Hi, Thanks for the reply. Had I known limestone was such a nightmare I never would have chosen it but the bathroom designer said it was fine as long as sealed properly. With regards to the installation/construction the only thing I can tell you us that it involved a wooden frame on a concrete (old concrete) floor, they used some sort of waterproof boards and a paint on blue rubberised/waterproofing membrane. The tiles are sealed with Lithofin. The pitch of the floor is good, ie all the water drains to the centre well. Husband thinks we should just let it dry out and then seal all the grout lines and the broken tile with silicone. The installers are confident that the waterproofing underneath is tight but surely can't be good to gave water sitting under the tiles all the time? Installers on holiday until 16th - have already emailed them with photos. I guess my questions are: 1) Is it actually doing any harm - ie could we carry on as is? 2) Would the drying out and siliconing work? Currently only the changes of plane and the axis radiating out from the drain are siliconed - the rest is normal grout (which has cracked). 3) Would it gave been better NOT to seal the tiles at all (so water could dry out through them)? 4) If the installers were to rip up the floor and replace how horrific would this be? Would all he wall tiles be wrecked too? Could the glass shower frame be removed without too much damage? I am pretty sure they said ripping up the floor would break the waterproofing. 5) Should we re-tile the floor with something other than limestone, eg marble or ceramic mosaic? I can't tell you how much I wish I had chosen another material. :-(

She was right in that you need to wait a while after installation to know if the mottling will even itself out. Normally after about a week or two, it's as evened out as it's going to get. As for what could cause it, that could be one of a million different things, from jobsite conditions to installer error, to material defect. You can bet a year's salary on it if you were to get reps down to look at it, the blame would be placed on the installer. As for what you can do to rectify the problem, you have one of two choices. First, you can score out all the grout and have her regrout it. The other alternative would be to use a grout colorant on it. The one I recommend is a one part epoxy coating that not only will give you a nice uniform color, but it'll also permanently seal the grout, and make it much tougher for any kind of dirt to stick or stain the grout. Here's a link to where you can buy it on line: Here is a link that might be useful: Aquamix Grout Colorants

It’s three days since it was grouted. And im somewhat familiar with effloressence — I’ve had it on other tile jobs, but that usually can be scratched off or scraped off at least partially and this does not. What i had understood about colored grout is that there is x-amount of colorant within a box and you can definitely dilute out your colorant within the powder if it’s not mixed properly... which is why there is specific mixing “recipe” on the box. If you just wing it On the amount of water added, you’re going to get different concentrations of colorant in each batch....

I'm really sorry for your trouble. Unfortunately fixing any grout issue is time consuming. Today's commonly available grouts (Custom Polyblend, Mapei Keracolor, TEC AccuColor are actually really good quality products. It is not the grout's fault, it is bad application practice. You might be able to clean off the efflorescence with an acid wash. I'd try using Miracle's Heavy-Duty Acidic Cleaner. If you choose to do so, please carefully read their instructions and follow them. Always wear protective gear. You can definitely try to regrout, but if you just fix the bad spots they will stick out like a sore thumb. Color and texture will not match and you will see the patches. It would make sense to plan on redoing the entire area. I hope it is not too large. If it has been grouted recently and if the grout has been overwatered you might get lucky and it cleans out relatively easily. Either way the old grout will have to come out, the more the better. (Not too much if there is a floor heat system under the tiles.) If you're not comfortable using power tools (that can easily do more damage than good) a utility knife will do. Hold the knife with both hands. Do small sections at a time. Start from the middle of the grout line, as you get deeper, work your way out to the edges. When you get to the tile edge keep the blade at a 90° angle, scrape slowly and very carefully because those edges will chip easily. Always scrape away (direction) from the tile corners as those are the most sensitive. It is a good idea to vacuum regularly so you always have a clear view of the "work area". Once the grout line is clean you can grout. I hope you can find out the brand and the color of the original grout (it should be easy if you picked it). Just like with the acid, grouts have instructions too. Each brand has its own unique mixing ratio. Calculate how many fluid ounces of water they specify per one lb. of powder. If you do a small section only a 1 lb. mix should be plenty. A kitchen scale and a precise measuring cup are needed. Always follow the mixing, wait and 2nd mix times. Once the grout is in, wait for it to firm up, in your case (small area) you can you can wait longer than specified. While waiting, you can clean off the excess grout of the tiles without touching the grout line. Once the grout is firm enough (poke it with the tip of the utility knife's blade to determine) wipe it off very-very gently with an almost dry sponge. It helps to cut the sponge in half, it makes it easier to wring it out. Wiping also gives the grout surface's final texture, so make sure it is nice and smooth. If it doesn't work out the first time and the joints are still not completely filled, scrape it out and start again until you get it right. As I said it is tedious... Good luck!