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Variable cavity size, and render bridging DPC

Discussion in 'Building' started by garyo, 10 Mar 2010.

  1. garyo

    garyo

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    Hi,

    Having submitted my full-plans building control application on the basis of a bog standard 85mm cavity wall, brick outer, block inner, I've realised that I wanted to match the brickwork on the existing house. It has two strange features that's I've been stupid enough to overlook until this point:

    1) Below DPC the wall is rendered in what looks like cement. This isn't an issue, but the render finishes around 5mm above DPC - i.e. bridging the DPC. Would this be allowed today? Looking at the photo below, it seems as though it's tapered in to finish exactly at the top of the mortar course that encloses the DPC.

    2) As you can see from the photo, the first four courses of bricks above DPC are 15mm proud of the rest of the wall - i.e the cavity is 15mm larger. I'm not sure if I should attempt to match this. If I did, would I simply start laying the bricks 15mm offset on the fifth course, or would I need special wide bricks, or support piers in the inside of the wall? From an insulation point of view would be acceptable to use 85mm cavity bats in a 100mm cavity?


    Thanks

    Gary
     
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  3. noseall

    noseall

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    A 15mm offset or overhang is acceptable.

    Your internal block-work (if you decide to use full fill drytherm or similar) will need to start out at 115mm at low level then this will become 100mm as you build above the inset plinth.

    So what i am saying is rather than start out at 100mm then diminish to 85mm, start out at 115mm and diminish to 100mm.

    A rendered plinth would be frowned upon today.
     
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  4. garyo

    garyo

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    Okay - so I'd have a consistent cavity size throughout, and it's the blockwork width that varies.

    I may forget about the rendered plinth for now. My concern is that the red engineering bricks might jar against the orange facing bricks, but there'll be a 20cm soil border around the permimeter of the build for plants etc, so I think I'll wait and see.
     
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