Advice on what base to use please! - Concrete base vs usual bed & sub

[AlanaM]

Hi all, I'm hoping to have my patio laid soon, I've got black limestone flags (Black Kadapha from Pavestone) they're only 600x300 so pretty small and I read on this website that usually thinner stuff is more like a tile than a flag..
I thought they would be good on a regular base of hardcore wacked down and then quite a moist mix of sand & cement like most the other advice on here... my dad thinks it will be a better job and last longer if we first put in a concrete base and then lay them on top with a thinnish very wet mix.. more like mortar to make sure they stick and won't come loose. I suppose it's more like laying slate flags inside a house on concrete floor. He says because they are so small I might have more issues with movement/ sinking etc and wants it to be properly done and last for many years etc.
Just want to know from anyone who's installed such things is a concrete base the best way to do it or is it overkill?

Any advice greatly appreciated!
Alana

[seanandruby]

Maybe best to lay as described for porcelain tiles/slabs see here

[lutonlagerlout]

but there are Limestone!
I wouldnt lay a concrete base first as this is fraught with danger
the biggest one being it tends to cause a raft of problems
10-150mm type 1 wacked in 2 X 75mm layers then 35-50mm of wet 6:1 mortar with SBR added
also a SBR bond bridge added to the back of each flag before laying
the concrete base whilst seemingly a good idea is difficult to achieve 100% and is unforgiving when cured
cheers LLL

[Tony McC]

You could use a concrete base, but it's probably over-engineering for such a relatively simple job.

LLL's suggestion is sound, but be aware that Kadapha Black is prone to fading over time and you may want to consider preventative action.

[AlanaM]

Thank you all for the advice!
Also Tony RE the fading I did come across the page on here about black limestone which gave me a bit of a surprise but I'll definitely be getting a decent sealant and keeping on top of it
Cheers