When Should I Use Sanded Grout as Opposed to Non-Sanded?

1/2" is the biggest joint you can use and you MUST use a sanded grout. Unsanded will shrink, crack and not hold up in a joint that size. Also the body hardness of most all 12" tiles require a sanded grout. This has to deal with water absorption .

Any questions you can e mail me through my avatar and check my qualifications there. Any one saying an unsanded grout has no idea what their talking about.. GL

You have the proper grout with the sanded. I do however suggest going with a smaller grout joint. The bigger the grout joint, the more it takes away from the tile. My guess is with 12x12 tiles, y ou are trying to avoid a small cut row. If that is the case, consider going 13x13.

I use sanded grout for floor tiles, non-sanded for counter tops and bathrooms.

1/2 inch is a big gap for unsanded grout, I would use an epoxy grout like Spectra Lock, it as good as u can use being epoxy makes it pretty much bullet proof...

Non-sanded will give a smoother finish but be sure to seal it