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Laying Concrete Base for Timber Garage

Discussion in 'General' started by bladebiker, Dec 31, 2018.

  1. bladebiker

    bladebiker

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    First of all Happy New Year to everyone!

    Decided to replace an old shed/garage with a new Timber Built (sectional) one. The size is 20 Feet by 20 Feet and I need to put down a concrete base. It will need digging out and all the prep doing as the current shed has only an earth floor and it's not even at that!. Any one on here in the trade have any idea of the cost of this type of work?

    Using an online calculator and assuming a depth of 6 inches I have estimated concrete required to be approximately 6 cubic metres

    Thanks in advance
     
  2. martin675

    martin675

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    Are you going to use a ready mix concrete? Id strongly suggest it! I did a 20x10 ft base this year 6 inches deep but had to mix on site. I used 4 builders bags of mot 1 sub base and 4 builders bags sharp sand and then cement. Cost me around £350 in materials including shuttering.
     
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  3. martin675

    martin675

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    Oh i also used steel rebar to strengthen the concrete and stop it cracking
     
  4. bladebiker

    bladebiker

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    Yes I would be using Ready Mix concrete. I'd be getting someone in to do it though. The whole job that is.
     
  5. gary1966

    gary1966

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    Hi, ask away I do this for a living
    Facebook GKW Groundwork

    You will need 5.4 cubic metres and your better to go for one of the company’s that mix it on site as there’s no time limit.

    150mm is slightly over kill but it will be a good base, the the shed have a wooden floor or will the concrete be the floor?

    Definitely lay a hardcore base and compact approximately 6ton.
    Your going to have a lot of soil to get rid of 8/10 ton.

    Price wise if your getting someone in expect to pay anything from £2300/£2800 x vat

    If I can be of any help with advice ask away.
     
  6. bladebiker

    bladebiker

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    Thanks Gary that’s great just the sort of info I was looking for. It’s a pity you are at the other end of the country from me ! I would be using the base as the floor with possibly some rubber matting or similar on top. The timber shed is costing £5/6k so it sounds like I should be comfortably within my budget of £10k.
     
  7. gary1966

    gary1966

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    Yes 10k is about right, if the concrete is the floor on top of the hardcore cover with 1200 gauge dpm polythene and if budget allows then put 50mm thick celotex then the concrete, on my man cave that’s what I have done and then used the plastic garage floor tiles I then used 50mm insulation with 12mm ply over the top on sides and roof on the inside, I have no heating and it’s toastie warm. Don’t skimp on electrics either but on a shed your size if getting electrics done by a professional you can soon spend over £1000. Gary
     
  8. gary1966

    gary1966

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    Also don’t go above 2.5 metres high from floor to top of ridge unless your getting planning permission??
     
  9. bladebiker

    bladebiker

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    It’s actually replacing a timber framed metal clad shed with an earth floor. The good thing is there are already electrics in there and a water supply. Plus my neighbour is a sparky so I think I’ve got that covered. I like the sound of the insulation that you’ve done. Once again many thanks for your input on this it’s been really useful. Just need to get some quotes sorted now.
     
  10. bladebiker

    bladebiker

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    As it’s replacing an existing structure I don’t think I will need any planning permission but I will check with the Local Authority. They sometimes do things differently up here in Scotland!
     
  11. gary1966

    gary1966

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    Insulation is definitely worth doing you will only need 12 sheets but if not doing this definitely lay the polythene. As said before 150mm thick is over kill you could do 150mm at the edges and 100mm over the rest of the floor just depends what your going to be doing in the shed weight wise?
     
  12. bladebiker

    bladebiker

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    Weight wise it will have to deal with a largish car plus my 2 bikes in which case do you think 100mm would suffice. It’s really a garage / workshop.
     
  13. gary1966

    gary1966

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    150mm is what you would use on a commercial premises again if budget allows 150mm is best but it can save you a few quid plus less soil to dig out and get rid of

    View attachment 47649
     
  14. gary1966

    gary1966

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    150mm is what you would use on a commercial premises again if budget allows 150mm is best but it can save you a few quid plus less soil to dig out and get rid of.

    Concrete wise go for a mix of RC25 and if they do it ask for fibre mesh to be mixed in as well.
     
  15. bladebiker

    bladebiker

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    Cheers Gary and Happy New Year
     
  16. bladebiker

    bladebiker

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    Hi Gary hope you are well. I’ve at last got the shed up and have insulated the walls with 50mm sheep wool insulation with 1.8 mil ply on top. I’ve got some celotex to do the roof with 50mm again. The roof is quite high and has a fairly modest pitch. I understand the that a I need to leave an air gap of 50mm between the roof deck and the celotex. I was thinking of attaching the celotex across the face of the rafters rather than in between them which would give me the necessary air gap. Can’t seem to find an answer On Line so just wondered if you had a view.
    Many thanks in advance

    Peter
     
  17. gary1966

    gary1966

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    I done the same and it’s been spot on
     
  18. StMarks

    StMarks PTG

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    That air gap is to enable any dew points, caused by condensing of warm internal air reaching cold external surfaces, to be evaporated.
    The indicated 50mm is to ensure that the gap is unlikely to become obstructed, far less is actually needed.
    However if your ceiling height is adequate, then underdrawing the rafters with the sheet insulation is actually preferable to fitting between. As well as the copious ventilation tunnels that will be left, the rafters themselves will no longer be bridging the insulation. It may also be easier to achieve a tidier finish.
    Hth.
     
  19. bladebiker

    bladebiker

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    Thanks Gary sounds a plan then.
     
  20. bladebiker

    bladebiker

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    Thanks for that. It will make the job a lot easier as ceiling height is not a problem . I will tape the gaps with aluminium tape. I’ve got some specialist washers to stop the screwheads going straight through the Celotex sheets and can screw into the rafters. Don’t need it to be as warm as the house just warm enough to work in.
     

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