Travatine load on gypsum - Tile Advice

[Spreadz]

Hi all, first post... So go easy

ive been to look at a job today for customer having an extension built. I have been called in to price tilling there en-suite. Unfortunately it's been skimmed a couple of weeks ago so I'm presented with a fresh gypsum background. The walls are a mix of stud and dabbed masonry.
the tile they have there heart set on is a large honed Travatine tile 30.5x45.7 (by12mm off the top of my head) for the body tile and a mosaic version of this for a vertical strip in the centre of the shower.

My concern is adding the additional load to the skim. I read from the TTA publication that 20kg/m2 is the industry recommendation for gypsum walls.

so I'm trying to find out firstly the weight of these tiles, short of picking up a sample and weighing it is there a formula for calculating the load and any recommendations for perhaps improving the bond or overcoming the problem if they are exceeding the recommended weight for plaster. Without stating the obvious like ripping the skimmed walls back and fixing backers etc...

 

[Gazzer]

I would take a guess that the travertine mentioned would be at least 25kg per m2

http://www.tilersforums.com/tiling-forum/11570-weight-limestone-travertine-per-square-meter.html

 

[Spreadz]

Thanks sir ramic, that thread was a useful read.
so as I see it there are two options;
1. I need to change the customers mind to a man made Travatine look tile to reduce weight?
2. Make alteration to the ensuite changing the skimmed boards

any other options great fully received!

 

[beanz]

There was talk, on here, a while back of the industry standard weights being revised at some point, due to changes in materials since those figures were decided on.. Maybe there's some way of finding out how they're going with the revision!?!