expansion joints in granite floor tiles for area 300sqm

[Dontiler]

I would use the preformed schluter ones for a jobn that size m8.

Over 40 m2 area your should have expansion gaps every 5m if it's heavily used traffic area, schluter does brilliant expansion trim especially for that, if its 1 big area just divide area 320 m2 in 25m2 it will be 12 square sections, between sections should be shluter expansion trim
good luck

 

[DHTiling]

Any idea what screed it going down...? Cement or Anhydrite ( gypsum based) ..?