UKC

Concrete pad or plastic gravel grids? 

The grids look an easier solution but do they actually work? 

Watching with interest as I have to face this task soon. I've also been looking at screw piles in order to minimise disturbance of the ground (it's an allotment), but am worried about a wobbly end result! Definitely trying to avoid the slab.

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I plan on using 60 x 60 concrete paving slabs levelled on sharp sand. Easier than pouring concrete and sheds are usually sized to fit in increments of 60cm. 

I've done the plastic click together and fill with gravel squares twice now for two garden sheds. Much easier for me than mixing concrete. If only for small shed you only need to fill outer areas with gravel. Only disadvantage is bit of time required getting ground/soil level and compact as you can. Mine in place for a few years now and all good, reckon they’ll last indefinitely  

Note you can cut the plastic squares to particular size if needed  

edit to add that I think drainage is better with gravel filled plastic squares than co rate as effectively a french drain round the outside, the old shed that I replaced was on concrete and had rotted from the bottom 

100-150mm MOT1/2 well compacted with timber of paving bearers on top.  If using paving, they work well for compacting the MOT if "waggled" edge down on the surface.

I used plastic grids https://www.ibran.co.uk/products/plastic-shed-base over a weed membrane back filled with gravel. For a 16 x 8 foot base, it took me 3 hours to skim off the turf & level, lay the membrane & grids and backfill with gravel (including barrowing 2 tonnes of gravel through the garage and up the garden). A long spirit level is helpful!

I looked into concrete and paving slabs as other options but concluded the grids would be the quickest and easiest option. The other advantage is the shed is sat on a free draining base so is not sat in any puddles after rain.   

If you're not in a hurry you can often pick up free or cheap second hand slabs from Facebook Marketplace etc  

That's one hell of a shed! 😀 

If the ground is pretty solid underneath, you could just put weed membrane and then paving on top of that, if it's a small garden shed.

Whatever you do, make sure you don't leave any potential for rodents to nest underneath.

Ha! I wish!

Six slabs for a 6' x 4' shed. 

Or a long, straight piece if wood and an average level

Yep - I just sold a load of slabs for about £2 each. I reckon the guy would probably have paid more, as he was short to finish a job, but pleased to get what I did and not have to pay to dispose of them at the tip, or even take them there.

Couple of years ago, I got some block paving very cheap from someone else for a small project.

I considered the screw piles as have quite an ambitious big shed refurb to do, but they actually work out quite expensive. After much research I'm going for breeze blocks on a compacted base, much cheaper and very sturdy. 

Assuming ground you're laying the plastic grids onto is reasonably solid / compacted then for a storage shed they're grand.

Edit: you can buy them already lined with membrane or if you're buying it I'd lay out a little extra for the driveway geotextile stuff.

A shed base really doesn't need to be any thing fancy and a concrete slab is overkill imo unless it is actually going to be the floor of the shed. You just need a level, firm, and free draining surface. Slabs tend to a good, cost effective solution but shingle should be fine. The main thing is to allow air to flow around and under it so it can dry out after rain. Nothing will rot a shed faster than permanently damp wood. Use some sacrificial timbers between the ground and the shed base so it doesn't draw water up from the ground and increases air flow.   

I would go for slabs or just a well compacted stone base. I can see little reason to use plastic.

Recently looked into this and followed the advice.

I found a comment on an American site that suggested using gravel, I used type 1 over a membrane.

Reason for avoiding concrete or slabs was the rain splashes up and rots the bottom planks out quicker.

Seemed to make sense and has been effective so far. 

Put an 8x10' shed last year, weed proof membrane, then plastic grid, then gravel. Very easy, shed stays nice and dry.

Thanks - I was rapidly coming to a similar conclusion although they would look very cool and generate a fair bit of allotment banter! Also they would remove the need for cut and fill etc, however there's some risk as with any ground-work.

Those plastic squares are currently sounding pretty tempting to me, although I'd ideally like a bit more height off the ground - they seem to be 40mm deep which isn't much. More research required.

I had to get a bit creative with ours because it's on sloping ground. Rather than try to level it and retain the high side (not happening) we built two sturdy stub walls up to the same level then used concrete lintels across them as the base. It gives exactly the same support as wooden bearers would, plenty space underneath, etc. I did a bit of ground prep and gave some thought to having a super good enough foundation under the walls but it's a shed, not the burj khalifa.

I'm ready to be told I'm wrong but on level ground I reckon a couple rows of well-bedded 4" blocks and some lintels would probably be plenty.

Our shed, 6x8 sits on concrete lintels, there are 6 of them 6 foot long. Holds the shed about 80mm above the ground so plenty of ventilation and handy for critters nesting under it. 

Plastic Adjustable Decking Risers might be an alternative to screw piles.

https://www.wickes.co.uk/Jouplast-Plastic-Adjustable-Decking-Risers---50-to...

They look a good solution!

Not use any of these but found them when I was looking previously.

https://www.shedbase.com/

900 x 600 Council paving slabs ain't going anywhere as a shed base.  Put a weed mat underneath if you want, but not sure it's worth it under a shed.

+1 for concrete slabs on a sand or red blaes base. I did one of those in a downpour for my late dad in about 1990, the day he moved into that house. Hut stayed dry over the ensuing 10 years that I know of, and so far as I know it’s still standing.

That and some postcrete might do the job; seems they do extensions to make them a bit taller. Very good value.

I did a base for a large, 12' x 18' workshop last year with 60x60cm paving slabs on rubble then a sharp sand base (with a bit of dry cement mixed in, so it cures a bit). If you go this route - recommended for a big heavy shed I think - it is definitely worth renting a vacuum slab lifter from a tool hire place. It would have been a nightmare without, and even with it, leveling everything off involved a lot of faffing.

Significantly lower CO2 emissions if you can avoid using concrete, too.  Plastic manufacture and gravel extraction have their footprints too, of course, but I understand that in general concrete is always going to have the greater environmental impact.

What a useful topic. I've had some ground recently levelled for a 4*5m shed/workshop, so will look into these solutions.

I was going to sink concrete piles and put joists on them. It's going onto clay soil which can move a bit.