Author Topic: condo conversion need to have STC 50 with wood lath and plaster wall  (Read 2476 times)


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I have a  1920's Mediterranean/stucco 3-unit building (1 full floor unit on first floor and 2 smaller units on the second floor).  Walls are original - 2x4 with wood lath and plaster and no insulation (does anyone know the STC rating for 7/8 inch wood lath and plaster?).  Ceiling between floors is 2x10's with 3/4"+ subfloor and traditional oak hardwood floor on top.   There was a fire in the lower unit and it is now completely gutted down to studs on all walls and ceilings.  Upper units had some smoke damage and will be renovated.  As part of the process, I would like to convert the units to condominiums.  Oakland requires all walls and ceiling separating units from each other and (and separating units from common spaces) to be STC 50 (45 if field tested) and 1-hour fire rated.  Have never had noise complaints between units.  For lower unit,  it is pretty flexible since it is all down to stud, but almost no shared walls just shared ceiling/floor (joists) which is also open.  For the upper units and common hallway, however, the walls and ceilings are mostly still in place. Ideally, I would like to see if there is a way to achieve the sound and fire  required ratings without having to open up/tear out existing lath and plaster.  Any guidance/recommendations would be very much appreciated (I will need to be able to document how I reach STC 50 with the City) .  For ceiling/floor separation between 1st and 2nd floor, I had planned on using insulation batts and a resilient channel/clips with 5/8" type x sheetrock.  For upper floor existing party walls, I had hoped I could use resilient channel OVER the existing wood lath/plaster (or perhaps green glue)  with 5/8 x rock without having to removed the existing (or alternatively furr/build something on one side of the shared wall...). Don't have a lot of money so looking for a low cost solution.