Floors need removal of baseboards, and/or shoe molding, and of old flooring, usually additional support such as an additional layer of exterior plywood, a layer of ¼” to 1/2” concrete board, and if there were previous leaks new subfloor and joist repair/replacement may be needed. The floor can have no flex whatsoever and must be level. Concrete board will stop the expansion and contraction of wood products but is not a substitute for a solid floor. Always overlay joints in the underlayment with concrete board to stop expansion and contraction of the finished floor. The use of a flexible membrane such as Schluter-Ditra is highly recommended but expensive. The membrane absorbs slight movement in the floor keeping your tile from cracking. At about $2.00 per square foot, including membrane, tape, and additional mortar most people forgo the membrane in favor of strengthening their floors. However, there is no substitute for installing the membrane on concrete floors that have previous cracks or in my opinion concrete floors in general. When concrete cracks it is an indication of stress and these cracks will show up in your tile eventually. While I highly recommend the membrane under all floor and countertop installations the cost at this time keeps it off of my must do list for all but concrete installations. Ceramic base is the best option for waterproofing walls where no wall tile is installed. The more modern look is to use wooden base. Understand that this is not recommended but it is being used more and more. If base is being painted it should be made from a synthetic material. For this type of installation I recommend installing the base ¼” to 3/8” above the ceramic, than caulking the gap and install shoe molding over the caulk for a more finished look. This will keep minor leaks/spills confined to the bathroom but allow the most up to date look in your room. A synthetic material should be used for the shoe molding so it does not grow mold or mildew, nor will it allow water to wick up to the base.

Walls require more attention to detail to prevent leaks and the formation of mold and mildew. The best way to remodel a bathroom is to strip the walls down to the studs and install mold and mildew resistant drywall where ever there will not be tile and cement board wherever tile is to be installed. Understanding that most people are not going to spend the extra money to replace all of the drywall I recommend that all existing drywall be cut at least 1” above all floors, tubs or other areas that hold water. Wet areas must be taken down to the studs and a ½” cement board installed. I recommend this even for tub surrounds; you can’t imagine the number of tub surrounds I’ve removed that had been leaking. Be sure to use cement board seam tape and mortar mix at all joints and corners. Cut any holes you need in the cement board as small as possible. Any damaged studs must be replaced. This is a common problem around the tub/shower faucet where water penetration usually starts. When installing new tile in a tub/shower area it is a good idea to update the faucet at this time. Don’t go cheap here as this is the only time you can replace this faucet without tile or drywall repairs being required. A single lever faucet creates less area for water penetration than a 2-3 handle faucet. If recessed shelves are desired lay them out before installing the cement board and use cement board to cover the studs and the back of the shelf area. Use only screws recommended for the specific cement board you are using, DO NOT USE DRYWALL NAILS OR SCREWS. Always attach the cement board as instructed by the manufacturer. This is very important as these boards are going to hold a lot of weight and need to remain waterproof.

If retiling your bathroom walls and floor this is a good time to think about replacing your tub. Builders usually set your tub on 1/2” to 5/8” plywood or particle board. The most likely place for water to start penetrating to your subfloor is at the edge of the tub. Very seldom have I found a floor joist under the tub edge. If you consider the amount of weight that is exerted on the tub edge every time you sit on the tub, fill the tub, or stand in the tub you can see why this area is extremely vulnerable to leaking and must be kept caulked. When we install a new floor and tub together we always add ½” plywood to the entire floor to help stop flexing at the tub edge. Many times we must cut out the sub floor and replace it in this area because it is either rotted or bowed to the point of being useless.