Basement ceiling and furring strips - AVS Forum
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post #1 of 13 Old 11-06-2005, 10:14 AM - Thread Starter
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I've read in several posts that a "poor man's" alternative to RSIC clipping the ceiling is to run furring strips 90 degrees to the floor joists for attaching two layers of drywall (GG in between) to. I'd like to understand this alternative a little better and what the satisfaction level is for those that have done this.

What size furring strip was used?

Was anything used between the furring strip and the joist?

What thickness drywall was used?

What percentage coverage was used for Green Glue?

What technique was used for transitioning from ceiling drywall to wall drywall?

Any fear of sagging the furring strips over time?

I'm already (at least I think I am) aware of the other things I'll need to do at the ceiling, such as replacing A/C runs with insulated flex duct, deadening the backs of registers that feed the upper floor, treating recessed light cans, etc.

Any info, including how it compares to the more professional methods, is greatly appreciated.

TIA - monsoon

Even Frederick thought his grandfather's work was doodoo before he gave it a stab
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post #2 of 13 Old 11-07-2005, 03:52 PM - Thread Starter
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Come on now... I know it's been done... I've seen the pics ;)

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post #3 of 13 Old 11-09-2005, 06:53 PM - Thread Starter
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One last hopeful bump...

Even Frederick thought his grandfather's work was doodoo before he gave it a stab
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post #4 of 13 Old 11-09-2005, 09:56 PM
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I hate to see your questions completely ignored, so even though I have zero personal experience in this matter, I'll relate what I recall:

1) 1x2 or 1x3
2) Some have opted for Integrity Gasket
3) One 5/8" layer and one 1/2" layer
4) Totally based on your budget, I believe
5) Leave a 1/4" gap and fill with caulk
6) No clue

I'm frequently finding that I have an oddly selective memory these days regarding information I've gleaned here, so please proceed with a healthy dose of skepticism. :rolleyes: (If nothing else, perhaps any errors I've made will inspire a correction by someone more knowledgable!)

--BadAstronaut
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post #5 of 13 Old 11-09-2005, 10:51 PM
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Hey Monsoon,

I did furring strips on my ceiling, and while I have little with which to compare, I am currently happy with the results ('current' because I am still in the midst of taping/mudding the drywall). More details about what I did can be found on my construction thread, but the long/short of it is that I used integrity gasket combined with furring strips and nail plates to do what you are talking about. I hadn't seen anyone employ my exact solution so far, but it seemed to work for me. Worked really well, actually. The only real sound I get is flanking noise through the door and through the ducts (I didn't replace my ducts with flex).

In doing it again, I'd probably do the same thing, although my needs are different than many of the posters' needs. My noise containment and isolation from the upstairs is fantastic. I hear very little. If I were to change anything (don't know if I would), it may be in doing RC1 channel rather than the furring strips. I wasn't the one that was going to hang the drywall, so I didn't want the possibility of shorting it out...thus the furring strips and nail plates.

To answer a couple of your questions:
Green Glue - if you are going to do double drywall then it's very effective. I can't speak to using it between joists and drywall, since few use it solely that way. I would guess it works very similar to how the integrity gasket between joist and drywall work, but not sure. Were you planning on doing two layers of drywall, back to back?
Sagging - I don't believe there is much chance of sagging. I've talked with several builders about the issue, and they just laughed. I used 1x3 furring strips, just to be sure.
Thickness of drywall - My ceiling joists are aprox 10 inches deep. I filled that with R-19 insullation, then put up the integrity gasket, furring strips, nail plates, integrity gasket along the length, and finally 5/8 inch drywall (single layer of drywall). Prior to doing any of this, I could hear the TV in the living room through the floor/ceiling of the basement. I could tell every step that anyone upstairs made, and the sound seemed magnified (small bumps upstairs sounded like people jumping on the floor). Since doing the steps mentioned above, I can't hear the TV at all, even when turned to extremely loud volumes. I can't hear people walk. I occasionally hear when my sons are running upstairs, or chasing the dog, etc. but it is very buffered (and they are impact noise, which is incredibly difficult to resolve).

