Author Topic: soundproofing a metalworking shop  (Read 5388 times)


  • Guest
soundproofing a metalworking shop
« on: September 19, 2006, 04:22:02 AM »
I'm glad I found this site. I'm hoping you all can help me find the best, easiest and least expensive way to soundproof my newly constructed (framing finished) metalworkng shop. I do a lot of grinding, cutting, and welding. Many air tools are used so therefore the heavy duty compressor runs alot at times.

The shop is 22' X 18" with a 8' X 4' bump out for the compressor room.

Details of the shop:

* The shop has a slant roof and the ceiling height starts at 9' to 14' high.

* 2 X 6, 16" on center, exterior walls with OSB and will use HardyPlank (cement fiber board) for siding.

* concrete floor and crawl space underneath.

* 8' X 6' solid core french doors

I've been doing some research and I have information overload!  

So, here's what I'm thinking of doing...

5 1/2" cotton fiber batt insulation between studs

and crawl space.

I found that MLV is out of my budget.  

Someone suggested using smooth roofing membrane so

I think I'll go with that.

chaulk and tape all seams of roof membrane.

finish with 5/8" drywall and chaulk all seams.

I have no idea what the STC rating would be on this...

Anybody have any suggestions? Is this a good set up?

Few questions-

What kind of fastners should be used to attach the roof membrane to the studs? and for drywall?

Will using 5 1/2" Cotton fiber batt in a 2 X 6 wall have enough "dead air space"? as I have read somewhere that this is important ?

Should caulking be used on the studs before the drywall goes on to create a damper?

What kind of chaulk is suggested?

What kind of tape is suggested for sealing the membrane?

Well, that's all I can think of at the moment..

Thank you and I hope to hear from you,



  • Guest
Re: soundproofing a metalworking shop
« Reply #1 on: September 19, 2006, 06:16:06 PM »
Well, first of all, lose the french doors.  They look great but don't block sound worth spit.  (Or did you mean 'panel' doors, with no windows?  Those are OK, provided you have some good perimeter sealing.)

Also, lose the roofing membrane - it won't do much.

I'm assuming you want to hang stuff and cabinets on the walls, so you don't want to mount the drywall resiliently so double it up instead; maybe use some Green Glue between the panels.  This would be cheaper than MLV.  And in many ways, more effective.

The STC depends on whether it's and exterior wall and what's on the other side.  With 2 layers of 5/8" drywall, you'll get a good rating.

A 'dead air space' in the wall isn't that important.  Just make sure the insulation isn't packed in too tight, as this will diminish performance.  Having the insulation in there is much more important.

Caulking on the studs?  Why not?  It couldn't hurt.  Use 'acoustical caulk' (sold on this site).  It's cheaper than buying it locally and works better for the application, too.  Also remember to caulk up all the seams, field joints and edges, too.  And if you want, seal them with foil tape.  Cheap insurance.


  • Guest
Re: soundproofing a metalworking shop
« Reply #2 on: September 21, 2006, 01:54:21 PM »
Thank you for your quick reply johnbergstromslc.

As for the french doors, yes they are panel w/o windows. I need to pay attention to seal it  properly.

Not doing the roof membrane will save me some work..  :)

I will talk to my drywall contractor about doubling up on 5/8" drywall. Is there info on this site on recommended installation of a double wall? The drywall panels should be chaulked in between with 'acoustical caulk' ... right?

I'm confused on the best stc insulation to use-

*Cotton fiber


*Rock Wool

I've been told rock wool is best... I can't find stc ratings.
Then again, I've read cotton is better...  ???

Thanks again,



  • Guest
Re: soundproofing a metalworking shop
« Reply #3 on: September 21, 2006, 05:00:27 PM »
Yeah, I'd caulk anywhere there is a discontinuity in the drywall - edges, seams, gaps, penetrations.  And since foil tape is on 4 cents/foot, tape up the seams and edges, too.  Don't worry about the screws.

Any insulation you mentioned will work, including fiberglass.  Just don't use rigid foam or anything that will pack in too tight.  

Despite what you may hear otherwise, the insulation isn't a great factor in the STC value.  Having soft, absorptive insulation in the cavity raises the STC by about 5-7 points.  Most of the STC increase in your case is coming from the added mass and sealing.  

In order of increasing cost:

Rock wool

Cellulose and rock wool are a hell of a mess if you ever have to do demo (been there, recently - cough, cough).  Fiberglass is itchy and also gets in your lungs.  I guess cotton is the 'best' in the list and has slightly higher NRC (noise reduction coefficient) than the others but you'll definitely pay a premium price for it.

So don't sweat it too much, just decide how much you're willing to pay....


  • Guest
Re: soundproofing a metalworking shop
« Reply #4 on: September 25, 2006, 09:44:16 PM »
Hello welder,

The 5-1/2" thick bonded cotton insulation is a must! Forget the roofing membrane - it doesn't work for soundproofing.  Use Green Glue sandwiched between two layers of dry wall.  And put isolation tape on the studs to decouple from structure.  Acuostic caulk buttered on edges of dry wall as you install will insure no sound leaks through (as will making sure no dry wall seams line up with each other).

With the bonded cotton insulation, and Green Glue sandwiched between dry wall layers, and isolation tape on studs/joists you should get well over 70STC!