If: You were going to use stone tiles, and the original joists were notched deeply for plumbing, and you had no obstacles (wires, pipes, etc.) in the way; Then: You could sister the joists with new stock of the same size, doubling the built strength and resistance to deflection. The subfloor and underlayment must be up to the task based on what the finish is. Large-format stone needs the greatest amount of support, small mosaics need the least (in the tile family), and vinyl needs no support at all beyond what springiness underfoot you are willing to live with. Create your own (tile) reality here. If you are satisfied that you need no structural enhancements beyond the original construction, you can sister with 2x4's or 6/4 stock screwed/glued to the sides of the joists. Select very straight stock for this and run string lines across the ends to set them evenly. If you are making up for 6" of mortar now removed, you may need to raise the level considerably to meet your Vitrolite walls (unless you're adding a baseboard tile to cover the gap?) so plan the heights out really well considering what you will use as finish. To get the floor back up to the previous height, sistering may call for 2x6's (or more) to achieve the needed height. I'd probably use two layers of plywood and Kerdi membrane for a tile floor; assuming 24" centers on your old framing. If 16" centers and very stout joists (I've seen 3x12's used in old houses) then one layer of 3/4" plywood is fine, plus the Kerdi. Search the "Bathrooms" forum for full discussions and how-to's on Kerdi and it's sister product Ditra. Casey

thanks to all who have posted so far, especially Eric. We can probably save/budget down the road for a kitchen redo, or do part of it ourselves. Additions would be a little harder for us except finish work (floors, tile, etc. Can do drywall even but would need to find time to do it). What that kitchen has is a U shaped layout, not too bad except there are overhanging cabinets between a small dining/family space and the kitchen. It's a counter/pass through kind of setup where someone can sit at stools and talk with the person in the kitchen....except the cabinets hang down so the person in the kitchen has to look under them. We would likely tear those out and relocate the stovetop to the perimeter wall and make that pass through an island. Then that entire space could become kitchen/dining. It is possible we could still move out a wall on that (kitchen) side of the house down the road too, we are in Hawaii so all the construction costs are much, much higher than mainland. So jealous of all the posters here who can put on a large extension for less than 50K. Plan A or Plan B will cost us about the same. We don't plan to sell and move anytime soon, but should we need to we're leaning toward sq. footage instead of just extending current bath and upgrading the kitchen. Our neighborhood is about 20 years old so people are beginning to redo those rooms as the fixtures and appliances are ageing. We redid all the appliances about three years ago with stainless finishes, new faucet/sink, and redid the countertop Corian, so the kitchen is livable - just need to clear out some clutter and make smarter usage on available storage space. We could paint or restain the cabinet doors to freshen it up. A few neighbors are creating the "big bang" kitchen now but I'm not certain a 70K upgrade will improve the value that much as a new neighborhood is planned about 5 miles away within the next couple of years. Would we love to live in a "WOW" kitchen, of course. But as with most people we have to make a decision on where it is best to spend the money for now. We could feasibly also add on a 2nd story in future years, but we prefer the single story and if we age-in-place as planned, the new bath will include wide accesses and no-curb shower.

How would you fix the subfloor? That's what I was planning to use the wire mesh to do. We're talking pretty small holes in areas where there won't be any foot traffic (behind the toilet and vanity). I wouldn't be able to get any wood or other solid surfaces in there. The biggest hole is about the size of two fists.

You mean waterproofing PRIOR to installation of tile as well as during/after install? Yes, you have to build and waterproof the shower before a single tile is installed. Tile and grout are not waterproof, they are just the part that you see. Not a pro here, but to educate myself (after a shower disaster, and in order to make a better hiring decision when searching for new pro to fix bathroom), I read the shower chapters of the TCNA handbook, read waterproofing threads on this forum and the John Bridge forum, and checked out DIY books from the library. I wasn't intending to DIY, but it was very helpful to learn what building a waterproof shower really requires. There's a lot of bad info out there, so don't go digging around in YouTube videos, with one exception - I watched Sal DiBlasi's videos. I think he has another site with more info on it, but I haven't gone on there lately. Doing some research before talking to contractors will help you make a better hiring decision. You can order a downloadable version of the handbook for less than $40: https://www.tcnatile.com/products-and-services/publications/218-english-publications/188-handbook.html You can search for Sal's videos online: Sal DiBlasi, Elite-tile Company, in the Boston North Shore area. After you educate yourself, start interviewing contractors (not sure if you want a GC or if you are going to directly interview tile professionals). Ask this question: "How do you build a shower?" For your entertainment here is a story that illustates how hard it can be to find an excellent tile pro, and how vulnerable people are to GCs' hiring decisions regarding subs. When you do find an experienced and qualified tile pro, understand that on average a correctly built and waterproofed shower will be several thousands of dollars. Don't skimp on this by hiring an unqualified person. The chances of a leaky shower is far too great a risk. https://www.gardenweb.com/discussions/5725013/what-to-do-when-a-project-goes-completely-south#n=28 In my case, I hired a very expensive GC, who then hired a very cheap and unqualified tile installer. If you hire a GC, you need to find a way to ensure that he/she doesn't cheap out on the tile pro to increase their profit. I haven't found a way to do that yet. The only 2 projects where I had to hire a GC, they did this and it caused big problems. So, if you hire a GC, have an honest talk with them about who they are going to hire to build your shower. The tile pro is the most important sub that will be involved in your bathroom reno. The tile pro is the one who is in charge of building the whole shower. Sometimes a framer will frame the shower, but the tile po is ultimately responsible for the whole thing. Don't let a GC just tell you the person is qualified; you need to see that tile pro's prior work and ask them the question "How do you build a shower?" and here his answer for yourself.