I am trying to apply a 2nd layer over the original plaster wall in order to sound proof a room. I was going to use 5/8" Quiet Rock. My concern is how to remove the window trim. Also, if I put a 2nd layer of Quiet Rock over the original plaster will I have to do anything different with the trim to make sure it still fits around the window? Will the added layer create too much distance between window & trim?
You are correct in thinking that you will have to make an adjustment to accommodate the new wall thickness. The existing window jambs and any door jambs are set up for the original wall thickness. You will be adding 5/8" to your wall thickness, so you will have to add 5/8" to the jambs. You will have to rip down like a 1 x 6 piece of wood to strips that are 5/8" thick. You should add 1/16" to allow you to sand the exposed edge smooth. Attach these strips to the jambs and they should be flush with the new drywall and then you're ready to reset your trim. It's that easy.