Is my contractor ripping me off? - Indian sandstone patio being laid

[mrsdiy]

I think I already know the answer to this but it would be nice to get a few other opinions. We are laying approx 80 sq metres of Indian Sandstone for patio. The contractor has cleared the site of a few raised beds etc and demolished an old conservatory base which was broken up and laid in the excavated part. The path around the house was left. He then filled in the void with 'soil' up to the level of the path. He then put down about a minimal layer of scalpings. I estimate approx a bare inch. He tamped this down and then commenced to lay my flags on a sand/cement mix of approx 1" in part if that. I have photographed the whole thing from start to the point where I asked him to stop work until I had consulted a few builders for second opinions. He told me this sand/cement mix would 'go off' in a couple of days. Nearly two weeks later the flags are rocking and loose and lots have voids under them if you lift them up.
What in others opinions is the bare minimum base you need for these flags. His argument is that everyone will lay them differently which doesn't make his method wrong. He also says it's only for pedestrian use anyway. Well if it wasn't for pedestrian use it would be called a 'drive' as far as I can see. I have as I said photographed the progress and could post? or send these onto anyone who would like to see them.
I am in the process of trying now to work out how much I am prepared to pay him which in my opinion should be up to the point where he went wrong as I now have to get someone else in to start all over again. All four builders have basically said a minimum 4" base of scalping with a 4" approx screed then a sand/cement mix of 2" to lay flags on.
Would appreciate any comments/opinions on this as I feel this guy is taking advantage of me because I am female and he basically said that I didn't know what I was talking about.

[Tony McC]

For a patio, the flags should be laid on 35-50mm of grit sand and cement. I prefer a 10:1 semi-dry mix, others prefer slightly more cement and/or moist or wet mixes.

A sub-base is NOT essential, as I wrote a few moments ago, unless there is a need for excessive build-up, in which case it should be a proper sub-base, not a blinding of soil and an inch (25mm) of whatever these 'scalpings' might be.

Have a read of Do I need a sub-base FAQ

[mrsdiy]

OK have read that link about the sub base. It makes sense but what is worrying me now is that he has used all these large lumps of brick and cement to fill in the large void where he dug out the beds etc which means that by covering it all with soil there are voids which in time will settle and make the patio unstable. I think the main problem we have is that if a sub base is not needed then he shouldn't have dug down so far into the soil where it wasn't necessary. Do you think it would be best to excavate where these lumps of brick and cement are and remove them and level out the soil and build up with scalpings?

[mrsdiy]

Ooops pardon my manners, forgot to say thank you for the reply and help.

[Tony McC]

I'd probably just get rid of the soil, and then 'blind over' the bricks and rubble with a layer of 20mm to dust, rattle it in with the plate compactor, and then build up with additional sub-base quality crushed material as required.

The reason why a sub-base is essential beneath a driveway but not beneath a flagged patio is all to do with loadings. All block paving needs a sub-base because the paving relies on relatively small units and a sub-base helps spread the load. A flagged driveway has a sub-base because a sub-base is very effective at dispersing the loads imposed by heavy cars. However, for a flagged patio, the size of the units is usually sufficient to spread the load of your avergae Yooman Bean and a wheelbarrow, so there's no great need to include a sub-base, unless the ground is really crap to begin with, or, as I've said, you need to build-up levels.