Type BA Acoustic Metal Deck

[bookowski]

I'm doing a small penthouse addition on an existing building. It is basically a steel framed box. While this is not really a structural question does anyone have experience with sound transmission of using only metal roof deck + insulation in a space like this. The architect is asking if sound such as rain will be evident through the roof. It would not be easy to get concrete up to the space and they are also trying to keep it as thin as possible. What about type BA acoustic deck? Never used it and not really sure if this is the intended application.

 

[JAE]

I think the acoustic deck deals with sound generated within the building and knocks down echoes and reverberations from within. I don't think it does much with sound generated from outside (above) the building such as rain pounding on the roof. (or hail).

 

[mbullism]

We've used BA before without negative feedback, however I post this because we did have one job with an issue... the acoustic deck was requested by the architect for an auditorium, and vetted by their aucoustics consultant. Less than a year after construction we received a call asking if the roof structure had enough "reserve" capacity for them to strip off the roofing and insulation and place concrete or lightweight fill instead...

Apparently, the rigid insulation on the deck with an applied membrane acted as somewhat of a snare drum, to the point that one especially significant downpour "drowned out" their guest speaker at a commencement...with a microphone...and postponed the event.

To be fair, I have no idea if the acoustics of the space were such that using standard type B or any other decking would have mattered...

fyi

 

[j19]

I don't know much about sound transmission but I looked through some old files and came up with the attached document. Unless you can consider using a metal roof over the top of blanket insulation then it probably won't help you very much

 

[EngineerofSteel]

The Steel Deck Institute Manual may help:

http://www.sdi.org/whites/moc2.pdf

I also have a steel deck question open at the same time, and I found it interesting you have one as well. I'm reading through the manual now.

p. 9 of 48 is the first mention of acoustic deck.

 

[bookowski]

JAE - I think you're right, the more I looked into it it seems the intent is for sound reverberating off the deck from inside.

MBullism - thanks, the 'snare drum' effect is what I am worried about.

I found that Georgia Pacific has some info (STC Ratings) when using their 'DensDeck Roof Boards' on top of roof deck. In their tables they compare to metal deck with rigid insulation alone and it doesn't look great. It looks like the Dens Deck is basically just adding mass in terms of acoustic improvement. At some point I guess it makes sense to just get concrete up there instead. Will update this if I get any better info, I'm going to bug an acoustician.