Hi, folks...
I just recently finished hanging an isolated suspended ceiling system in order to wall off my space from my upstairs neighbour's OBJECTIONABLE heels knocking against the floor at all hours! I'm trying to seal off the perimeter of the assembly with mastic... which seems the stuff to use - based on what I've read basically EVERYWHERE. How on EARTH do you get the stuff to jam in?? I've got an approximately .25 in. gap between the edge of the assembly and the adjacent walls. Can anyone help out on this - ? Anyone done it before??

Thanks
Jonathan

Johnathan,

1st - you do not want mastic - you want acoustic caulk. You then use a caulk gun - trim the tip of the caulk tube and pump it into the crack.

You don't explain anything about your construction methods - so I have no way of knowing what you're caulking up against.

For a 1/4" caulk joint - you shouldn't exceed 3/8" in depth - the rest (behind the caulk) should be filled with a backer rod - 3/8" should be fine - you can get these at Home Depot.

Rod

you don't explain anything about your

Sorry for not getting into more detail, Rod.

A bit too late for backer rod unfortunately. Anyway. The actual construction is abit radical. But it's basically 2x2 framing hung with approximately 330 springs from the ceiling joists. Yes, that is 330. You read correctly. So anyway - the ceiling diaphragm was then drywalled (hopefully will stay somewhat rigid). The basic idea was that any 'footfall' or mechanical vibration from the upstairs neighbours would necessarily need to travel THROUGH the springs first and thus (hopefully) be dissipated by a large amount. Sounds QUIET so far!

Anyway - the ceiling stops about 1/4" short of a coninuous plywood shear wall at the perimeter. Perimeter drywall only comes up 1.5" short of ceiling (no contact possible). So that's pretty much it - a .25 in gap between ceiling and shearwall. Seems this is a pretty critical juncture..!!

Incidentally I stuffed 2x layers of drywall, 2x layers of the heaviest roofing paper (alternating, of course) and R30 between the ceiling joists- THEN the 2x2 frame w/drywall.

But I've read a LOT of stuff on mastic being the way to go for this app. elsewhere by pretty serious players. What makes acoustic caulk different? Where can I get it and do you have a spec for me? (mfr/model, etc..)?

thanks
Jonathan

Try urethane caulking.Dense enough to stay, drys like a rubber gasket.Very messy if not properly applied.