"floor flex" again

Hello again,

Wow, asking for me personally huh? This time you might receive an invoice. :laughing:

Luckily just about every home I have worked in met the min. building code of L360 deflection which is also the min. spec for ceramic tiles. A few were so bad that I gave my opinion and walked away.

Some people think the truth for proper tile installation is achieved through democracy. If 3 people say it's fine and one says it doesn't meet specs, they're likely to believe the 3 hacks. Pricing is the same. After a failure, when asked about the handyman they hired, they say they did not hire the cheapest. Well ok, but they only searched out people that weren't qualified and therefore all the prices they received were too low, and they got what they paid for.

Your quote;

"baloney,that's not important,I've been doing tile for 30 years and never had a problem"

Click to expand...

is something we hear often here on these forums.

That's why it's best to edumicate people about how it's supposed to be done. A cynical person will dismiss good advice, thinking that he's only trying to charge more and the other guy has been in the business a long time and so he must know what he's doing. Yea right. :whistling2:

Jaz

good to see you're still around "Jaz"

anyway,been meaning to ask about "Ditra". It sure looks like a good product, especiallly compared to the alternative which the manufacturer says is just as good but cheaper. (It doesn't look like it even compares) yes,it IS more expensive than CBU but it seems to be worth it. question: would using "Ditra" on a floor that fails the "flex" calculations by not a whole lot, actually negate the calculation? it sounds like it MIGHT,after all, using "Ditra" actually allows the tile structure to "float" over the substrate and any movement of that substrate wouldn't be transferred to the tile. is this just crazy thinking?

ps: I've still got those 3 bags of special "thinset" that I bought at "Bedrosians" awhile back which is supposed to "negate" the calculations. (to a certain point anyway) maybe using that thinset AND Ditra will "super negate" the calculations.

tnx,

oh yes,Jaz,glad the building department hasn't caught up with you yet, we still need you in this forum.:jester:

Schluter makes no claim that Ditra should be installed over a floor that does not meet standard deflection specs. Ditra helps more by uncoupling the tilework from the substrate, therefore for lateral movement, not deflection.

Ditra costs me a little under 2x the cost of CBU's, but it's easier and much better. If I had to pay retail, I might think twice, well for sure I would.

That super thinset is Reflex by Hydroment, real good stuff but it's modified so use it to install Ditra, not the tiles if you wanna follow Schulter's wishes. I might forego the warranty and use it for the tiles anyway. Just give it an extra day to dry before grouting. The first choice would be to bring the floor structure in compliance though.

Oh yes, the building departments don't much care about how the tilework is done.

Jaz

Ken,

I think your joists rating is about L318, which is risking it for the books. But depending on the condition of the joists, their species and grade and the type of load the floor will receive, it may still be alright. Obviously you should try to stiffen them up if at all possible.

There is no magic that happens with these specs. It's not gonna be guaranteed to work at L360 and better, or fail at L359. These numbers are to guide you to determine where you stand. Plus you've got Reflex mortar.

For the record, the deflection along the joists' length is more forgiving than the deflection between the joists. (subfloor strength). The difference is curvature of the subfloor is greater as the distance is reduced.

I noticed you posted at JB's the other day. Good move too.

Jaz