With noise going from basement to upstairs, it is even better. I haven't caulked yet, so some of this is flanking noise through the 20+ recessed lights, but I can't hear anything from the basement. I turned the music from my computer (in the basement) up much louder than I would typically listen to anything, went to my bedroom which is directly above it, and couldn't hear anything (I finally heard it when I went very close to the vent). I put the air compressor right below my bed and fired it off, then went upstairs to listen...could here a minor white noise (initially thought it was the air conditioning, until it stopped). The solution has been great for me...can hardly wait to see how it will be once I have caulking, taping, sound treatments on the walls, some carpet to absorb some sounds, and some bass traps (along with furniture). I am betting it will be much better than my expectations.

Let me know if you had any specific questions regarding it...otherwise, good luck. I think my efforts have gotten great results, and anything more that you did could only get better. With that in mind, I don't think there's a wrong way to go.
-Scott
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post #6 of 13 Old 11-10-2005, 08:22 AM
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I didn't use furring strips-- I used 2x3s. I'm not done yet, so I can't comment on performance.
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post #7 of 13 Old 11-18-2005, 05:27 PM - Thread Starter
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Scott (handcuff),

You're information is WONDERFUL. This is the sort of stuff I was hoping to see. I'll re-read it a couple of times to digest it better but I do have an immediate question:

What are the "nail plates" you refer to?

TIA - monsoon

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post #8 of 13 Old 11-19-2005, 09:03 PM
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Thought this would help. I spoke to Ted White from Audio Alloy and got some help with my theater. Here is what he had to say:

1. Double dry wall all around 5/8 then 1/2. Use green glue in between for
all walls and ceiling.

2. No RSIC clips needed, there is nothing wrong with going the furring strip way (budget)

3. Put 3/8" to 1/2" furring strips joists where ladders are not used to decouple the ceiling from the joists. Attach the sheetrock to these strips. Consider damping the strips (2 layers of plywood + Green) if you have the space. Use construction adhesive on the joist to hold the furring strip, and use WOOD screws, not drywall screws to hold up the furring strips.

4. Build can light boxes out of 1/4" duracrete (inside) 1/2" plywood/MDF outside laminate with green glue for all the lights to recess them inceiling. run wire through a hole and caulk it with decent caulk. Green Glue isn’t a caulk, so use a silicone in this area due to heat and durability. You can Green Glue the plywood to the Cement board, though.

5. Drop wall sheet rock right to floor

QUESTION: Should ceiling sheetrock butt up againast the wall sheetrock?
YES, No cracks. If you were going with clips, you’d leave a gap. No clips = no gap.

6. Caulk all seams with cheap caulk, but use everywhere

7. Mud first layer of sheetrock, no tape. mud and tape second layer of
sheetrock. If you are covering second layer with acoustic treatments (I hope you are…) then no need to mud and tape at all, unless there is a building code issue.

8. Weatherstrip the french doors. Big Time.

9. Buy an external door for the furnace room. Yes, exterior steel or fiberglass works

10. Run caulk between sheetrock edges and squish them together when putting
up sheets

Hope this helps you...

Gary
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post #9 of 13 Old 11-20-2005, 08:53 AM - Thread Starter
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Scott,

Never mind about the nail plate question. I know what they are. It was just one of those days :o

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post #10 of 13 Old 11-20-2005, 09:24 AM - Thread Starter
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Gary,

Its really nice to hear about the feedback Ted White gave you. I've been slowly coming back up to speed on the rather large GG thread. I had read through it a while ago and now it seems twice as long!

I've just a few questions about your list if you don't mind...

No. 3

a) You use the term "ladder". I"m familiar with its use when referring to soffets. What are you referring to under your context?

b) It sound as though you are saying "build your own furring strips" by ripping plywood into strips. Is this correct? The idea of sandwiching green between two strips of ply is interesting. If I've read all this right, is there a recommended width for the plywood strips?

No. 4

a) Is the duracrete providing protection from the heat generated by the light cans? This would seem right to me. Is this an accepted industry practice that "should" satisfy most building codes?

b) Do you have any photos of how the boxes were installed between joists and how they meet up with the ceiling sheetrock?

