What do I lay my flags onto?

[Tom]

OK, thinking slightly ahead, what do I lay my limestone flags onto? I've got a LECA / Limecrete floor with UFH. Do I just bed them onto sand or sand and lime? If sand and lime, what ratio? And do I do a dry or wet mix? Also, I want the joints as tight as possible. How can I achieve this while still getting whatever mix I use in between? My builder's already saying it's going to be difficult and I'll have to leave a larger gap but I don't want that...I don't really want anything much more than, say, 5mm. Is that possible? My friend had her floor done and her builder left 25mm, and more, gaps...it looked awful!!! Thanks for any advice.

Hope your Christmas is going as planned

Jaqy

 

[biffvernon]

I don't like tiles and flags with gaps and great ribbons of grout. Just jam them up tight together and then brush or squeeze into what cracks remain some lime mortar and clean off the surface.

 

[Gervase]

To get the joints as tight as possible it's best to chamfer the edges so the flags are slightly undercut. That way you can butt the top surfaces extremely tightly.
As for bedding, dry silver sand will do on top of a slab, or you could do a very stiff mix of 1:5 hydraulic lime and sand - either way, keep the bedding as thin as possible.

 

[Tom]

Thanks for your replies.

Gervase, why does the bedding need to be as thin as possible? The more information I have, the more I can tell my builder that he *has* to do exactly as I say

Jaqy

 

[Gervase]

The bedding is really only needed to accommodate the little bumps and depressions in the underside of the flags, so there's no need to use any more than the difference between the highest and the lowest point on the stone - any more and you're just raising the height of the floor and putting greater distance between your toes and the heating pipes.

It's not essential to have it as thin as possible, but I have seen builders put down an couple of inches of more of blinding sand, which just seems wasteful if you're not having to raise the floor to a specific height.

To be honest, it's the height of the floor that will determine the precise thickness of the bedding - you don't want huge gaps under any doors that open onto that area, but you also don't want them grounding on the flags. Is there another floor in the building or a doorstep that would give you a datum point?

Though, to be honest, any builder worth his salt would check all that for you and get the bedding right.

 

[Tom]

Thanks, Gervase, for your explanation - it makes perfect sense.

We've taken every floor up in the house (upstairs and downstairs) so there's nothing left to determine a point, other than the hearths...so that's what we're going with.

I'm sure my builder has worked in out correctly (we have a smashing guy, who's very switched on to most things) but it's always wise to be armed with ammunition *before* you need it!! And, besides anything else, I love learning new things and understanding *why* I'm doing something...rather than just doing it

Thanks again.

Jaqy