Hey Tom, that’s a great thing you’re doing for world vision, it’s also my charity of choice.
Tom I’m installing 12″ by 12″ by 3/8 travertine on my shower and bathroom floor. I’d like to have the thinnest grout line possible which I think you stated is 1/8″. When would I use sanded or unsanded grout for this application? On my shower walls I’m installing the same size tiles but I’m not sure wether they’re going to be the honed travertine as on my floor or polished marble but my same question applies about which grout to use on the walls with 1/8″ spacing.
Grout joints that are larger than 1/8″ should be filled with sanded grout. That being said, many professionals would say that 1/8″ joint should be receive sanded grout because the grout will want to sag or slump when the joint is much wider than the cement compound. Likewise, joints that are tighter than 1/8″ should be grout with non-sanded grout because the sand is just to bulky to allow enough cement coverage around the sand particles and still bond with the edge of the tile.
That being said, I am glad that you mentioned that might put polished tiles on the floor. It is your home and you can do want you want and contrary to what I said above, I would do the following in my own home.
Install sanded grout in the 1/8″ joints for honed wall tile. For hone floor tile, do the same for consistency. However, if the floor tile is polished, sanded grout really does not look so good so you can use non-sanded grout and do the following.
For 1/8″ grout joint on polished floor tile, you can use non-sanded grout but you need to be concerned with sagging. Joint larger than 1/8″ you would also need to be concerned with cracking. To combat both of these, you need to push the grout deep in the joint with a standard grout float. This will take some extra work and be a little slower. Let it dry a little more than normal before using a damp grout float to scrape and wipe the excess grout off. When doing the final circular grout clean, do not use to much water – just a damp sponge. Too much water will cause the grout to sag into the joint. Lastly, when you are all done (after about 2 hours) you can re-grout any areas that sagged (if any).
This really is not as complicated as I might have described it to be and it is definitely worth it for polished floor tiles.
Best wishes and thank you for supporting the Rock Blog’s World Vision kids!