Hey all. I have a typical 1930's Marina Style home in San Francisco. A lot of these homes featured a fire place with built in bookcases/cabinets flanking the fireplace. The bookcases are offset about 2" from the rear wall. I wanted to create a recess on the bottom portion to fit A/V equipment so I removed the bookcase backer on on side. I expected to see the studs and exterior, tar papered wall, but found a thin layer of what looks to be plasterboard. It's not supported by lathe, just a thin layer. I drilled a tiny hole to see if I came in contact with anything behind it and it went straight through. It looks to be about 1/4" thick. This is the only wall that appears to be constructed this way. The surrounding walls are 3/4 ply on the bottom about 1/5' up, then lathe and plaster. I'd like to attach a 1/8th" ply board to it to complete the recess. I plan on using construction adhesive, but need to anchor it somehow to get a good purchase between the wall/adhesive/board. I'm worried I might crack the plaster. So couple questions: [LIST] [*]What type of anchor would you recommend considering the plaster seems delicate? [*] [*]Is this plasterboard? Was it used this early? Does it have to do with heat insulation or protection near the fireplace? [*] [*]Is it safe to anchor something to? [/LIST] [I]TL;DR- I have a 1930's home with a two bookcases that flank a fireplace. The cases are offset from the wall about 2". I removed the back of one case to create a recess and found a thing layer of plaster (no lathe). Is it safe to anchor 1/8" plywood to and what's the best way?[/I] Thanks in advance.

When I bought this house six years ago, there was some flaking ceiling and waviness to the plaster walls around the chimney. The realtor told us that when they replaced the roof, they didn't seal properly around the chimney, but it had been fixed. I have every reason to believe this is true because in six years I've never noticed any moisture and the attic insulation has remained dry. The problem is that the wall on all four sides of the chimney has continued to deteriorate. On two sides, there are pockets of powder behind the wallpaper and one section has split completely open, with a big pile of powder at the bottom of the tear. On the other side, the bathroom, the painted plaster has flaked and dropped powder, the walls are bowed under the tile and a couple outside the tub have fallen off. Now we're getting ready to sell, so I have to do something with the mess. I called a contractor and he told me that he couldn't remember what it's called... he thought "phosphate"... and that once the wall had been damaged, whatever it was continued to grow and that we'd need to take off the tile and treat the wall with some kind of spray that would kill the "phosphate" and it wouldn't be cheap. I don't think he really wanted the job because he said that he'd get me an estimate in a couple of weeks, suggested that I sell "as-is", didn't take any measurements and he didn't jump on my suggestion of replacing the tub tile with a surround as being significantly less expensive because he said the wall would still need to be treated. Again, I don't think he wanted the job which brings me to one of the web's most helpful sites. Could someone give me an indication of what he was talking about? I've searched the forum, but I'm not finding an answer. Also, is there some reason we can't just rip out the plaster and replace it with a tub surround on cement board? I had asked the contractor to provide me with options, but he was only here a few minutes and it really seemed like he didn't want the gig. I'm fine with doing the demolition and cement board myself, but before I start tearing it apart, I'd like to know what y'all have to say. BTW: Quite possibly, the plaster is from the 40s and the roof may have been done ten years ago. Thanks.