Building a front Porch - Please help

Discussion in 'Builders' Talk' started by Barn Builder, Apr 13, 2010.

  1. Barn Builder

    Barn Builder New Member

    I have planning permission to build a porch of 2mtr x 2.5mtr onto the front of my Bungalow. The existing house will retain its external door and there will be no heating in the porch, or perhaps a separate small controllable heater maybe.

    Anyway, I really want to have a crack at doing this myself and have built garden walls before, which were quite reasonable and am a competent DIY'er..

    The outside will be rendered when completed by a renderer.

    It will have double glazed window openings on both side walls and a front door.

    So it will be built from blocks, not brick.

    The ground for footings is firm about 60 cm down.

    i) Do you think I should build it using twin skin walls or will a single skin wall suffice?

    ii) Can anyone shed any advice on what types of block to buy for the walls and for below the dpc level?

    iii) I plan to dig down about 90cm and then pouring a strip foundation of about 200mm deep and 450 mm wide. Does this sound ok?

    Can anyone offer any more advice or tips to help point me in the right direction?

    Many thanks,

  2. bigjules

    bigjules New Member

    Just done exactly as you intend.........

    Masonry construction above DPC was 100mm 3.5N medium dense aggregate block to external leaf, 80mm cavity fully filled with Knauf Dri-Therm cavity slab, 100mm 3.5N Celcon block to inner leaf, 12mm plasterboard dot 'n' dabbed and skimmed.

    Below DPC external leaf was red class B engineering brick, inner leaf 7N dense aggregate blocks.

    Can't comment on foundation design without knowing ground conditions but if you copy existing you shouldn't be far wrong.
  3. Farmerss1

    Farmerss1 New Member

    Foundations appear more than adequate for a single storey porch. Try to avoid over digging under the proposed floor area and fill voids with type 1 stone before placing visqueen membrane linking with DPC.
  4. the old un

    the old un New Member

    Note that you have planning, as you are over 3m2, B.Regs don’t apply at present, but tread careful with regard to windows and heater you are going to install.
    Big jules spec for shell is plenty good enough, it brings you up to 0.30W/m2K,, but if it was me, I would increase cavity and insulation to 100mm full fill slabs and float and set instead of dot and dab. I just don’t like dot and dab.
    Big jules spec for footing is 100%, but as you are not a trowel, you will find it easier to run them in commons rather than class B and con blocks
    Founds. Providing no trees or hedgerow in garden, 1.0m is standard depth with standard 750mm deep trench fill con, or as big jules says go to existing bungalow depth, providing that they are not just 450mm deep, as they might just be depending when it was built You are well shy on a depth of 200mm deep con in a 450mm wide found.
    Before anyone contradicts me on the above, I know that these figures are well in excess of BRegs, but you try getting away with anything less these days.
    Old un. For guidance only.
  5. Barn Builder

    Barn Builder New Member

    I really appreciate your replies guys. Thanks.

    I had no idea there were so many different block types. I always assumed just two (below and above ground).

    Does anyone have a useful link to the different block types available and their uses?

    I would be interested to read up on it.

    Thanks again.
  6. ecm

    ecm New Member

  7. Barn Builder

    Barn Builder New Member



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