Laying/relaying a patio

[MassiveJim]

Our garden currently has Buff 'Riven' finish patio slabs with no spacing between them, 4 deep 7 wide 60cm x 60cm slabs.

I want to extend this to 8 slabs deep (so an additional 4 rows of 7 slabs) and also create a gap between the existing slabs and fill with mortar.
This will never have anything heavy on it as it is impossible to get any heavy machinery or cars around the back of my house.
So forst I will need to relay all of the existing slabs to create the gaps, before digging down and laying the additional slabs at the end.
I have pretty much worked out how I will create the slope and mark the area using pegs, spirit level and a long piece of wood

Having spent the last 2 hours googling this thought I would ask here.

1 - what depth should I dig to ?
2 - what do I need to use as a base (ie hardcore/sand or just sand)
3 - do I need to compact the base with a wacker plate.
4 - how much sand/hardcore will I realistically need ?
5 - handmix in wheel barrow or get a mixer from somewhere ?
6 - dry mortar mix or wet for laying the slabs directly on to ?

I do need to dig down and see what has been done with the existing patio but I haven't got that far yet, I want to order materials and know the cost before I start.

 

[malfunkshun]

1 - 150mm (100mm sub and 50mm for the patio itself, you can probably get away with a 75mm base. Actually you can do it without a base at all, but for longevity I would always put a base of some sort down, it depends entirely on what the ground is like.)
2 - Gravel, crusher material. Not big chunks of building rubble. Do not be talked into buying MOT1 grade stuff and it isn't necessary for a domestic patio.
3 - Use a plate compactor and go over it at least twice, watching for any hollows.
4 - for 20 square metres (based on your quoted slab size) order 1 tonne for every 25mm of depth for the base and a bit less than 2 tonne of sand to sit the slabs on, less if you are doing sand and cement dry mix, but then you have the cost of the cement (about 7 bags for the base plus a couple for the dry mix for pointing.)
5 - Depends on whether or not you go with just sand or sand and cement dry mix, if you are just doing sand I wouldn't bother with a mixer.
6 - Dry mix is plenty, about 6 to 1 from memory, but I am happy to be corrected on that (or indeed any of my numbers )

Don't forget to add a slope for run off if, and I assume it is, running up against the house (1 in 60)

I would say that you probably wouldn't need to do anything like all that, but extending a patio is harder because the new bit rarely settles to the same height as the old section. So for longevity I would go with the above, having ripped up the existing and relaid the whole area.
If the ground is good (not old flower beds, doesn't hold loads of water, isn't too sandy or otherwise loose) I would reduce the base to 50mm

 

[MassiveJim]

Having read your post and spoken to a "mate who does patios and stuff"

It seems 6" is going to be the depth we go to
it is only 10m2 though as I do not plan on putting a new base in for the existing patio, all I want to do is relay the slabs with gaps in between.

Not 100% sure about the ground to be honest I think it is quite a mix of stuff, and it probably has loads of building rubble in it which will probably help so long as I don't have to dig a lot of it up.

Ground does tend to be quite wet sometimes as the house is on a hill so water obviously runs downwards towards us.
the fence on the lower side of our garden has concrete posts and gravel boards and the ground there tends to stay very wet so I will be adressing that at the same time (probably use a french drain) as I do the patio. It didn't hold water before I installed that fence, so I am guessing the boards are stopping the water from draining properly. The ground slopes quite sharply as realistically there should be a step between our garden and neighbours, I think I am going to have to raise the gravel boards up somehow but not sure what I can do without it looking odd on the neighbours side (empty unsold new build at present)

 

[malfunkshun]

if you are going to go the full 6 inches then all should be well. The rest of what I said would stand, except adjust the aggregates accordingly.

 

[Cosmic182]

Whatever you do, don't put it on a dry mix. Use a wet mix! A dry mix will never be good, you'll be able to flick every single flag up, not to mention they'll dip over time. Wet mix and you will have no problems, don't lay them on spots either.