New Guy with 24'x10'x7½' Garage with very close neighbours

[lemontree]

Hi, I'm Alec. Been a lurker for far too long, so here's the deal.

I have a 24x10x7½ Double Brick garage stuck on the side of my house. On the other side of the garage is a lane/walkway about 5' wide giving access to 6 houses running parallel with the long side of my garage. My neighbours gardens are a further 20' long before you're on their back doorstep. So I've got 25' between my outside garage wall and my neighbours back door entrances to their houses.

I'm thinking double stud wall on the 3 outfacing garage walls and a single stud on the wall joining the house as there's a staircase and a utility room on the otherside (no main living/dining/bedrooms).

The garage roof is arched 7' in the centre of the 24' wall, so I'm thinking most of that area can be sound treated to leave me my 7½' headroom below (still not a lot if I want to float a floor, I know)

I'll be taking away the tilt & push garage door and double bricking the entrance. That only leaves me one way in and out via a 30" door on the back of the garage.

I've attatched a pic of a rough design. I haven't included any acoustic treatment, basicaly I just want to know if this will work without pissing off the neighbours if I do it correctly.

All suggestions would be greatly welcome, thanks

Alec.

[VSpaceBoy]

Well John designed this for what looks like a perfect fit.

[lemontree]

that would only give me 9' front to back in the control room. Plus I have drummers carrying their kit through the control room , I might go with this...

[knightfly]

"I'm thinking double stud wall on the 3 outfacing garage walls " -

Not a good plan. You want best isolation you can get without losing a lot of space, right? You should read through this thread -

http://johnlsayers.com/phpBB2/viewtopic.php?t=598

And then, see if you can tell me why putting two more walls inside your double brick walls is a near total waste of time, space, and money. (Not a gag, and I'm not being a smart-ass, trust me) You said you'd been lurking, but you may have missed some vital info in that thread... Steve

[lemontree]

I read the entire post. Looks like the inside out wall design would be better for my limited space. I'm working on a new layout without the vocal booth, a 7' x 9' drum/live room and a 13#' x 9' control room. With a floating floor I should still have about 6'9 headroom. If anyone wants to suggest anything different my ears are open. Thanks again,

Alec.

[knightfly]

Whether you go Inside Out or Upside down, one of the points I had hoped you'd find was that you don't want more than ONE air space with TWO centers of mass, one on each side of the air space (insulation counts as air) between any two areas you're trying to isolate. More usually = LESS.

IF your double brick walls are SOLID (no weep holes at the base) then you may be able to use only ONE layer of gypsum spaced off the walls for your second leaf - this would give within 1-2 dB of the same isolation as more layers (the bricks help) but with more "panel trap" effect - if you set your inner leaf spacing away from the bricks you could "tune" this extra trapping to a potential room mode problem frequency... Steve

[lemontree]

That went straight over my head.

My understanding was, for best sound proofing results I needed to build a room within the existing room (in this case my garage) and the inner room should be built on a floating floor and no part of the inner room should touch the outer. So I take it I MUST leave an air gap between the inner room and the garage. If you're then telling me that insulation counts as air and I should only have ONE air space in my construction, then I can't have any insulation on my inner wall? That's crazy!

This is what I intended (after reading the thread you kindly pointed out)....

[knightfly]

Sorry, I neglected to mention that insulation or air WITHOUT another mass doesn't matter from a soundproofing standpoint - your diagram is a proper double-leaf wall - the bricks being the outer mass, the insulation/air inside that is the ONLY air space that matters much, then the double layer of drywall is your SECOND leaf; inside that is just acoustic treatment, which might have a small detremental effect on sound proofing but not much. It's only when you SEAL things up reasonably tight (not allowing the air to escape quickly enough) that a mass makes much of a difference in isolation.

Your drawing might cause a slight loss of Transmission Loss at the frequency of the slat resonator you've shown, but pretty negligible. Realistically, you'd probably see more loss at doors/windows so it wouldn't be even noticeable.

