what size tanking kit would I need for tongue and groove flooring for a 1200X800 tray and which thicknes tray?
It depends on your total shower area. Is 800 x 1200 total size of the floor in your shower or is it extended by drying area? If not, one waterproofing kit will be more than enough. Each waterproofing kit covers 3.2 square metres with 2 layers.
Wet room kit comes with drain already integrated and waterproofed so main points of concern are floor/wall joints. The kit is the best for this as it contains 10m sealing tape, 2 corners and 2 pipe collars. If you can spare the tanking liquid, extra waterproofing is always good and should be used to protect the shower area and splash area (extends the shower area by 500 mm off each edge).
We have 30 days unconditional returns right policy so you might want to buy additional kit and if you don't use it you can send it back to us for a full refund.
If you have any questions I will be happy to help.
David 020 7193 0953