I laid my sandstone circle yesterday on a semi dry 4:1 sharp sand and cement bedding layer, buttering with a building sand and cement mortar. I can lift the flags this morning.
When the flags are laid, are they supposed to be fixed in place? Am I waiting to joint or for a longer curing process before the flags are fixed permanently?
Do I need to start again and if so, what should I do differently?
If it's only a circle then yes start again and make the mix wetter. You could apply an sbr/cement slurry bond bridge to the underside of the flags before laying but I don't usually do that if the mix is good then it'll be fine.
Thanks Pablo: can you explain what an sbr/slurry bond bridge is? Also, are you saying that the flags should be fixed down when the job is completed? Should I leave the sharp sand/cement bedding layer down and make the building sand/cement mortar wetter?
My main difficulty is trying to work out how a non-fixed bedding layer (ie. semi dry sand and cement) is ever going to 'fix' the flags. Surely, whatever mortar I use on top of the bedding layer is going to fix to the flag, but not the bedding layer?
Mix a trowel load of cement with SBR (it's like PVA ony better) until you get a tile type adhesive consistency. Then paint it onto the back of the flag before you bed it. It'll stick like buggery so get it right first time. If you can get away with increasing your levels then just relay on top of the old bedding otherwise bust it out. The pointing will not make the flags stick if thats what you're asking.
Pablo - if I were to start again without using sbr (I'm convinced it isn't fixed properly because I'm inexperienced!) - would I do what I did before (semi-dry sharp sand and cement to bed) then butter with a much wetter building sand and cement mortar? I did both on a 4:1 mix.
i think the problem is in the definition of a semi dry mix,it still has t be wet enough to hold its shape if you make a ball of it in your hand
also the pointing helps hold flags in place
LLL
OK thanks Pablo and Lutonlagerlout. I'm going to take the flags up and semi-dry the bedding layer as LLL suggested (wetter than I've been doing it) and mortar with a wetter mix.
It is also important that the mortar mix is well compacted down. The harder the mortar is compacted the stronger it will be.
It would be easy to lay a sandstone circle level for example by putting your slab on top of the mortar mix and making a few gentle taps with the mallet to make it level, but that would not be sufficient. I am not saying you need to smash the hell out of it but you do need to make sure the mortar is well compacted.
Thanks for the further advice - I'll make sure I position firmly! I'm also paranoid about staining - the gear cost a total of £900 odd (2400 setts and two circles) so I don't want to ruin them.
Thanks to everyone who replied - I count myself lucky to have access to this forum cos it's only experts who can help when you're attempting to do something like this!