I hope that cleared things up... Steve

[lemontree]

Your drawing might cause a slight loss of Transmission Loss at the frequency of the slat resonator you've shown, but pretty negligible. Realistically, you'd probably see more loss at doors/windows so it wouldn't be even noticeable.

I hope that cleared things up... Steve

It won't be noticable? the noise outside the building won't be noticable to my neighbours? Or my attempts at soundproofing won't be noticable?

I thought I had this pretty much wrapped up Steve. The elevating garage door if being removed and bricked up, double brick same as the rest of the garage. There's a small window in the rear next to the door which will also be removed and bricked up. The door at the rear is a good quality solid wood door on a very tight fitting seal. I also intend to give the full inside a skim of plaster to fill in any cracks (not that there are any that I can see).

the double layer of drywall is your SECOND leaf; inside that is just acoustic treatment, which might have a small detremental effect on sound proofing but not much.

So should I do away with the timber slats and use RC and more Gypsum? then apply acoustic treatment?

Alec.

[knightfly]

I think you're reading too much into some of my comments - when I said "negligible" I meant that it could be ignored. Your drawing is the way you should do it. Outside mass (bricks) insulation/air, inside mass (2 layers drywall)

Whatever you put inside that is for acoustic, NOT soundproofing, purposes. These are necessary, or you'll have a soundproofed CRAPPY sounding room. The fact that some types of acoustic treatment (such as slat absorbers) may have a dB or two of negative effect on overall soundproofing, cannot be helped. They are necessary.

You didn't show on your drawing whether you intend to do ALL the walls with slat absorbers - that's not a good plan, you need more variety than that.

Your brick walls should be enough of a barrier, along with the double sheet rock, that you won't have any sound leakage problems with your design.

Short form: It's good, build it ... Steve

[lemontree]

ok Steve, thanks. What's my other option to slots if I'm not to have them all the same?

I'll be honest, If everything on the inside of the gypsum is sound treatment and not sound proofing I don't think I trust this to stop the sound traveling to my neighbours 25' away

If anyone wants to throw in a "if it was me I'd do it like this......" I could do with the reassurance.

Alec.

[John Sayers]

Lemontree - your suggestion about rendering the inner brick wall will increase the STC of the brick wall. A standard house brick has an STC of 39 whereas a house brick rendered both sides (13mm (1/2") 1:1:6,Cement:Lime:Sand) has an STC of 45.

With the inside out wall you have 3 options of treatment.

1 - rigid fibreglass with a cloth cover - High frequencies.
2 - slots - low mid frequencies - high frequency reflective.
3 - panels like Ethan's panel absorbers - low frequencies - also high frequency reflective.

Thus you can cover the whole range without loosing additional floor space.

cheers
john

[knightfly]

OK, John's got your acoustics going - here's some idea of what you can expect for sound proofing. I don't know what you expect, but either of these is a damn good wall. Your brick (especially rendered) is your FRIEND, and the two drywall/air just clinches the deal.

Don't sweat it - BUILD it Steve

[lemontree]

Steve & John, huge thanks to you both.

With my wall plan in place I guess my next question would be the ceiling.

the garage doesn't have a ceiling as such, just open wooden beems 7½' high. Above that in the centre of the garage the peek of the roof is a further 7' above the rafters and slopes down to meet the rafters on the front and back at the ends of the building. The roof is double sheeted 5 ply with roofing felt and heavy tiles (this thing was built to last).

If I'm floating my ceiling on top of the walls on my floating floor should I treat the space above the ceiling? Or will this more layers and more air spaces reduce the STC?

Thanks again, you guys are great

Alec.

[knightfly]

Glad to help - on the ceiling, though, we'd need to know how your roof is vented/sealed, etc, before suggesting a ceiling plan. You still need to stick to the Mass-air-mass idea of the walls for good isolation, so if your roof is vented it doesn't count. Most roofs ARE vented, so things dry out and don't rot. Check it out thoroughly; exact spacing and size of framing members, whether the rafters are part of engineered trusses, maybe even a digital pic or two (please size them no bigger than about 700 wide), and let us know... Steve