What's the danger in using unsanded grout?

[gordon21]

I ordered 1325 SF of floor tile last weekend. It is a 1/4" solid body color porcelain tile that imitates slate. 18"x18" tiles that are blueish gray, irregular top surface and top edges that are almost 90 degrees. I want to lay it with a minimal grout line (1/16")to imitate a real slate installation. The tile store took the order OK. It is going on top of 1.5" of new OSB and the OSB is topped with 1/2" concrete board. The base is extremely stable.

Two days later they call back and say that I have to sign a liability waiver if I intend to do a grout line with unsanded grout. The guy mumbled something about expansion and that unsanded grout was dangerous, thus the waiver. I can't imagine how tile is going to expand and contract enough where the grout composition makes any difference. If anything, it would seem as though the lack of large sand particles would be better.

Please explain the reason why if this guy is telling me a straight story.

 

[SnowRidge]

Sanded grout is stronger. Use of unsanded grout is not recommended for joints over 1/16" according to my books, and may lead to cracking. I used sanded grout and didn't have any trouble with it. Why not just use it, since it is stronger?

 

[ToadHill]

We used unsanded grout on marble floors all the time. As long as the grout lines are less than 1/8 inch it will be no problem.

 

[InlineDieselFan]

What little I know about tile, if the grout line is less than 1/8th inch sanded grout is not needed.

steve

 

[RobJ]

I don't see a probem either. Just be careful when grouting, non sanded seems to dry faster and is harder to get up. I start working the joints and wiping off the excess much quicker than sanded, I also work a smaller area.

good luck,
rob

 

[kennyd]

That salesmen is full of cr**, get the unsanded with joints that small.

 

[gordon21]

Thanks guys. I thought I was correct from the start.

I have put down tile several times before and always thought 1/8" was a reasonable boundary line between sanded and unsanded.