Timber shed with concrete slab floor

Discussion in 'Builders' Talk' started by Cyberrobot, Jul 5, 2020.

  1. Cyberrobot

    Cyberrobot New Member

    Hi peeps. I'm planning on building a 8"x16" shed right on a concrete slab. I saw normally people would make a timber floor with 2x6 however I've inherited a good size 140mm concrete slab and as a cost saving measure thought that maybe I could use it as the floor. The shed will be a woodworking workshop so not a living accommodation in any way. I am thinking to secure the frame with 60mm anchors. Two sides will be flush with the end on the slab two other sides won't. Here lies my issue. How to waterproof the gap between concrete and the timber frame. Is it even ok to do it this way? I am not planning on it being a forever shed. If it lasts for 5 years I'll be ok with that. Thanks for your input.
     
  2. Bob Rathbone

    Bob Rathbone Screwfix Select

    Normally, the shed wall would overhang the edge of the slab, this would then route the water past the edge and avoid water seepage.
     
  3. Cyberrobot

    Cyberrobot New Member

    I agree. If I did the concrete slab I'd measure it to the shed but I got it from the prev owners and its slightly off the size of the shed I'm intending to build. I'd really like to know what should I do with the sides that are not flush.
     
  4. Peterdevon

    Peterdevon Screwfix Select

    Can you cut the comcrete out with a disk cutter to make it the correct size so the shed overhangs the edge
     
  5. Bob Rathbone

    Bob Rathbone Screwfix Select

    Then the best option would be to lay a 50mm concrete cover on the existing slab that fits the shed size, that would provide a step up to stop water coning in. May be cheaper to use a wooden floor.
     
  6. Cyberrobot

    Cyberrobot New Member

    That's an option. I'd need a large angle grinder with a large disk. It'll probably incur more cost than putting a wooden floor :)
     
  7. Cyberrobot

    Cyberrobot New Member

    How about waterproof expanding foam? I was thinking to cover bottom plates with a waterproof membrane to prevent contact with water and fill the gaps between the wood and the concrete with expanding foam. Would that work?
     
  8. Rob_bv

    Rob_bv Active Member

    Lay the frame on normal 300mm brickwork DPC, then take it up the timbers on either side before cladding, finish off with a bead of mastic all round. Cheap and easy, but it's not going to stop moisture that is absorbed through the concrete unless you seal the rest of the exposed slab.
     
  9. Cyberrobot

    Cyberrobot New Member

    It sounds like I might be better off with a wooden floor resting on some thin paving slabs. Will be cheaper in the end.
     
  10. Cyberrobot

    Cyberrobot New Member

    In case I do find an acceptable way of waterproofing and build the walls on top of the concrete slab what's the minimum depth of anchors I need and how many is enough?
     

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