructed under permitted development or not makes no difference to whether a development is subject to building regulations. It will all come down to what the building is to be used for. In technical terms permitted development rules are a default set of planning permissions which apply to every property that has the benefit of them. Building regs apply equally to development carried out under a specific planning consent or under permitted development.
    • CommentAuthormikael
    • CommentTimeDec 17th 2017
     
    Posted By: Nick ParsonsHi Pord,
    I would not trust even pressure or vacuum treatment to prevent rot in the long term (all my treated fence posts bedded in concrete have rotted).


    I would agree. However you could always use precast or prestressed concrete fence posts or lintels instead and cut them down with a diamond saw.
  5.  
    https://www.planningportal.co.uk/info/200130/common_projects/43/outbuildings/2

    Refers to applicability of B Regs to outbuildings:

    ''If you want to put up small detached buildings such as a garden shed or summerhouse in your garden, building regulations will not normally apply if the floor area of the building is less than 15 square metres and contains NO sleeping accommodation.

    If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building contains NO sleeping accommodation and is either at least one metre from any boundary or it is constructed of substantially non-combustible materials.''
    • CommentAuthorPord
    • CommentTimeDec 18th 2017
     
    There is definitely no BC involvement in this build. It's an agricultural shed built as a permitted development within boundary and size restrictions.

    Nice start Marsaday, would be nice to see more pics as you progress.
    • CommentAuthormarsaday
    • CommentTimeDec 18th 2017
     
    Ok Pord, i will try do some updates. Got the soakaway dug out today and the pipe run.
    • CommentAuthormarsaday
    • CommentTimeDec 23rd 2017
     
    Got the joists in and have done 2/3rds of my ply sheets now.
      IMG_1202.jpg
    • CommentAuthorPord
    • CommentTimeDec 27th 2017
     
    Looks good Marsaday. Are you insulating the floor?
    • CommentAuthormarsaday
    • CommentTimeDec 27th 2017
     
    No not doing the floor. Will fit 100 cavity wall insulation i have spare in the walls and the roof in the office bit, but i won't insulate the roof in the shed part, although that may change as i go on.

    Got the final sheet in today and started fitting the perimeter base plates and working out my cuts.
      IMG_1265.jpg
  6.  
    Ccccccccold feet! Not too late to sandwich even only 25mm of Pu between your floor and another sheet of OSB.
    • CommentAuthormarsaday
    • CommentTimeDec 29th 2017
     
    Got the back up and half the front yesterday.

    Maybe struggling to get any more done over the next 4 days.
      IMG_1268.jpg
    • CommentAuthormarsaday
    • CommentTimeJan 5th 2018 edited
     
    Got a bit more done in the last few days.
      IMG_1280.jpg
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