Cutting 35" Porcelain tiles? - Page 2 - DIY Chatroom

diy'er on LI · 11-03-2009, 06:43 PM

Quote:

Originally Posted by R&D Tile

diy'er on LI, what is it you want to install, stone or the porcelain tile?

What size joists, spacing and unsupported span of them do you have where this tile or stone is going?

this is in the future (sometime next year?).... so we haven't given it much thought yet. Ideally, if there were no limitations, we would install 24" granite, but porcelain is also a possibility. I merely chimed in becuase I am clueless as to the limitations of tile floors on a 2nd floor of a wood home.

what are generally the requirements for joists, spacing, and subflooring for larger tile floors? is it rather difficult and complicated? If it is, I'll bypass aesthetics and go with good ol' 12" tiles or even smaller. It's simply not worth jumping through hoops to us...

thanks

ccarlisle · 11-04-2009, 08:43 AM

Well, what you need to do a granite floor depends on what you already have - but I can almost say with 100% certainty that you'll need to strip the floor back down to the joists and rebuild it. That's only because most houses aren't structurally built to take the weight of granite tiles.

The result of NOT doing this is cracked grout or worse cracked tiles due to bouncing floors.

diy'er on LI · 11-04-2009, 01:58 PM

yikes.... scrap the granite idea then. so porcelain is lighter and requires less subflooring work?

right now we're so winded from working and taking care of a baby while redoing our downstairs 1/2 bath that peel-and-stick vinyl is starting to look better and better to me

ccarlisle · 11-04-2009, 03:43 PM

OK, this has gone way farther than the original poster wanted it to go but it has opened up a ton of questions and answers...someone asked me what I meant by "L/720"...these ratios are deflection limits or measures of stiffness.

"L/360" is typically the maximum allowable deflection for a floor under maximum design load allowed by building code, where "L" is the span length in inches. For example, to meet L/360, a 10 ft floor joist can bend a maximum of 1/3" under its max design load (10' x 12" = 120" / 360 = 1/3"). So, to meet "L/720", that same joist can only bend 1/6" (120"/720=1/6").

Basically a floor designed to "L/720" is twice as stiff as a floor designed to L/360. And to meet one or the other depends on what you already have and may or may not require stiffer joists and/or another layer of plywood to meet the maximum alllowable deflection. There's more to it but that's it in a nutshell...

R&D Tile · 11-04-2009, 08:40 PM

Adding plywood doesn't strengthen the floor as far as the joist system, it only adds strength to the flex between the joists.

Two layers of wood are better than one, then a CBU or membrane of choice.

You NEED two layers of wood if stone is used, one layer of 3/4" ply for ceramic, which is bare minimum.

Best to come back when you decide what you want to install.

diy'er on LI · 11-05-2009, 03:00 PM

thanks so much for the info. I'm definitely keeping this in mind for the future. (Sorry to the original poster for unintentionally hijacking the thead!

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