laying decking on top of existing patio?

31 May 2005
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United Kingdom
I want to put some decking outside my house's patio doors. There is currently a patio there and I want to make the job easy by building the deck on top of the patio rather than having to rip it all up. The one thing Im concerned about is the damp course. Im thinking that if I keep the frame freestanding at the house end and secure it with post at the edge of the patio I dont need to worry too much? The problem is that there is only currently two bricks in height between the top of the patio as it is and the damp course - so am I ok to just keep the decking say 1inch away from the house even though the top level of the deck may be above the damp course?

help!?!?? please?

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Okay, the problem will be that you have by-pass the dpc to prevent damp wall, the only thing I can think at the moment is use wall sealant such as Thompson's Water Seal products for exterior wall (just approximately 6" to 8" above the decking to prevent splash back of the rain) or maybe a cut a groove into the brickwork and fit maybe a 9" lead flashing to the decking level or do they do long narrow flower tub to match your decking maybe against the wall which should collect most of the rainwater.
As you can see in the picture for dpc reason,

Just has another thought, 140mm wide decking (dpc staple to the back) then screw into the wall with maybe a kitchen unit plastic blocks on the back of the decking to act a spacer to let the rain above run straight down behind it, the decking will then look a skirting board.
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This is a problem I have. Both my neighbours have had companies in to do their decking and they have simply fitted it up to the house at DPC level. The deck sits at the same level as the floor in the house which is really nice as it feels like an extension of the house when you walk about of the french windows.

If this is done would it be an issue during the survey should you want to move house?


The "splashback" effect shown on the above sketch would be no worse than rain penetrating.
The DPC is to prevent rising damp, rising from the "GROUND" and not dampness penetrating from outside to in.
If it was a solid patio which was level with internal floor, there would be a risk of water penetration, in the event that the cavity was to be blocked or bridge.
With timber decking, leave a gap of say 25mm between decking and wall, so if levels of decking are wrong, the water will just rund down the patio, as before.

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