you may be able to get away with 9mm if your floor is already solid,

OK, 9mm ply it is. I need to keep the thickness down as it is a wooden
floor. However, it is pretty well solid already and layed with hardboard.

but also cost wise they were reasonably priced (£3.0+VAT/unit), and
also had the 400x400 slates which we wanted.

Hmm. Is that 3 quid per 400mm slate? (i.e. 18.75/m2) I was planning to use
300mm slate at about 1.40 each (15.55/m2), so it would be in the same
ballpark. Is 400mm cheaper, the same or more expensive than 300mm slates? I
think 300mm would look better for us.

They also allowed us to arrange own delivery - (Palletline -
£41+VAT/900kg).

Ah, that could make it more expensive. I'd rather collect for free, if
possible. (My personal transport is a 2.8 tonne GVW minibus, so no problems
shifting it in one load).

Stonell recommended Howtex SS, however we opted for Ardex Ardu-flex
7001 timber system (approx. £30 / bag ), used 10 bags in the end as
had uneven floor.

Ouch. That sounds expensive. Presumably I'd need around 5 bags, then, or did
you lay it on really thick? Are there cheaper sources that aren't too much
of a compromise?

3. How many coats of StainStop and Colour Intensifier should I use?
4. How many litres will I need of each?

The more the better, we bought 2 litres of stainstop, which did 3
coats.

It sounds like a litre should do me, then.

Finally once grouted we 'stainstopped' again, from recollection you
need to reapply every year after that.

Do you stainstop the grout, too?

I think I followed the advice given here (andy hall ?) and went for
grey at 8-10mm spacing, certainly looks right. Again use the flexible
stuff, we used Ardex again - 2x11kg bags (£10-15/bag)

Can you get it ready coloured, to avoid matching problems?

Although it took much longer to do than originally thought, we are
delighted with our slate floor!

I hope to be so soon, too!

So, cost wise, we've got around:

30 Stainstop
10 PowerClean
15 Colour Intensifier
150 Adhesive
15 Grout
50 Plywood
150 Tiles
-----------
420 Total

Does that sound right? Have I missed anything major?

Christian.

P.S. I think I've given up on the underfloor heating idea in favour of an
under cabinet fan convector. There would only have been room for electric
underfloor, and at around 300 quid to install, too. Is the floor
sufficiently warm (on suspended timber subfloor) to stand walking around in
socks?