Another shed base question

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Discussion

LaserTam

Original Poster:

2,142 posts

226 months

Thursday 25th July
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Just moved in, but the rotting summer hse is too small, and rotting.

Summer house is an odd shape but appears to be on a concrete base. There is also some concrete laid behind it, but to front and sides a patio has been laid, at a guess probably 20+ years ago.

The new shed/summer hse will be bigger than the existing, (will probably be 10' x8') but I don't really want to be pulling up the existing concrete/patio if it's not necessary. Patio looks to be level and sound but the whole area, including the concreted areas are unlikely to be completely level, so I won't be able to just lay the new shed base on top. I don't really want to raise the level of the base too much I.e lay even a shallow slab on top.

Looking for suggestions in how to approach this. I'm thinking small pads of some sort, suitably placed to support the new shed base frame, not sure what to use though. Any thoughts?

Mr Magooagain

10,776 posts

177 months

Thursday 25th July
quotequote all
What about a level course of bricks laid to the same footprint of the shed then put shed on them?

LaserTam

Original Poster:

2,142 posts

226 months

Saturday 27th July
quotequote all
Yes possibly, but would have to be laid suitably placed to support the base, but I want to keep it as low as possible, to avoid a big step up into the shed.

Mr Pointy

11,822 posts

166 months

Saturday 27th July
quotequote all
The first step is to find out how far out of level it is as that will guide what is needed to level the base.

OutInTheShed

9,323 posts

33 months

Saturday 27th July
quotequote all
If there is to be a wood floor or other base to the shed, that probably only touches the concrete in a small number of places.
Maybe it's a grid of 3 x 4 contact points or something?
Each of these points needs to be shimmed to the same heaight, and each needs 'whatever it takes' to stop it subsiding into the ground.

I put in a shed which was sat on 6 brick piers, each pier was a two brick square, about 3 bricks tall with a couple of inches of concrete in the bottom of the hole.
That worked fine, because by the time I'd dug that deep, the ground was very firm and stoney.

It's a shed. If one corner subsides a bit, you will just jack it up and wedge in another shim.

If you make a long strip of concrete to sit a shed wall on, it needs to be much stronger, because it only takes a very small movement to crack a long piece of concrete, whereas two bits of concrete will move independently and be OK.

I built a different shed at a later house on a solid concrete base. I just put a one brick 'wall' to sit the perimiter of the shed on, with a damp course, and some bricks at intervals inside to support the floor.

If I was building on deep soil, I'd have to do something different.

Top tip, get a 2m spirit level.

Also, if the shed is to be low to the ground without free air under it, consider a polythene damp proof membrane under the floor.

LaserTam

Original Poster:

2,142 posts

226 months

Monday 7th October
quotequote all
Roll forward a few months, because this project stalled for a while. But I now have a better understanding of the levels. I took levels in each square foot.

Shed will be 8ft wide, 12 ft long.

From end to end, it's 2cm out on one side, 1cm on the other.
Side to side its 2.5cm diference on one edge, 0.5cm on the other.
Running down the centre of the 12ft length, the patio has a high point (assume by design for drainage), at its highest, its 2.5cm higher than the lowest point.

My thinking is putting a wooden frame down, with beams to be perp to the shed floor bearers and adjusting it to cater for the uneven base. It will take a while, but perhaps better than adding concrete slab on top of the old patio, because it would probably have to have enough depth so it doesn't become unstable (what's the min I could get away with, 10cm).

I could combine this with gunning out the particular high points in the patio along where the beams will sit.

Thoughts please?

wolfracesonic

7,501 posts

134 months

Monday 7th October
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If you don’t mind having the shed sat a little higher, would adjustable shed feet be an option? They keep the timbers clear of the ground and encourage airflow under the shed.

Wickes have these ones.

LaserTam

Original Poster:

2,142 posts

226 months

Monday 7th October
quotequote all
Thanks, could be an option. With some googling, seems there are more options in terms of min-max height, so a mixture of these might be possible.

I think I would still need a wooden frame on top of these, then sit the floor bearers and boards on that. Would save time not having to trim down the frame and the bearers wouldn't need to be as deep.