laying well calibrated slate - first attempts !

[simonjay]

OK, I'm a DIYer as far as floor tiling goes, and I'll describe my first attempt at laying some well calibrated slate.
Any tips would be useful, but I should probably get a professional tiler ;-)

Put this in here as it does not just apply to stone.

So, the slates are 600x400 basically 10mm thick, very regular. I divided into smooth (no ridges), medium (lightly riven)
and rough (max 2mm ridges). So not very rough by slate standards.
I've done 2 tiles - one yesterday and one today (don't laugh).

Using dunlop large format and natural stone flexible rapid-set adhesive (3mm to 25 mm build).
The floor is flattish, but with a few high spots to be taken up in the adhesive.
13mm x 20mm round notches every 28mm large format trowel.

I'm not back buttering, since this adhesive explicitly says you don't need to, and also I'd make
even more of a mess ! The back of the tiles are perfectly flat so this is probably OK.

Started with some of the smooth slates.
Yesterday, mixed a bit thick I think, it almost poured, and ended up laying with about 6mm bed, but thats fine as it will make sure
I can take up the slight undulations in the floor. Did not check for voids under - you cannot get the things up due to suction anyway.
Took ages banging with my fist to get as level as possible with the spirit level.
I had mixed enough for two tiles, not quite though and it hard started to set (about 40mins, says workable for 20mins),
so I chucked it. This could get expensive ! Still the tile was very solid the next day and no hollow sound when tapped all over.

Today, though I'd try doing 2 tiles so mixed the same amount. Seemed a bit more pourable than yesterday.
Having watched a video off the dunlop website, poured the adhesive in the middle of the tiled area and tried to comb to the edges.
Pressed the tile down. It was too low, and unsupported at the edges.
What had happened is with the combing and re-combing, I had ended up with the notches not completely filled and also thinning
out at the edges. I had not pushed the tile down that much and you could see it was not properly bedded - no squidging at all.
Time was getting on, but I had to lift it. Very difficult due to suction, thought the slate might break, but I got it up.
In a slight panic (20 mins working time), I slapped loads more down, combed into full notches. Not that easy to get it up to the
edge of the previous tile as you'd think for some reason.
Anyway, I'd probably got slightly too much adhesive this time, and it ended up about 1mm higher than the next tile.
Slate also may bave been slightly thicker. I thought thats not perfect but fine in the context of slate and the adhesive was
setting anyway, so I've left it. A bit messy, so cleaned the slate with a sponge.
Threw some more adhesive away.

I then realised I was attempting the impossible since the slate was not totally flat (its slate after all), and you could see light
under a spirit level placed across it. So one corner was always going to be a bit high !

Anyway what I need to improve:
1. Probably mix even looser, so tile can be pressed down a bit easier
2. Get the right amount on the floor so I can a nice clean run of full notches across the tile area (I've got a new idea of
pushing the adhesive back into the comb with a plastering trowel to keep the notches full).
3. Judge how much to keep the trowel off the floor to ride over slight dips in the floor.
4. Level the thing quickly - I'm going to get a rubber mallet !
5. Get less adhesive on top of the tile.
5. Manage to do more than 1 tile a day.

I found this much much harder than I ever thought. I hope the learning curve is quick.

Simon.

[Rich]

Stick with it, slate is always going to be a little bit up and down. Mixing the PTB correctly is important. If you are finding it tricky with that adhesive, why dont you get yourself some standard setting adhesive and just back butter? This would give you hours to play with it and you would save yourself a fortune

[nybor62]

by the sounds of it you should have slc the whole floor 1st, to get a nice smooth flat surface. ptb is not the right addy imo for them tiles on that floor,
as rich as said get some slow setting addy ,

[simonjay]

Stick with it, slate is always going to be a little bit up and down. Mixing the PTB correctly is important. If you are finding it tricky with that adhesive, why dont you get yourself some standard setting adhesive and just back butter? This would give you hours to play with it and you would save yourself a fortune

Well I've got 10 bags of the stuff, so that is what I'm using !
However, what adhesive would you recommend for a slow setting version ?

Thanks,
Simon.

[simonjay]

by the sounds of it you should have slc the whole floor 1st, to get a nice smooth flat surface. ptb is not the right addy imo for them tiles on that floor,
as rich as said get some slow setting addy ,

What do you think is the correct adhesive ?

The floor is fairly flat and smooth, only a few 1-2mm variations. I dont think self levelling would have helped much. The slate is quite regular but not enough just to follow the floor like you might with flat ceramic tiles.

Cheers,
Simon.

[Ceramico tiling]

I crossed paths with Dunlop Rapid set once before and NEVER AGAIN,,that is the fastest rapid setting adhesive I have ever used.I think if I was going to tile for the first time using that I would use a nice straight edge and plaster the floor with that adhesive (take out voids etc and with a general floor level in mind make the floor as flat and as level as you want it) Then you could prob just use a notch tile for about 4 tiles or so and have time to back butter.I would lay the thicker tiles strait onto the notched adhesive and then maybe play around with the back butter on the thinner tiles. Maybe use the notch trowel on the backs of the thinner slate tiles as well.Sometimes a bunch of very small dabs placed on top of the notched adhesive on the floor will do(as long as adhesive is still wet and workable and tiles are back buttered).

A good trick is to catch the adhesive as it is just hardening and scrape off any high points with the flat edge of your notched trowel.

Hope it all make sense