No. 5

Why all the way to the floor? Why not a small gap backfilled with flexible or accustic caulking?

No. 10

Is the word "squish" really part of The He-man's Guide to Acceptalbe Construction Terminology :D


Thanks for the great info!

monsoon

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post #11 of 13 Old 11-20-2005, 04:52 PM
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Quote:
Originally Posted by monsoon
Gary,

Its really nice to hear about the feedback Ted White gave you. I've been slowly coming back up to speed on the rather large GG thread. I had read through it a while ago and now it seems twice as long!

I've just a few questions about your list if you don't mind...

No. 3

a) You use the term "ladder". I"m familiar with its use when referring to soffets. What are you referring to under your context?
I am referring to wood as soffits (very large one accross the whole ceiling) to cover all the duct work.

http://www.geocities.com/garykagan/_P1011765.JPG

Quote:
Originally Posted by monsoon
b) It sound as though you are saying "build your own furring strips" by ripping plywood into strips. Is this correct? The idea of sandwiching green between two strips of ply is interesting. If I've read all this right, is there a recommended width for the plywood strips?
I will be using 1x3 furring strips. I did plan on using plywood but then went with the 1x3 as they are ready to go! Here is my pile against the far wall.

http://www.geocities.com/garykagan/_P1011767.JPG



Quote:
Originally Posted by monsoon
No. 4

a) Is the duracrete providing protection from the heat generated by the light cans? This would seem right to me. Is this an accepted industry practice that "should" satisfy most building codes?
Not sure about code or if I even need the duracrete. I'm actually thinking of returning all the duracrete and making the boxes out of 3/4 MDF. Not sure about a heat issus as all fixtures are attached to wood anyway.

Quote:
Originally Posted by monsoon
b) Do you have any photos of how the boxes were installed between joists and how they meet up with the ceiling sheetrock?
I will. I plan on making these boxes in the coming weeks and will post them on my thread. I have a plan to handle the double sheetrock and standard HD fixtures with require only about 1/2 to clip on.

Quote:
Originally Posted by monsoon
No. 5

Why all the way to the floor? Why not a small gap backfilled with flexible or accustic caulking?
Good question. Not sure. I think it may be better to leave a gap off any concrete floor and fill with caulk. I may actually do it that way.

Quote:
Originally Posted by monsoon
No. 10

Is the word "squish" really part of The He-man's Guide to Acceptalbe Construction Terminology :D
It sure is. Look at page 69.
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post #12 of 13 Old 11-21-2005, 02:22 AM
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Quote:
Originally Posted by monsoon
I've read in several posts that a "poor man's" alternative to RSIC clipping the ceiling is to run furring strips 90 degrees to the floor joists for attaching two layers of drywall (GG in between) to. I'd like to understand this alternative a little better and what the satisfaction level is for those that have done this.

What size furring strip was used?

Was anything used between the furring strip and the joist?
I think this suggestion stems from Audio Alloy's labs. The strips we have used fall into two basic categories: 1x3 / 1x4's and plywood laminated with Green Glue (typically 1/2 ply / gg / 1/2 ply)

Quote:
What thickness drywall was used?
same options as for any other type of assembly

Quote:
What percentage coverage was used for Green Glue?
same basic tradeoffs with coverage as exist for any other Green Glue wall. 50% coverage is only somewhat of a compromise relative to 100%, and Audio Alloy hasn't thoroughly explored the use of even less Green Glue than that (than 50% coverage).

The primary consideration is cost, if you are on a budget, use 50% coverage.

Quote:
What technique was used for transitioning from ceiling drywall to wall drywall?

Any fear of sagging the furring strips over time?
i always refer people to their local building offices with any question of a structural nature.

Quote:
I'm already (at least I think I am) aware of the other things I'll need to do at the ceiling, such as replacing A/C runs with insulated flex duct, deadening the backs of registers that feed the upper floor, treating recessed light cans, etc.

Any info, including how it compares to the more professional methods, is greatly appreciated.

TIA - monsoon
what do you mean more professional methods? not every acoustical consultant recommend flex ducts, although the ducts will have to be dealt with. if you have a designer, confer with them, otherwise search this forum.



