2 leaf, 3 leaf question

khallgren · Post by **khallgren** » Thu Aug 07, 2003 2:05 am

So I'm converting my two-car garage into a practice space, and trying to maximize the transmission loss between the space and the outside world.

I've learned the basic fact that two leaves (mass spring mass) is the way to go for this, and I've been working on adding mass to my existing walls by placing 5/8" drywall between the studs. Tedious, to say the least. I will follow this by framing an entirely new structure inside the newly beefed up outside one.

My question has to do with adding mass to the garage door side of the space. The door will be non-functional, but needs to remain intact for cosmetic purposes--I want the garage to still look like a garage.

I'm planning on framing and drywalling the wall the doors are on for my outer room. If I were to build the inner room, then, would that count as three leaves? The structure would be garage door then mass, space, mass. Does the garage door count as a mass since it is so poorly insulated? I've read on this board of people dis-regarding brick walls as a mass because they are perforated at the bottom (weeping bricks or something?) for moisture purposes--is this a similar situation? The garage door is the kind with several horizontal jointed panels that "roll" as the opener lifts the door. I will fix the door to the vertical inside track, then remove the opening mechanism and ceiling track to finish my room.

I can provide a drawing if that would help clarify what I'm talking about.

Thanks

Kraig

knightfly · Post by **knightfly** » Thu Aug 07, 2003 2:23 am

Kraig, no drawing will be needed here - Your assumptions are right on the money. The leakier the garage door, the better in this case. The more you vent an air space, the less effect it (and its associated mass) will have on the wall performance. Your plan should work well, just follow the other do's and don'ts of acoustic wall building repeated here so often.

Here is probably the best summary of those -

http://johnlsayers.com/phpBB2/viewtopic.php?t=529

Keep in mind that flanking noise can ruin an otherwise good design - if your other walls' inner layers are fastened directly to studs, they will transmit thru the studs to the rest of the building and you'll see a performance loss. Better if all your inner surfaces are resiliently mounted, not touching each other and then caulked with acoustic sealant thoroughly... Steve

khallgren · Post by **khallgren** » Thu Aug 07, 2003 2:33 am

That response was ultra-quick!

Thanks Steve.

From a purely construction-minded view, is there anything I need to do between the garage door and newly-framed outside wall? I live in south-eastern Michigan, USA. Hot summers, cold winters, wet springs and dry falls. Do I need a moisture barrier, or anything like that?

I suppose I should check with someone familiar with local building codes...

knightfly · Post by **knightfly** » Thu Aug 07, 2003 4:06 am

Checking with a local contractor would be good - I would think that you'd want to possibly ADD a vent somewhere to make sure you have air flow in front of the new wall - I'm assuming you're planning to build the frame and panel the outside of it while it's laying down, then tip it into place (into a heavy double bead of acoustic caulk) and then do the inside?

If so, you might check your local paint stores to see if they carry an additive for the paint that repels bugs - It adds about $5 per gallon to the cost, but since that area will be ventilated it might be good not to encourage the little critters to live there.

This is one downside of leaving garage doors in place - its not fun to keep the area clean between the door and the sound wall, since you almost HAVE to remove the tracks in order to finish soundproofing. It would be a lot easier to remove the door and frame in the wall instead. I know it can be a pain to have to comply with local "beauty rules", that's why I live in the country on 10 acres... Steve