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slatergrl 02-28-2008 06:28 PM

What are the joist requirements for a tile floor?
I've done some reading and question asking on this site and understand the basic subfloor requirements for tile, but what are the joist requirements? joist size, spacing, span? A friend of mine wants to add tile to an old farmhouse that is post and beam construction. It also currently has "farmhouse" wood plank floor boards as it's only floor! Can tile be installed over this type of floor, if plywood and cement board is added? Thanks:)

Rehabber 02-28-2008 06:48 PM

Need to know the joist size, spacing and span, so the amount of deflection or flex can be calculated. And you will still need to add plywood and backerboard or Ditra

Bill_Vincent 02-28-2008 07:41 PM

Slatergirl, I assume these are 4"x8" beams 48" on center?

nacko 02-28-2008 07:46 PM

if the floor flexes more than 1/8" in 10' then it probably needs beefing up (tile/joints will crack). that's just rule of thumb from memory, you can look up the actual allowable deflection in the building code books, its usually something like 1/360 of the span for members that generally span 14' or so.(when I say beefing up, I mean sturdier joists or smaller spacing)

Bill_Vincent 02-28-2008 07:54 PM

The only time that L/360 is going to come at 14' is with 2x10's. You're all missing that she said in her post-- this is post and beam. All the deflection tables go right out the window.

Let her answer my question, and then we'll see what we can do.

slatergrl 02-29-2008 07:03 PM

My apologies, I posed this question without being fully prepared with all the info on my end. I'm trying to find out what size the joists are(not my house) and I will get back to you. thanks again

Bill_Vincent 02-29-2008 07:09 PM

Not a problem. If you could also find out how thick the planking is, that'd be great.

Bud Cline 02-29-2008 11:47 PM

.....and varify the beam spacing.:)

javan 07-16-2008 10:08 AM

And send us pics!

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