Restraint of sub-bases

[davidm]

Hello.

This is a back to basics question but can't seem to find an answer, or rather 'rules-of-thumb' for edge restraint on paving projects. I'm about to construct a small patio area, about 4 inches above ground, to be used mostly for pots and have decided on porcelain 'quarry-style' tiles which need to be bedded on concrete. My plan is to excavate 3 to 4 inches below ground level, add and compact type 1 MOT, construct shuttering for the concrete slab and pour concrete (with a dpm to prevent the slab drying out too quickly). so far so simple. I'm simply wondering though, after seeing a lot of examples of this, why eventually the MOT sub-base might be disrupted by ants etc as it is 'unbound' in the same way that block paving sand needs to be restrained at the edges? Shouldn't bullnose edging be used? Or doesn't it matter if no-one is going to be digging too much afterwards near the edge? Certainly the concrete won't move but am interested in long-term stability if the MOT undermined.

Thanks for reading.

[lutonlagerlout]

its a valid question
basically the subbase should be wholly underground
when digging you should remove all topsoil and dig down to the subgrade (clay chalk stone sand whatever)
If we were casting this slab we would shutter it with a TOE around the edge so that the concrete when hard forms the restraint
I hope this makes sense
cheers LLL