Slab base for playhouse - Slab base

[anakin]

Hi

Have ordered a 10'x5' play house and have cleared an area at the top of the garden for the base. However, I keep reading conflicting advice about how much preparation is needed for the base.

The area had a pile of angular gravel from our old driveway on top of some dirt and the soil that was under this is fairly well compacted.

Part of the lawn that was layed a few months ago also impinges onto where the base will be. When flattening out the area I had to lift out a few big rocks and stones from the back of the base. Consequently, these two areas of the shed base to the front and rear will have low soil compaction.

I am going for the slabs on sand and cement method but I don't know if I need to dig deeper and put down a hardcore/scalpings sub base first.

Or would that be overkill??

If I could use the existing angular gravel as part of any base material that would be useful, seeing as its free and piled next to where the shed will be!

Thanks in advance for any help

Regards

[Tony McC]

Not sure where the conflictiong advice is coming from, but there's a fairly straightforward FAQ regarding the need for a sub-base beneath flagged areas on the main website.

You might be able to us ethe salvaged angular gravel, but does it ahve sufficient fiines to function as a sub-base material, or would it be better mixed with some fine aggregate, a few bags of cement, and laid as a cement-bound material (CBM) sub-base? I can;t see the stuff in question so I can't really comment.

[anakin]

Thanks for the feedback

The conflicting advice was not to bother with a sub base at all for a shed and just lay the slabs onto drymix sand cement without bothering to have a compacted base. Obviously it would be easier if I didn't need to bother but I was just trying to guage what people normally do when building shed bases.

The gravel has no fines but a bit of dirt in it. Would it work as a base if I mixed sand in to some ratio and compacted it? I imagine not but its worth asking.

Failing this I guess I need to order in a bulk bag of scalping and hire a compactor.

Regards

[Tony McC]

No - mix with sand AND cement to make a concrete. sand and dirty gravel isn't really a structural material.

[anakin]

Thanks Tony

So I could put down a concrete base using the old gravel and then put the slabs on top using a dy sand cement mix?

What do you recon would be a good mix ratio and depth would be?

Hopefully I get cracking with this now before they deliver the shed!

Regards

Neil

[Tony McC]

Remove as much crap as poss from the gravel, then mix it with sand and cement in a ration of approximately 6 parts gravel to 3 parts concreting sand to 1 part cement, and lay the flags on 100mm of that.

"Moist mix" is probably the answer to your next question.