Slate tiles bedding/jointing question

[davemm]

Hi There,

I am planning to lay 60cm x 30cm slate tiles on three stepped levels, approx 1m x 3m each level. The levels were cast in concrete about a two weeks ago. The tiles have been machine cut so have perfectly straight edges.

My questions are;

1. What type & and thickness of bedding should I use to lay the tiles on the concrete base?

2. Is it ok to butt the tiles right up against each other or do I need a joint?

Thanks so much for the site its been a lifesaver!

Dave M.

[lutonlagerlout]

i would always have a slight joint even if its only 5mm
and you need out door tile adhesive
cheers LLL

[Tony McC]

Tile adhesive (outdoor flavour) or SBR/Ronafix enhanced mortar for the bedding/jointing, and yes, you will need a joint.

[davemm]

Thanks for your reply LLL

Would it be ok to use a mortar instead of tile adhesive as the slate tiles/flags are riven and vary in thickness from 20-30mm, so I need some leeway with the bedding to level them.

I'm wondering if the tiles are laid on a continuous mortar bedding on a concrete slab so no appreciable water can get under the tiles if it would be ok to do without pointing. Would there be a problem of water getting between the tiles, freezing/expanding and cracking the tiles?

The person I am laying the tiles for has showed me pictures of installations where the stones appear to be butted right up against each other with no gap. The slates we are using have machined edges so could be pushed right together. In the slate section of this site there are pictures where there appears to be no gap between the slates, (see pic of 300x300mm Dartmoor Grey Slate Tiles)
slate page

I'm guessing that the function of pointed joints is multifold; strength, water proofing, aesthetic?

Cheers,

Dave

[davemm]

Thanks for your reply Tony, I didn't see it before my last post to LLL.

Cheers,

Dave

[Pablo]

Sort the tiles into 3 different sizes will make bedding easier and give a better finish. Stick the nasty ones into the corners and use them for cuts where they won't be noticed so much. Use the best sealer you can afford lithofin is about as good as it gets. You might get away without a joint but the tiles would have to be very smooth. Would take a very good tiler to make a good job of it.

[lutonlagerlout]

try butt jointing and you will soon come unstuck,nothing is as square and straight as it seems
LLL

[davemm]

Thanks for all the input gents! A great help.

The weather is too cold to tackle it right now, so hopefully things will warm up a bit next week,

All the best,

Dave