[trekkor]

The floor will suport that load.

Use 1/4" HardieBacker, embedded in acrylic modified thinset, fastened with 1 & 1/4" roofing nails. Rent a nail gun and compresser.

Screwing down the subfloor is a good plan. Just use 1 & 5/8" coarse sreetrock screws and a sheetrock screwgun. It'll just take a bout 4-5 hours...if that.

The biggest advice I can give, is to use a 1/2"x1/2" notched trowel.
use straight acrylic in your thinset and pre seal the tiles twice before grouting. Then seal them twice more three days later.

This is a HUGE do-it-yourself project, BTW.

If the price you were quoted is by a legit contractor that really has experience and references... Hire him!
That price is ridiculously CHEAP!!!

Look at the slate section on my website in my signiture.


KT