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1898 Sitting Room with Exterior Walls to Bathroom

We want to convert the 6'9" x 8'4" sitting room off of the master bedroom in the 2nd story of our 1898 foursquare to a bathroom. We have all of the plumbing worked out, and have read on the forums that it's best to pull all of our plaster and lathe from the walls and ceilings. While we should be able to reinstall cement board and/or moisture resistant drywall on our ceiling and two interior walls, what do we need to do on the two exterior walls that were plaster directly over brick? Can we install drywall or cement board to the brick without studding them out using screws or glue? Do we have to put up stud walls on the exterior brick? If so, can we use wood smaller than 2x4s? Space is at a premium we don't want to reframe and retrim our 4.5' wide x 7' tall window on the 8'4" wall. The shower will be located in a corner of one exterior and interior wall, tiled floor to ceiling. And we'd like to tile the floor and all walls up to 5' high.

Re: 1898 Sitting Room with Exterior Walls to Bathroom

Keep all of the plaster. Scr-ape off all of the loose paint, etc. You will bet a far better result tiling to the old plaster than to new drywall. Have the electrician keep the holes for the new wiring to a minimum. Pull up all of the old flooring; save the finish floorboards for repairs elsewhere. Do not use cement board. Us a 3/4" layer of CDX (or BCX) plywood, and then a 3'8" layer, then apply Ditra mat and floor tile to that. Thinset does a great job of adhering to old plaster on its own, but you could use a bonding agent if there are areas where the white coat of finish plaster has peeled off.

Re: 1898 Sitting Room with Exterior Walls to Bathroom

Casey - thanks for the suggestions, especially regarding the old floor boards. To make sure I understand what you're saying, put down 3/4" plus a 3/8" layer of plywood for a total of 1-1/8" plywood subfloor? Why the second layer?

Tiling directly over plaster for most of the bathroom makes sense, but will that really work in the shower area? Wouldn't we need something for moisture resistance between the plaster and tile, like Ditra?

Re: 1898 Sitting Room with Exterior Walls to Bathroom

You could also install drywall boards over the existing lathe and build out the door facings to suit? If you use a good quality CE2 grout also along with moisture resistant drywall boards then you won't have any problems.

Re: 1898 Sitting Room with Exterior Walls to Bathroom

Thanks for all of the help guys. Just an update on the project with a few more questions.

For our interior plaster and lathe walls, which have 2"x4" turned 90 degrees from normal we are sistering the studs (with plaster and lathe in between) to give our plumber sufficient depth. Then the plumber will cut out sections of plaster/lathe, giving him ~1.5"+.5" (lathe + plaster) +~1.75" = 3.75" to work with. Any idea whether it's better do install the 2"x4"s as furring strips (without top plate and bottom plate), or construct an actual wall that sits on the existing floorboards (before we cut / pull up the remaining floor)? Our plumber and electrician are pulling permits, so we don't want to inadvertently get in trouble for an improper wall build out.

Image showing studs: https://www.facebook.com/photo.php?fbid=10151379120935266&l=0bf5984741

Image showing room: https://www.facebook.com/photo.php?fbid=10151398897460266&l=691cab4e11

On the exterior wall, we are going to move forward as recommended using the ditra system on the floors, the kerdi system on the shower walls, and tiling directly on the plaster for the 4' tile accent around the rest of the room.

We will be installing a frameless shower surround that will be supported on the door/long side (total 46") with the stud wall. But on the short side, the 33" shower glass must be attached to the wall that has plaster over brick. Advice on the best anchors to use? Our brick is soft enough that tapcons never seem to hold well. Has anyone used the Toggler Alligator anchors successfully? Or should we build out a stud wall in order to ensure a secure glass installation?


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