I have two questions regarding my 7 year old tiled shower enclosure with mosaic tile floor that has some cracked grout which needs to be repaired. First, I purchased pre-mixed grout which instructed to clean the existing grout using their sulfamic acid cleaner when "rejunaviting old grout". [url]http://www.custombuildingproducts.com/products/grout-materials/pre-mixed/simplegrout-pre-mixed-grout.aspx[/url] I cleaned the floor twice with the sulfamic acid, first pass was 6oz diluted in 1 gallon of hot tap water which I scrubbed using a nylon bristle brush then rinsed with cold water. Later that day I diluted 11oz with enough hot tap water to cover the entire floor and let it soak for 30 minutes before rinsing. [url]http://www.custombuildingproducts.com/products/care-maintenance/cleaners/tilelab/tilelab-sulfamic-acid-cleaner.aspx#[/url] After some additional reading online it sounds like the sulfamic acid might have done more harm than good, and now I'm wondering if I now need to regrout the entire shower floor. Could doing this have compromised the existing grout? Or do I now just have very clean grout that is ready for the repair? Secondly, after we purchased the house the builder had to replace some of the mosaic tiles that were cracked. I noticed they grouted the gap between the floor tiles and wall tiles, then ran a bead of clear silicone on top of the grout. Is this common practice or should that gap have been filled with one or the other, but not both? If I am repairing the cracked grout should I also cut out the grout between the floor and walks and replace it with silicone!? I read that silicone is the better choice over grout for "changes in direction" like floor to wall. Any advice would be very much appreciated, thank you!

I'm in the process of installing a new shower using permabase ultra as the underlayment for the tile. Is there any way to get rid of the odor from the permabase? It's a very strong smell and makes it hard to breath at times. It might be a few weeks until I can get the tile up (assuming that will stop the odor). I had the thought of skimming over the permabase with a mortar or thinset to help trap in the odor. Has anyone had to deal with this before?