Hi there - we are considering putting 24" x 24" tile in our kitchen. A friend has her entire main floor done in 24x24 tile - three years later no problems with cracking. I think it is correct to say that properly installed it shouldn't be more prone to cracking. That said, I have been told that properly installing large tiles is technically more difficult, so be sure to get an installer with good references for installing large tile.

24' by 24' - that would be some big bathroom!

It's not your typing. For some reason, when typing in a thread subject, the software for the website will always change it from quote marks to an apostrophe.

As for the 20x20, it all depends on how solid your floor is. If it's marginal, the size of the tile COULD make a difference. But so long as your joisting and subfloor is strong, you should be okay. There IS a movement going right now in the industry to institute a new stronger deflection standard for large format tiles, though (anything over 16") just because of this.

Thanks for the quick responses.

Bill, I think you've hit on what I'm worried about - movement of the underlying structure. Interesting that the industry is thinking about addressing deflection standards for large tiles.

Sooo, I guess I need to get our contractor to check out the joisting and subfloor. Or maybe I should just pick out some smaller tile for peace of mind.....

Sigh. The 20x20 tile is the first budget-friendly item I have fallen in love with.

we have 20+ yr old home and are laying tile in two baths on concrete slab first floor and a bar and half bath on second floor with a plywood base...
my tile guy says that where floors could be uneven and the tile is larger to avoid having tiles crack from uneven levels of the subfloor..he adds extra mortar base to float the tile more...
it is not that larger tiles in the same area would weigh more than the same dimension of smaller tiles--it is about the levelness of the surface under them to large extent--

the large the tile--the larger the area it covers that must be level...walking on tiles where there is an unlevel base puts stress on them--doing it enough will eventually crack them...
it is certainly possible for smaller tiles to crack if installed improperly and even if they are installed correctly and there is enough foundation shifting, they could crack...but my guy was worried more about the levelness of the floors...when you are meeting thresholds in different rooms that can be a problem...especially if they are different materials...

it is not that larger tiles in the same area would weigh more than the same dimension of smaller tiles--it is about the levelness of the surface under them to large extent--

Although you're right-- the floor does need to be incredibly flat when using large format tile, the big consideration is the strength of the joisting and subfloor. Yes, static load, which is what you speak of with the weight of the tile, is important, but so is what's called live load, or things in movement across the floor, which cause the floor to bend back and forth. All woodframe floors have some amount of deflection to them. The more the deflection the less chance there is of a hard surface such as tile surviving. Now you bring in large format tile that as you say, covers so much more area, and now the deflection standard is even more important, because it would take less deflection to affect each specific tile. THIS is the main consideration when deciding to use large format tile or not. Once it's determined that the floor is strong enough for it, then you can move on to the flatness of the floor.

I guess our joists are not a problem them--contractor did not mention that as factor when we talked about whether or not to use the 20x20 vs the 13x13--

would a small half-bath(without any natural light)that is basically 4x3 almost be too small for 20x20--no pedestal sink--staying with the original vanity which is med stain oak..

We have 24x12 tiles in the bathroom and kitchen. They look great, though they are only a year old. Would those be more stable?
They also were a lot less expensive than the larger ones.

Depends. Do they run with, or across the joists?

would a small half-bath(without any natural light)that is basically 4x3 almost be too small for 20x20

Not at all.

Bill, if you're still out there ...

Am I correct to assume that a 20 x 20 tile would have the same deflection as a 20 x 12 tile?

Also, is a thicker tile less prone to cracking (all other things being equal)?

Bill, thank you so very much for sharing your time and knowledge. Have you ever thought of teaching? Your example really helped me undertand the issue. Now I remember the reason I avoided the engineering classes in college.....

Unfortunately, I can't get to the joists and floor "innards" just yet. The renovation isn't scheduled to start for another week or so.

Even though I think I'm probably obsessing over this issue more than I should I am going to bring it up with our contractor to get his thoughts. He put the original addition on the house back in the 80's so perhaps he has some insight into why that original tile cracked.

This renovation stuff is never easy. Probably why I've put it off for so long.

Have you ever thought of teaching?

I do, every day, both in here, as well as on the job. :-) I've had an apprentice with me constantly since 1999-- only the one I've had for the last 4 years was my own stepson. He's about ready to become my full partner, though, so it's about time to find someone else interested in learning the trade!

Bill, would a floor with a deflection of L/480 be sufficiently stiff enough for a large format tile?

Yes, it would.

Let me add a caveat to that-- that's provided you have a minimum of 3/4" of subfloor before cement board or Ditra if the joisting is 16" OC, or 1 1/4" of subfloor if it's 19.2" OC or greater.

Thanks, Bill. I don't know the joist measurements yet, although I do know we're using open web trusses, but I'll keep your guidelines in mind before picking tile!

If you have trusses engineered to give you a deflection rating of L/480, you're fine, again, so long as the subfloor meets the requirements I described above.

Hi, Bill I was not sure if I should start new thread or not since its same subject/ similar situation, I want to use a white glass over porcelain tile it is a very strong thick tile that is 24 x 24. (have you seen it/use it before?) I have wood truss (2nd floor) framing with varying spaces from 16" to 24". Probably only the shower area they ran them closer the rest of the room is 24 We have 2 layers of 3/4" plywood down and we are going to run screws every 4-6 inches or so to reduce movement. I was then planning to use the orange ditra with the little squares to eliminate the possibility of cracking. Am I correct? Old floor was 6 x 6 bathroom ceramic wall tile and it was a mess with cracks. I don't want a repeat performance. I thank you in advance for your help.

That should be fine.

Thanks Bill!