Patio base size relative to size of shed

6 Apr 2008
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United Kingdom
I live in a very wet part of Lancashire with particularly claggy clay soil that simply refuses to drain. Previous owners put a shed straight onto the soil surface and now, 10 years after moving in, the shed has sunk to such a degree that the floor has made contact with the ground and rotted away, the walls are moving apart and the whole thing is basically knackered.

So I'm buying a new 12 x 8 foot shed and a friend has given me a load of concrete slabs he didn't need. I guess the best solution is to dig down, lay hardcore and then sand and cement on top to create a base to lay the slabs onto, although some people say I could do it without the hardcore.

What I want to know is should I make the patio exactly the size of the shed base, so that water running off the roof doesn't land on the patio, or perhaps I should make the patio ever so slightly dome shaped so that water runs away on all sides?

To make matters more complicated, the old shed was 8 by 6, and the ground slopes down to one of the long sides before levelling off, so this means I'm going to have to dig out a couple of feet to make the flat bit wide enough.

Several times a year, after a heavy shower, water can stand up to, or slightly above, ground level in one corner of the current shed and so I'm going to be putting the new shed 2 feet out over that bit. Obviously my new patio will have to be higher than the current ground level.
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You will need a hardcore base. Make the base oversized, but only put the slabs under the shed, lay some shingle/spa/decorative gravel around the edges. Fit some guttering too.
Get a water butt! Add an overflow that runs into some beds away from the shed.
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Get a water butt! Add an overflow that runs into some beds away from the shed.

If you don't want to collect the water, you can simply attach a hose to the tap at the bottom, leaving it open, but this will remove the water from around your shed and stop it rotting or washing away your patio base.

Adding the water butt and hose will attenuate the flow, so the flow out of the hose will be small enough not to flood the garden if it overflows.

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