I would like to add some thoughts on furring strips. Audio Alloy has spent alot of time/resources looking into the construction of walls, and one of the priorities, obviously, has been to outline cost effective methods of sound isolation construction. much/most of our work has focused on Green Glue.

I suspect that the furring strip concept originates here, and it is effective, particularily in combination with Green Glue. This does not represent an RSIC clip, this does not represent a true decoupling scheme. In essence, what you accomplish is (assuming 16" OC joist or stud spacing) expanded "stud" spacing. In combination with damping, wider spacing is effective because part of the function of Green Glue in a wall is the dissipation of energy over distance. using furring strips 24" OC provides more distance over which the GG can dissipate energy.

To shed some perspective on this situation, we tested GG + furring, GG + RC, GG + RSIC , on 2x4 studs, 16" OC. RSIC hat channel, RC, and furring strips were all 24" OC. drywall was normal 1/2" drywall.

The performances for RC and RSIC were about as one would expect, showing the decoupling behavior typical of these products. As one would expect, the RSIC wall offered a lower decoupling point (by virtue of lower resonance), and superior performance as a result.

The RSIC assembly performed best in the group from 80hz and up. the RC assembly performed better in the STC range than the assembly with furring strips (STC=57 -vs- STC=54), but worse in the subwoofer region (4-5 dB at 50/63hz).

Short-circuiting the RC assembly heavily (adding 16 short circuits on a 64 square foot wall section, or 8 short circuits per sheet) raised low frequency performance of the RC assembly to be in line with the furring strips, and lowered stc a little (the 16 short circuits dropped STC from 57 to 55).

The overall study could be discussed in great length (and will be on our site someday soon, although the RSIC data wouldn't ever be released w/o pac's permission), but the basic lessons are just that in combination with Green Glue the furring strips work better at low frequencies in combination with Green than RC because they create a more mechanical system, which is better controlled by the GG. Short circuiting the RC moves performance to very similar to that of the furring strips because the short circuits make the flexible RC assembly more mechanical.

It's worth mentioning that one benefit of GG is a virtual elimination of performance loss resulting from short-circuiting RC.

Do not tell people that short circuiting their RC walls will improve performance. These walls had GG and should not be equated to normal walls. With normal drywall, short circuits in RC can cause catastrophic failure.

do not tell people that furring strips work as well as RSIC clips, these walls had GG and should not be equated to normal walls. With conventional drywall the RSIC would enormously outperform the furring strips.


But what can be said, is that in combinatoin with GG, furring strips offer a nice way to improve performance, to yield performance approaching that of more exotic assemblies at basically zero cost/installation trauma.


On a ceiling, with a vastly deeper air cavity, the advantage will tip more heavily towards the clips (though not really towards RC). As i've said many times before, ceilings and their deep air spaces are a match made in heaven for clips. To summarize the results for these assemblies, in essence for theaters we ahve GG + RSIC > GG plus furring or GG +RC with short circuits, > GG + RC

i hope that clarified alot of the relevant points.

Brian

Understanding sound isolation
That link may be helpful
Brian
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post #13 of 13 Old 11-21-2005, 06:28 AM
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Quote:
Originally Posted by monsoon
Gary,
a) Is the duracrete providing protection from the heat generated by the light cans? This would seem right to me. Is this an accepted industry practice that "should" satisfy most building codes?

b) Do you have any photos of how the boxes were installed between joists and how they meet up with the ceiling sheetrock?
monsoon
Here are some pictures of how I am doing my light boxes.

The last picture shows how they will be installed between the joists. Basically, I attached 1X2's to the sides of the box extending them past the ends of the box by about 12 inches. I then rested the box on top of the RSIC hat channel between the joists. (I'll run a screw through the hat channel into the 1X2 to hold it in place.) This keeps the box totally decoupled from the joist. The box is installed so it hangs below the hat channel by 5/8". The first layer of drywall will be flush with the bottom edge of the box. The second layer of drywall will go beneath the light can with a hole cut for the recessed light.

(If you can put your recessed lights in soffits that you build AFTER the drywall is installed, you can avoid the whole lightbox issue).
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