We had new ceramic tiles put in the shower. The tiles are large size (12x12) and the grout line is about the width of a pencil. After a few days we noticed very thin (hairline) cracks in the grout, especially around the shower bench and the corners of the shower. The tiles are all in place. I think the contractors mixed the grout too thin. Can I just sand those areas of grout down a bit and then put new grout on top of it over those areas?
Call the contractors back out and have them fix it. Yes, it sounds like they mixed the grout incorrectly. The tiles also shouldn't be that close together. When they set the tiles, they should have placed little plastic plus-sign-shaped spacers between all the tiles. This ensures a uniform and correct-sized grout line (about 1/4 inch for wall tiles) between all of the tiles. Seems like this tiler didn't know what he was doing. If you do try to fix it yourself, get a grout knife in the tile section of a home improvement store. This has a serrated edge to it that you use to actually grind into the grout (although it may not fit if the tiles are too close together). After you've ground out most of the grout, mix and apply a new grout. Also, look for grout that actually stays a bit flexible after it sets (I don't remember what it's called). It's good for wet areas like a shower and less susceptible to cracking.
The contractor did not use the correct underlayment for the tiles. This means the floor underneath moves and flexes when weight is applied. Tile and grout are very rigid and don't flex. As for the grout mixture, it does not matter. Too soupy, too hard, it all end ups to be the same, just a matter of clean up for the worker. If they wont repair it, contact your attorney, you hired them to do a professional job, not a slop around side project.
There are many questions to ask first. How old is the building? Is it still settling? If so: wait until it is done moving before repairing, or you will just end up doing it again. Was the tile installed over cement board, plywood, or what? Each has a different effect. Did you use mastic or latex/polymer modified adhesive or..what.. to adhere it? Is this a wet area application (shower, counter top, etc?). This could be as simple as having too much water in the grout when it was mixed, or too wet of a sponge during clean up. If that is the case, you still have to remove it all and redo it. Just fact-find to learn the cause before you repair it, so you only have to do the repair once! Ultimately, if you paid someone else to do the job, have them fix it. If you did it yourself, go to the library and read every tile book you can find. The answers are out there, but it might take some research to find them.
u sand out the grout that is on the wall and regrout it with properly mixed grout, and make sure you caulk it too. ive noticed some people forget to do something like that, and end up with a new shower that now has sunk into the house.
Humm... this could be a couple of problems, the shower bench.... if the cracks are between the vertical tile (bench) to the wall tile... this could be that the contractor did not support the bench correctly... but this is not unusual... Do you heat the shower up with the water hitting the bench and not the wall? This will cause the bench to heat up and if you sit on the bench... it will flex with your weight... again this is not unusual.... the grout is cement... hard/solid... this will not give. The cracks will always appear... if you have the exact color of the grout you may get lucky and be able to purchase a elastomeric caulk which is used for flexible points in tile installations... example of this is normally used for bath tubs to tile installations where you have the expansion and contractions of the iron tubs compared to the tile floors/walls.... Heat from the tub will expand and the tile will not. It should be the responsibility of the contractor to repair the problem but not an unusual problem. If the contractor will not return... you may have the warranty issue. I would remove the grout and install the elastomeric caulk. At the home centers you may decide to get a grout removal tool to dig out the grout or there are power tools with the special bits to do it faster... but they have their own problems with scratching the tile edges... take your time if you do it.... Get the vendor information on the grout and check if they have matching color elastomeric caulk.... the original grout mixing is not the problem.
