New patio with concrete sub base?

[RichieG]

I'm in the process of having a patio built by a builder.

The builder has dug out a reasonable amount of earth and created a sub base using a mixture of concrete and what looks like hard core. The concrete is now curing and the intention is to lay a sandstone flags patio.

I did quiz him about using a compacted hard core rather than concrete but I was told an additional hard core layer was not required for a light use / domestic patio.

However, all the research I've ever done suggests that the sub base should be hard core rather than a cement mixture - so are we going to have problems down the line with this concrete sub base - or is this concrete sub base just overkill?

Finally, it looks as though the builder is intending to lay the flags using a mixture of builders sand and concrete - does this sound right?

Thanks

Richard

[lutonlagerlout]

concrete can be used as a patio subbase but its an expensive way of doing a subbase,type 1 does much the same job
he should be using grit sand for the bedding layer
building sand is way too soft
LLL

[RichieG]

Hi LLL,

thanks for that - however my main concern is that he has created a monolithic sub base that could move / crack (I've been reading http://www.pavingexpert.com/faq_layover01.htm) which will then cause the sandstone flags to crack as well.. Are my fears justified?

Thanks

[lutonlagerlout]

no m8
if there were cars driving over it ,then it might be an issue,but for a garden patio its overkill if anything
most patios are rigid construction with flags ,so its all ok
LLL

[Rich H]

ditto on the soft/building sand, it's what most builders seem to want to use but a sharp sand mortar will be much better.

[RichieG]

thanks guys - that's laid any concerns to rest - I've spoken to my builder and requested he use sharp sand and its not going to be a problem so everything is good