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RE: Travertine vs. Porcelain tile -- Which is best for floor? (Follow-Up #14)

posted by: mindstorm on 05.26.2006 at 09:35 am in Kitchens Forum

To answer a previous question - porcelain is VERY hard, even more so than some granites, so you will need a wet saw to cut porcelain. There are some ceramics that I think you can score and cut but I don't know much about that.

Re: determining the stiffness of the floor: Do you have a wood substructure or concrete? If its concrete, I don't know what the mechanism to find out deflection - except the mantra that: "its probably stiff enough!". If it is joists and beams, there are tables that can tell you depending on whether they are metal joists and beams or wood. The numbers L/360 and L/720 connote the expected deflection per foot of joist length for a "typically worst case dynamic load" (i.e. someone walking around on the floor). This is determined in addition to the expected static load (from your furniture, walls, cabinets, fridges etc.). "L" in the ratio above is the length of the unsupported joist under your kitchen. If your "L" is too long (or your joists are too thin) and L/720 for your particular joists turns out to be a bigger number than the stone deflection tolerance (stone wants a very rigid subfloor, porcelain does too but it can tolerate a bit more flexion in the floor, vinyl - well, you can put it on a trampoline I think).

To calculate: If you are like me, you will go dig up the entire elasticity-load-deflection equations, find the type of lumber you have forming the house, find its Young's modulus of elasticity, etc. and determine the elasticity. If you're smarter than me, you will first dig a little and find out that John Bridge's website has a handy-dandy deflecto-meter rigged to his website where you can enter in the size of your joists and beams and out will pop your expected deflection and a stipulation of whether or not your kitchen meets the magic threshold! You'll also know exactly what your expected deflection is so that you know that if you're only just a little bit shy of the L/720 mark if you think you are brave enough to take a chance on travertine. Miy deflection calcuations showed that I was well above the L/360 point and well shy of the L/720 mark. So I knew that I'd need to shore up my joists to install the limestone that I was thinking about. But since I was well above the porcelain stiffness requirement, I decided that I didn't want limestone so badly to be willing to pay for shoring up the joists. ;-)

Good luck.


clipped on: 06.12.2006 at 07:55 am    last updated on: 06.12.2006 at 07:56 am