Shed base preparation - partly on sloping concrete

8 Jun 2014
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United Kingdom
Hi all, this is my first post so a warm hello to all!

I'm trying to fit a shed/bike store in our garden and the most sensible site for it has a part that is nice, flat shingle but a part that is sloping concrete. I'd appreciate any advice anyone could give on how best to prepare the surface for laying a paved base.

I've no idea why the concrete is there, I think it's purely decorative - as much as a layer of concrete can be - but there's a slope on it for drainage. It's not that extreme, but requires levelling.

The best way to explain it is by explaining the shed and then what the surface is. We're thinking of a 7x4 Pent Bike Store, with the gradient of the slope in the direction of the 7' length. The first approx 4' or so is flat shingle, the last 2 to 3' is the slope. The drop is maybe 2 to 3 inches over this sloped length - nothing extreme, but needs to be flattened.

Does anyone have any ideas on how best to treat this? I was hoping to put paving slabs down as the base, as we may end up moving the shed once we get to grips with the rest of the garden, so I'm not keen to pour more concrete. I'm also reluctant to start digging out concrete!

My initial thinking was to box in a space on the sloping gravel (using just some treated timber) that I could fill with shingle. I see two issues, the first being that the retaining timber will eventually rot and the second that I'd have to taper it to account for the slope which could be a pain.

Is there a more sensible way of doing this?

(I can provide some pictures to illustrate the problem, if useful, and details of the candidate shed if that has any bearing/if links to commercial sites are allowed on the forum).

All advice gratefully received


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A couple of bags of ready mixed concrete would sort this, but you would have to ensure that the base is cleaned up first (pressure washer,wire brush) Even then the concrete might work loose at the shallow end, but it will just become part of the floor in a shed, no big deal.
If you want to go with the timber/shingle, fine. But use treated timber or decking boards, will last a long time.
You could also do a small concrete 'kerb' inside the timber first, to retain the gravel when the timber rots away, (in 15 years time!)
Ta mate

I've bought the treated boards, and I went for some treated timber which came in 2400mm length - so is ideal for 6 lengths of 400mm paving slabs, although I'll need to cut the shorter length to size. Plan is to make up the outer frame with metal corner brackets to hold it all together, cross-brace it with a central run of timber so it doesn't bow too badly and fill with a layer of sand/cement which will support the paving slabs. It'll end up being 2400 by 1600 (6 by 4 400mm square slabs), with the shed 2050 and 1450 on top.

I'm looking to insert a thinner and lower section which will be fixed inside the main frame where it slopes down on the concrete, so the inner section will be angled down the slope and will essentially fill the gap between the main frame and the ground where the ground drops away. It'll look a bit curious as the main frame will be off the ground at the lower end, but the second run of timber inside the frame will 'make the seal' and enclose the sand. I may put a bit of shingle on the concreted section to stop sand escaping through any gaps and to help drainage.

Typically just got home to find the heavens have opened! I'll hopefully get sometime out in garden this evening to size it all out and make up the frame.

Any thoughts on whether this is sensible, and what to look out for, much appreciated

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I'm a bit lost with your description, but you seem to have it all worked out so just give it a go.

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