We plan on very tiny joints. Are spacers used for very thin grout lines? Yes. Usually they're small tapered spacers called "marble wedges", as seen in the pic below. but Bill Vincent recommended siliconized latex caulk in another thread. Are there particular brands that perform well? Whatever the brand grout you used, that's the brand of caulking you get, as well, and from the same place, and in the same color as the grout. Just about all grout manufacturers now make their caulkings with antimicrobial agents in them to put a stop to mold and mildew. Do we fill the tub with water before caulking? If it's cast enamel, it's not necessary. If it's plastic or fiberglass, you'd do alot better to make sure the installer supports the "belly" of the tub with mortar or foam. It'll go alot further than filling the tub. The reason for filling the tub is so that excessive movement won't stretch the caulking past its limits. Even a better idea is to limit said movement (which is what you do by supporting the bottom of the tub). Also, I remember a thread mentioning using caulk instead of grout in the "corners," but I am not sure if that means just the bottom corners, or the whole vertical seams where the back and side walls of tile meet. Any place where one wall meets another, or a wall meets a floor (or in this case the tub), it should be caulked.

You will find it nearly impossible to drive the caulk into the joints uniformly enough to look good.

Amen, Glenn. I started when I was 12 helping Dad on weekends and evenings when Mom worked. At 15, I helped during evening weekends, and summer vacations (and getting paid!) when he went out on his own. At 17, I went to the Armstong School of Resilient Installation to learn all that I could, which was before certifications. They confirmed shool completions back then but didnt "certify" as they do now. All my life I have been taught on the job and Dad pulled me aside when other co-workers and his bosses did things inappropriately to save time and cut corners, telling me this isnt the way you should do this, but we do what we have to when we work for someone else. Every facet from pattern scribing inlaid resilient sheet in a room full of pipes and old radiators, all the way down to professionally and expertly installing vinyl/rubber cover base corners. Nothing was too big or too small to do right. At 21, me and Dad had a falling out in business. He had his own busienss now doign commercial and residential subcontract work and was becomming like so many others we laughed at and despised for doing shoddy work to make a buck, then I went out on my own. I am not maligning my Father. I love Him and he taught me pretty much evrything I know, but I couldnt do the work he was asking me to do anylonger when I knew it wasnt right. He had changed. Business had changed him. Money and time was becomming more important that job quality. Business certainly isnt easy, but a time comes when it's either right or its wrong, with little middle ground. Whhen professionals hit that crossroad, then take the wrong path, it changes them, and each time they elect that improper path, it makes the next crossroads easier and easier to take the wrong path, until the day comes that money and time means more than giving people who trust use with their work a professional job. I am an advocate of installer and buiness educataion no matter how they go about obtaining it, whether that be on the job, through a mentorship, union apprentiship, manufacturer or distributor training session, or certification. If certifications are the only way they can get proper training, they shoud go get it. Consumers need to step up and make a fuss when anything isnt exactly how they want it to be. We live in a low cost wallmart and home depot world, where as long as the price is right, they can live with almost anything. As an employer, I instill in my men and women the same installation and customer service values my Dad originally instilled in me, and I demand that on every job. I believe much of the talent has moved to the commercial spectrum too. Its where the money is at. Interesting you should say that (about commercial work getting the good men). When I left Dad, I went all commercial for about 10-11 years before we started opening up stores. Did alot of traveling and made alot of money. Now we bring those values and quality to the residential sector. In the end if something isnt done right, it doesnt matter why.

Any change in plane is to be caulk not grout. Grout will not move with the walls expansion/movement, it will crack. TCNA standards are caulk,