Author Topic: Green Glue and Cementboard  (Read 7147 times)


  • Guest
Green Glue and Cementboard
« on: September 14, 2007, 11:27:37 PM »

First post!

We are basically extending (extruding) our master bedroom out to create a new space for a master bath.  This is on a second floor so we'll lose a vaulted ceiling over the formal dining room below.

The wall between the new master bath and our master bedroom is of chief concern.

I'm planning a 2x6 with staggered 2x4s and doing GG between 2 layers of 5/8" drywall on the master bedroom side.  However, the bathroom side is going to be tile, tile, and more tile...pretty much everywhere (not looking forward to that bid!  ;) ).  I plan to lay cementboard on a fair amount of this wall.  How does GG do with cementboard?  How should I do it?  One layer of cheap 5/8" drywall and then a layer of the pricier cementboard with GG between?  Also, what insulation, if any, should go into this wall?

How do folks normally "handle" such thick walls when it comes to the door?  If i calculate correctly, I'm looking at a wall that will be 7.5 - 8" thick.  Regardless, I guess I want a nice solid wood door on this bathroom.

Oh, this wall will have plumbing it it...double sinks and a toilet will live on the wall.  The shower and tub are much further away on the opposite wall.

Thanks!  :)


  • Guest
Re: Green Glue and Cementboard
« Reply #1 on: September 15, 2007, 12:53:24 AM »
Honestly, skip the Green Glue. 

Since you're going with a staggered stud wall with insulation and a layer of drywall + cement board on the bathroom side, I doubt you need green glue.  If you pay attention to caulking and sealing gaps in the wall construction, you'll get an STC rating of 51-52 through that wall, more than enough isolation.  Adding Green Glue would probably only get you another 2-3 points, too little to notice.

And since you'll have a door in your soundwall, most of the sound energy is gonna leak through it anyway.  Green Glue won't help there... 

You might want to liberally paint the backside of the cement board though - sound can leak through all the pores and holes.

Fiberglass insulation works just fine.  Cotton works marginally better, but at 5 times the price.  Decide how much you want to pay..

A thicker than normal wall will require a custom door frame.  Will cost you more (maybe 50 bucks) and might have a longer lead time, but easily done.  Talk to your builder.   

Having plumbing inside the soundwall is usually not a good idea, but if it can't be avoided, try to get another layer of drywall on the bedroom side to kill some of the plumbing noise.  Use foam pipe insulators on all supply lines and mount the pipes resiliently, in rubber bushings.  If the pipes are rigidly mounted to or touching the studs, the vibration/noise are going to transfer.  If at all possible, try to get  a cast-iron waste stack.  PVC pipe is extremely noisy.   


  • Guest
Re: Green Glue and Cementboard
« Reply #2 on: September 15, 2007, 04:00:06 PM »
Thanks for the response and advise.

I had planned for the master bedroom side of the wall to be 2-layers of 5/8" drywall with GG between them.  Do you still think the GG is worth it for this side of the wall?  I'm happy to not spend the money on the GG if it doesn't appear that it will buy me much.

Yeah, I cannot avoid plumbing in this wall separating the master bedroom and master bathroom.  I think all the plumbing in this wall will simply be copper lines for water but I'll ensure they are mounted resilienlty and insulated and sealed well.

Another issue is that the new master bath causes a loss of a vaulted ceiling below and this in turn, to make plumbing much easier and cheaper, means I need a 3" DWV heading down the one of the walls of the room below, which happens to be the formal dining room!  Yes, I plan to ask the plumber to make this pipe cast iron.  It'll cost more in parts and labor but the noise supression, as you point out, will be much better.  He can switch it over to PVC once he is under the house.

Excellent...thanks so much.  :D


  • Guest
Re: Green Glue and Cementboard
« Reply #3 on: September 15, 2007, 11:50:47 PM »
Personally, I'd skip the Green Glue.  You're not exactly building a recording studio, you just want to quiet the noise in the master bedroom.  And your plan is an excellent, cost-effective way to do that - you're good to go.