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New (to us) house and I want to build a shed. Ground is permawet currently so I'm looking to build it with the floor raised a little (15-30cm) to allow air underneath but I'm also not sure what to use as support for the base.
I'm happy to dig holes and postcrete supports in then build a base attached to those and then rest the floor on the base but what should I use? there seem to be a number of 'systems' available but they seem to be be spendy so I don't want to buy something that's overkill.
Whole shed will be custom built (it's going in an odd shaped corner of the garden) but next to a fence so I need to be aware of overall height restrictions on the building with a raised floor too.
The usual practice is to dig out a little, make a temporary frame then get concrete poured in - wouldn't that be the simplest solution?
mini-piles.
dig a hole, 6" cardboard packing tube as a former.
you can see them at the front of here, and the one out of 16 that I rushed to finish one day and screwed the level up.
Was going to suggest mini-piles. Its what they use a lot on that building Alaska program. Looks pretty easy. Either that or some 4x4 pressure treated timber in a hole with some concrete. No need to buy a "system"
Nice job, Jim!
I dug 3ft holes with standard post hole diggers, packed the bottom of the hole with a tamper type thing, bowled out the bottom to widen the foot.
I used them because I had a sloping site and to pour a slab would have meant either removing tonnes of material from the back, or building up massively at the front. and access was poor. this way there was very little spoil and not much to handball in/out.
As above, concrete piles, cast in place. Make them big enough that they have a reasonable bearing area at the bottom (depends how soft the ground is) and big enough that they will work in compression and don't need to cope with bending stress from wind on the shed, etc. Then they don't need any steel reinforcing, and without steel in it, concrete will last for centuries.
Piling seems like so much hassle compared to pouring in a base - I know, as I have a bonkers Wendy house contraption on a piled base but I only did that as the ground is on a massive slope (some 20 inches or so front to back).
should add there's also some risk of groundwater flooding so raising the shed a bit would server a dual purpose of keeping it dry during the winter but also protecting it from any rise in gorundwater levels.
Those mini-piles look good - is the base frame resting on them or is it bolted on?
Piling seems like so much hassle compared to pouring in a base – I know, as I have a bonkers Wendy house contraption on a piled base but I only did that as the ground is on a massive slope (some 20 inches or so front to back).
on a level site with easy access, I'd have poured a slab every time.
Those mini-piles look good – is the base frame resting on them or is it bolted on?
bracketed in a few places but mostly gravity. if you knew how much that ekki cladding weighed, you know it isn't going anywhere...
The space I'm going to build a shed isn't wet, but is seemingly the only part of the garden with anything resembling topsoil! The rest is all clay, I dug down about a foot on Saturday to get some sol to fill a raised bed and still didn't hit clay, just lovely black crumbly soil!
My plan is to dig out as much of the good soil as I'm ever likely to need elsewhere in the garden (may as well) and then support the shed on council slabs. I don't really like the idea of scalpings/hardcore/concrete. So the plan is 9 council slabs (corners and halfway points) then I've got decking supports (~30cmx30cm concrete blocks with a cross in the top to take ~2" beams) to raise the base off the slabs and keep them dry.
OTOH I've got to remove the crazy paving from the front drive so if I dig a big enough pit and make some raised beds with the good soil it would save having to pay to dispose of that.
i remember being impressed with jambo's shed when i was looking to build mine a few years ago. it made more sense for me to dig post holes, put a bit of gravel at the bottom for drainage, then stick 4"X4" posts in.
i filled the holes with soil around 6 of the posts, but used postcrete on the 2 posts next to the field just for added strength against some off the hoolies we get blowing up the cliff and across the field. its survived a few storms over the years 🙂
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i used a raised 'ring beam' for my floor, covered in decking for the gazebo section, and OSB for shed section. finished product here.
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i went through the whole process from design to finish with lots of help on here, so every thought process and picture is in this thread, it may help if you had any of the same issues as i had to raise my floor due to uneven/sloping ground.
the pics start on page 3.
HTH
sonotubes/forming tubes with galvanised hardware post feet that you can bolt 4x4s or structure to either set in or bolted in place as if that ground is wet its going to make everything in contact wet.
sonotube diameter or bell footing sized to suit the soil.. down to undisturbed solid dirt if poss.
Don't set your posts into the concrete they will relatively fail quickly if the grounds wet like you say.
you'll need more than 2x4s for the floor unless you're building a trampoline.
Also built high enough for air circulation underneath for drying too. I'd suggest you're essentially building an elevated deck with a room on top.
Dug into the clay about 12", poured the ready-mix in.
Added 2x rebar lengths and then sat the lumber on top.
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