I have a client who has had some questionable work done on the NEW home she had built. Just weird stuff... like sheetrock butt joints in a ceiling running perpendicular to a joist - NO tape - cracks appeared instantly.. etc... Anyway, now she is not happy with her tile floor. When it was originally installed the installer didn't put enough grout in the cracks. Now there are craters that catch every crumb, dog kibble, etc. she drops on the floor. So, she wants me to add more grout. My concern is that it won't adhere and then will fail prematurely. I've asked a bunch of people (like at Color Tile, Home Depot, Floor Stores, etc...) Most of them said "no problem just add more grout" some say, "sure, just rough up the existing grout with a dremel and then add more with plenty of admix", and a few said "no way, it will fail for sure". So... any more suggestions / recommendatioins? Incidentally, the tile floor was installed after the original morons installed a hardwood floor on a cement slab -- with NO vapor barrier. Strangely, the floor cupped in about a month!