/ Slabs Sub base

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baileyswalk - on 02 Dec 2018

Just built a new shed for bike pottering and general man caving duties, problem is it’s full of sh*t from the old shed.

Solution = build a hut for shed sh*t so comfy chair and optic, I mean work bench and stuff and things can be added to new shed.

I’ve got some old heavy (50KG or so) slabs that were recently lifted from around the house. These were not cemented in, only laid on ash & then sand –  they were flush and hadn’t moved since the day they were put down (many years before my time here).

So… my slab area is going to be about 4m2 which would be about 0.5 tonne of type 1 and 0.5 of sand. Problem is can’t find anyone locally that will do a half tonne.

So would it be OK to just get a tonne of sand and use just sand?

The slabs won’t be walked on, they will just have this hut on them, also I have no whacker – will stamping in the sub base be good enough? Never done any slabs before…


funkyvin1 - on 02 Dec 2018
In reply to baileyswalk:

Assuming you're planning on putting the shed on previously undisturbed ground (i.e not over an old veg patch or flower bed that has been frequently disturbed/turned over), I think you'd be OK just putting the slabs down directly onto a soil base, perhaps with a little sharp sand to help get the area level. The slabs are heavy and unlikely to move, especially when your shed (presuming it has its own floor) goes on top, as any weight in the shed will be spread evenly over move than one slab.

If you want to use sand (no type 1), mix some cement dust with it (5-6 bags will be enough for a bulk bag of sand). Fill the required area with the mix, roughly level it and tamp down the whole area with a length of timber (easier with 2 people), then screed the area off. The slabs can then be laid directly onto this and left for a couple of days for the base to go off before you put the shed onto it.

There will also be videos on line (YouTube or whatever), that can help you with anything you are unsure of.

Fruitbat on 02 Dec 2018
In reply to baileyswalk:

Keep it simple. What is the ground like that you are laying the flags on? If it's soil or similar then just do as funkyvin suggests and put them straight on that with maybe a bit of coarse sand to make up any low spots, no need for any cement as they won't go anywhere once they're down.

50kg is heavy, are they 3'x2'x2 1/2" ? Do you know how to 'walk' them and are happy moving them around? Do you have a maul to level them? (I'm a time-served paviour, just want to make sure you'll still have all your fingers for climbing, not trying to put you off).

Edit: seen your post on STW, shouldn't be any need for a wacker or stone etc.


Post edited at 14:17
baileyswalk - on 02 Dec 2018
In reply to baileyswalk:

OK - contradictory to STW but it makes sense to me, its not getting walked on after all just a static weight of the shed on it (more like a small hut thing). Those bikers love to over engineering things.


No idea how to walk slabs etc.

They are 2' x 4' x 2" I'm happy moving them about but dont like the idea of nipped fingers! Will google how to avoid that...

Got a good pinch bar but nae idea what a maul is, again assuming google is my friend here.

Cheers for the advice to u both.

Fruitbat on 02 Dec 2018
In reply to baileyswalk:

You are right saying that they are over-engineering it - I've seen it quite a lot on STW, here and elsewhere. Nobody is wrong as such, just a bit cautious and it's just making work for you.

This is a maul You might be able to hire one, they are not that expensive to buy but all the new ones seem to be solid rubber which bounces, unlike the old string+rubber ones which put the energy into knocking the flag down. I dont know what you could use effectively as a substitute. You might have a chance of picking up a second-hand one (especially in a big place such as Glasgow,  assuming your profile is correct).

Some info on lowering the flags into position here Can't find any info on walking flags, it's one of those things that is a hundred times easier and quicker to demonstrate than to explain. Avoid lifting and carrying the flags, to save both your back and the result of one breaking.

Good luck. Give me a shout if you have any more questions. 


Post edited at 20:51
dingbat46 - on 02 Dec 2018
In reply to baileyswalk:

You can buy Type 1 in 25kg bulk bags, admittedly not the most cost effective method but 20 bags would give you what you need.

Buildbase will do them.

DenzelLN - on 02 Dec 2018
In reply to Fruitbat:

Im a member on that site funnily enough, have been for around 11 years.

I wouldn't bother with the Type 1 or the sand tbh, id order half a cube of 10mm ready mix - semi dry concrete from a mimimix company.

Put that directly on the earth/sub grade and lay your flags on to that, the depth of the dry mix will allow you to gently knock you flags down to level.

No wacker/type 1/sand/massive maul needed, you will need something to tap them with, i use a dead blow hammer, but you could use any hammer and a heavy piece of wood end grain on?

Post edited at 21:01
Fruitbat on 02 Dec 2018
In reply to baileyswalk:

Well, baileyswalk, a few more suggestions have been made. It's up to you, but all I will say (again) is 'keep it simple'.


baileyswalk - on 02 Dec 2018
In reply to baileyswalk:

Cheers folks, got a week to sort this sh*t show out so will report back for anyone that may stumble upon here in the future.

Jmacquarrie - on 03 Dec 2018
In reply to baileyswalk:

If you do decide to use Type 1 then just a tip - don't rake it, use a shovel to pull it about or you end up with a pile of all the bigger stones that then won't lock together.

Personally I'd keep it as simple as possible as many others have suggested.

Rick Graham on 03 Dec 2018
In reply to Jmacquarrie:

Yes, keep it simple.

My 6*8' shed was laid on flags placed directly onto soil over 20 years ago.

Its still there.

Just ensure no timber is in contact with the ground. Some timber pads / shims separated by DPM from the flags can be useful. Being lowest they will rot first and can also be replaced ( one at a time using  wedges ) or adjusted if some flags settle over time.

Jmacquarrie - on 03 Dec 2018
In reply to Rick Graham:

Concrete fence posts laid flat make excellent bearers, not as cheap as wood of course.

baileyswalk - on 05 Dec 2018
In reply to baileyswalk:

Shed build underway, so far so good.

For the paving I dug it out then added a wooden border. Next, papped down some weed barrier & on with 8 bags of sharp sand, then laid slabs. Hindsight... should have dug it out a bit more, slabs are sitting a bit higher than thr wooden border - but I'm ok with that.

One slab has a bit of seesaw action if u rock it but it will br grand for a hut base. Took one day to do all that, minimal effort.

The only thing I'm left contemplating is how to keep thr base off the paving stones... got some spare slabs so think i will cut them to the width of the timber then lay them under the base with some dpm in between. So far it's going far too well, disaster cant be far away!!

Jmacquarrie - on 05 Dec 2018
In reply to baileyswalk:

I'm sure it'll be fine, sounds like it's gone well so far and having a bit of slab above the edging doesn't cause any problems.

I'm currently trying to work out how to get 4.5m³ of concrete to my slab frame, it's about 100m from where I can get the mixer lorry to and the ground is pretty sodden so even just a 1 ton dumper will rip the garden to bits after 10 odd trips back and forth...

Post edited at 18:07
DenzelLN - on 05 Dec 2018
In reply to Jmacquarrie:

High lift mini track dumper, might be a little kinder to the grass?

Jmacquarrie - on 05 Dec 2018
In reply to DenzelLN:

Going for a tyre based dumper I think, only get 30 minutes with the mixer lorry and then they start charging at £3+ a minute or something silly so tracked would take too long.  This is for a commercial job as if it was my garden it would wait untill spring!

Post edited at 18:17
Fruitbat on 05 Dec 2018
In reply to baileyswalk:

All sounds good. Don't worry about the flags being higher than the edging - better than them being lower, and it allows for a bit of settling.

Thanks for keeping us updated - loads of threads in which people ask for advice but never then come back to say if it was useful.


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