Weight of marble floor tiles

[martin4533]

Thinking of putting marble floor tiles on a timber first floor. Should I be concerned about the extra weight . Floor joist are 2" x 8" @ 400 c/c , span 3.70m- 19 mm t & g floor boards ?
Also was going to use Ditra matting underneath as I have used before with good results but not on a first floor situation. Would I still need to ply overboard ?

 

[Richard C]

It's a distributed load so in the grand scheme of things, the overall weight increase won’t make a whole lot of difference; what’s really important is that you don’t have an deflection in the floor. You must overboard - 15mm WBP ply is recommended but 12mm is usually sufficient, don’t chance anything less. Ditra matting over the top if you like; won’t do any harm but will increase floor height.

Preferably, I would consider replacing the entire floor with WBP ply, 18-25mm depending on the floor construction; biggish joist span in your case so I would go for 25mm. This will give you a far more rigid base & avoid silly door threshold heights.