Concrete slab for single block wall.

Discussion in 'Builders' Talk' started by luk4sh31, Jul 23, 2021.

  1. luk4sh31

    luk4sh31 New Member


    I"m planing to build the workshop of 7m by 5m. I have already take up 15 cm of top soil and fill this with type 1 limestone and this has been compacted. I'm planing to use c04 and sand and compact it again. Then I will use 6mm wire reinforcement before lying b30 concrete slab (30 newtons).

    My question is would it be enough to hold a single block wall from 4ich concrete block? If there a better way to do it please let me know? thank you
  2. stevie22

    stevie22 Screwfix Select

    What do you mean by c04? What thickness concrete are you planning to use?

    I would probably go for a 100 slab but thicken it to 200 around the edge to form a foundation for the wall. I would use a DPM (blind the base with sand to stop it being punctured by sharp stones) but probably wouldn't bother with insulation unless the 'shop was going to be regularly used/heated (others will disagree no doubt).

    Too late now but crushed concrete is generally cheaper and often better than limestone and of course greener.
  3. luk4sh31

    luk4sh31 New Member

    hello thank you for your replay. I spelled it wrong it is called 804 _ crushed stone I think 20mm to dust.

    I was thinking:
    804 plus sand and compact it
    polythene membrane
    reinforcement on whole slab
    20cm the side with extra reinforcement mic 6 and 8 mm
    10cm floor

    I was thinking adding the insulation on the top. does it make sense? thank you
  4. stevie22

    stevie22 Screwfix Select

    All you need is the type 1 as that should 50 (or so) to dust. We sometimes use poorer quality materials under it in construction but bound material (ie concrete of blacktop) over it.

    I would have the insulation under the concrete if you're having it as then you have a nice thermal mass to help iron out temperature fluctuation but if it's only periodic use and you're going to let it go cold between uses then higher up will give a quicker warm up. Do think about what you're going to put over the insulation though.
  5. Nev Hope

    Nev Hope Active Member

    Never seen a raft foundation with the insulation beneath the concrete before o_O
  6. luk4sh31

    luk4sh31 New Member

    Originally I wanted to build a timber framed workshop with osb on the floor so I could get the insulation under the floating floor but the prices of osb and timber are ridiculous so I'm trying to adapt.

    I don't have too much experience with block work, but someone who own house before me build a single wall well house (2m by 2m) on 10 cm of concrete base. The concrete block are upright. This got me thinking that I could do something similar and attached the external insulation.

    Im planing to attached that workshop to the timber framed pergola so I might convert it into the office in the future if needed. Them two will have the same flat roof.

    When you said it is better to do insulation under the slab you mean to do proper raft foundation? or to do something like in the photo? thank you

    Attached Files:

  7. Abrickie

    Abrickie Screwfix Select

    Personally I’d go over the concrete :)
  8. luk4sh31

    luk4sh31 New Member

    Thank you I have more questions. Is this done with the same type of the insulation you use in floor? like POLYIZO or kingspan FLOOR INSULATION?
    Can I also make the footing more square? or there is a reason to be on an angle? thanks

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