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Insulation Behind New Bathroom Walls

3443 Views 8 Replies 6 Participants Last post by  Wiscbldr
House was built in the 30's, in CT. We are taking down the original tile in the alcove where the bathtub/shower is and putting in a plastic tub surround. The original walls are plaster and lathe. The original tile only goes part way up the wall, and the walls above the tile are cracking. Sand is falling down into the tub. The tub is the original cast iron.

When we took the tile and plaster and lathe off the back wall of the tub, which is an outside wall, there was nothing but the studs and then the outside boards of the house. There is also a gap of about an inch between the studs and the tub now, due to the width of the old plaster and lathe and tile.

I'm looking for suggestions of how to finish that outside wall so we can have some insulation and get the wallboard out far enough to attach the tub surround. Should we just put in fiberglass batting and build the studs out with firring strips to put up green board? Does anyone have a better idea?

Thanks for your help!
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No fiberglass batts. Get rock wool. FG batts suck, for several reasons. Use cement board around tubs, and waterproof it. No poly vapor barrier, either.
Seal up any cracks and penetrations in the outside wall. The fiberglass batts in the bays use unfaced and cover over with foil faced iso board it comes in different thicknesses so you should be able to get something close to what you need and tape all the joints with metal tape. If you are just going to paint use green board if you are using tile get cement board
Gary: It is my understanding that anything near water should be cement board, and the green board is not what is was originally cranked up to be. Regular old drywall is OK behind a shower stall? I would have guessed the humidity may be a problem, if not a tiny leak, and that cement board is the safest bet. No?
jklingel, my bath reno has been done for over a year. We went with Greenboard on all walls, put up a 5 piece surround, and have not had any problems. We have had no problems with ours.
Vapor barriers in bathrooms are a debatable issue as far as I am concerned. Excess moisture in bathrooms should be evacuated by the fan which should be on either a timer or a humidistat.
"Regular drywall is fine behind the plastic shower surround....." ------- many of these surrounds are five piece and 1/8" and thicker, a vapor/water impermeable barrier. All the ones I've installed, and don't paint the drywall or the adhesive won't stick. Silly to run the v.b. when used, below the tub- as I hope it's water-proof..... Won't even mention the giant hole around the drain/waste and overflow to the damp crawlspace....... On a tiled wet wall another story....

Im not a contractor or an expert on insulation, tiles, etc.. but, I happened to see a Holmes on Holmes show last night and they were removing some old tiles and insulation. Their big concern, and perhaps yours given the age of your house, was the possibility of asbestos and vermiculite. Google both and consider having your area tested just in case. Good luck....
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