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Decking close to house, DPC??

Discussion in 'In the Garden' started by LongEarsShortLegs, 17 Aug 2019.

  1. LongEarsShortLegs

    LongEarsShortLegs

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    hi there, long story short I'm part way through a major garden overhaul. have 2 retaining walls built, 60+ tonne of spoil removed (some for levelling purposes, some from where the previous owner dumped the footings and building waste from his extension before covering it with a huge decking structure up the top of the garden). I've put down 20ish metres of random pattern paving on the top level of the garden and have another 10 square metres to go on the intermediate level of the garden (heres hoping for a dry bank holiday weekend), then some steps to fabricate before i get to the bottom section closest to the house.

    Which is where i have run into some issues - namely drainage, DPC levels etc. the current patio is only a course to 1.5 courses below DPC. (with a sizeable step (circa 175mm) into the house as it stands).

    If I was to dig these levels down another 150mm to get the 3 courses below DPC then I'm going to have a major step into the house, add to this that at current levels i am also having drainage issues due to the level of the land being higher on both neighbouring gardens - the area had always been damp, its only now when i have scraped back years of detritus/removed wood cladding from the stone gravel boards etc i can see the damp flowing in - but we currently don't have any issues with damp in the house - just the patio soon becomes green and is very rarely dry.

    Now the current drainage into the combined sewer has plenty of space for the fall (granted one of the 2 channel drains is plumbed in 32mm waste pipe)

    I have been thinking about whether i could just deck over the area? leaving say a 40/50mm gap between the decking structure and the house.

    there is enough space on top of the existing slabs to fit a 2 x 6 joist, a decking board and still maintain around an inch or so below the cills. Obviously these slabs and whatever is underneath could be removed and a few inches of free draining gravel laid, with the existing channel drains removed, french drains fitted and plumbed into the combined sewer.

    The issue of course comes that now the decking structure would be above the level of the DPC (although not affixed to it) given the area below it would have much better drainage than it currently does - would there be any issues with this (either with building regs or splash back causing damp)? Potentially as the decking would be surrounded on all sides with structures higher than it(house on one side, retaining wall on the other, then garden fences with gravel boards either side) i could potentially fit something akin to an upstand (most likely a decking board on end sticking up 50mm or so round the edge of the decking structure to prevent items rolling off the decking/water splashing off the decking against the brickwork)

    But to me it would alleviate issues with the drainage problems i currently have as the decking would be above the level of the current damp patio, allow me to have a better level both into the house and to the steps to the intermediate level of the garden. would have an area that is damp less of the year and just simplify things somewhat (digging down to get to the required DPC clearance and maintain falls away from the house would potentially exposing the buried courses/haunchings for the foundations of the retaining wall - foolishly we used the existing patio levels with a decent fall (1:40) an then an inch or so spare to work out the level of the ground at the base of the lower retaining wall). it would also allow me to do whatever i want within reason below the decking level regards drainage (i.e pipes/channels/gulleys fitted wherever)

    There is only 1 air brick (which is currently partially obstructed by the paving) in this area, which i could quite easily work around to make sure it goes out under the decking into a nice big area with adequate air flow between decking boards etc.

    Thoughts? is it stupid/against regulations? or a semi sensible solution? would affixing it to the wall at or above DPC level (not my current plan) cause any issues - as if that is a better solution than leaving a gap i am open to suggestions.

    I've never done much with decking but have built my fair share of stud walls and done plenty of other joinery jobs.
     
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