Shed foundations

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Hi . I've a 12x8 shed on a 6 inch slab of concrete and I'd like to replace it for something a little bigger. Made the mistake of putting down a level pad so water lays by the floor battens and it's already rotting the base after only 3 years.
So I need to raise it up and make sure the timber is clear . I could run a couple of rows of bricks round and 're erect it on those after fitting new floor timbers but the pad allows a 12 x10 at least so wondering if I can rebuild and go say 18 inches brick base and timber frame on top or whether i need to break up the base and dig footing etc then build up to base height, concrete put bricks down. I guess it's all down to weight but would be nice if I could build straight onto the pad. I should say the 6 inch concrete isint 're enforced and is on about 6 inches of rubble and compacted hogging. Any advice would be appreciated. Thanks
 
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Hi,

You could break up the concrete pad and use this as rubble for the extended pad but it would be a great deal of hard work and you'd still need a new base/pad. Extending the original concrete pad would give a good base but pictures would give a better idea?

I've built two small garden huts and used 3" x 3" fence posts for the floor joists and these are lifted clear of the ground to allow plenty of ventilation under the floor; it makes the huts a bit higher from the ground but it works for me.

We're on a very steep site so the huts are small but lifting them clear of the ground ensures long life; our previous garden hut was second hand when we bought it and it was still in good condition after 30 years with no rot to the floor at all.

Your shed at 12' x 10' is a decent size so what size would you like the shed to be?

Good luck.

Kind regards, Colin.



Garden huts (1).JPG


Just a 3' x 2' flag base with the hut supported on blocks to allow plenty of underfloor ventilation.

Garden huts (2).JPG


The second hut supported on building blocks; the floor joists have plastic DPC between them and the blocks; it doesn't matter if the ground under the hut gets wet because it soon dries out and the hut isn't in direct contact with the ground.

Garden huts (3).JPG


Just small huts 6' x 5' but on decent joists and the huts are fully constructed of 6" x 1" tanalised timber including roof and floor using stainless steel screws. Here I'm just testing for fit and level.
 
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Thankyou for your reply. The air circulation makes so much difference as you say and something I totally overlooked at my cost really. My pad is approx 14 feet square done in 2 halves and it is a lot of work not to mention a waste of money to break this up if not necessary. I'll have a 12x10 or 12x12 and raised on bearers is plenty thick enough to base either but I do like the idea of a low brick or block base and just not sure if I can risk building direct on a straight concrete slab. There isint too much weight difference really as it would only be 18 inches or so high but it feels more correct to dig a trench and build on a footing which is of course a lot more work!
 
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Wood floors need to be off the ground to allow air circulation.

I built this up on bricks on paving slabs so that the base was 9" above the ground. It's all non treated softwood and roofing ply.
There's bits of butyl pond liner between the wood and the bricks.

06_10_0.JPEG


The building has 9" "skirts made from Victorian style skirting boards on three sides. There's no skirt at the back just a wood and mesh screen to allow for good air circulation.
No rain falls on this area because of the overhang of the roof, and some guttering to prevent any rain running down the fence.

P1000618.JPG


The skirts appear to reach down to the path, but finish a couple of inches above it

After 33 years and some regular painting, there's no sign of any rot.

P1060523.JPG
 
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Than kyou for your reply. My shed was supplied with 2x3 base timbers and not sure how well preserved but I can see either way if I 're use the pad I need to get them up in the air and use a form of damp proofing at any contact points
 

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