Prepping the basement for drywall

[Velvet Elvis]

Hey Rod, Fitz and Knightfly...

Its been forever, but I am approaching the drywall time of the studio rooms in my basement. I'm actually taking this week and next week off of work to get it ready.

As a refresher, here's what's going down... its a studio in a poured concrete basement. Drywall will be 2 layers of 5/8 hung on RC for walls AND ceiling. Floors are not being floated.

Outlets are all normal wall outlets, but all will be wrapped with firestop putty and caulked with OSC-175.

Studio use will be project/semi-pro with live guitar amps and SOME occasional drums recording.

I do have a couple of questions though:

1) The tops of the basement walls are your typical "I-beam on top of a sill" construction for modern houses. This is above the ceiling level of the rooms, but is still going to be a factor I'm guessing. It will be VERY hard to seal them, as they are stuffed with plumbing, HVAC etc from the floors above. I will seal any obvious voids (like where the HVAC fresh air vent etc breaches the outer OSB) and plan on stuffing that with insulation. Do you think this will work sufficient for the studio?

2) The soffit framing around the HVAC and such in the basement was done with OSB and 2x4s - IE - the carpenter used the OSB for the vertical drop and then spanned with 2x4s across the bottom. The construction is VERY sturdy, but if I put my RC and 2 layers of drywall on the side of the OSB, I've essentially created a 3-leaf system (albeit for a small portion of the wall). Would it be better to attach drywall directly to the soffits in these areas and forgo the RC?

3) I pulled all the insulation out of the walls (long story related to water issues and such) and therefore need to replace it. With no insulation in the walls, I have the chance to either put in rockwool or standard fluffy stuff. I've heard both suggested for various reasons. Which would be better for dealing with drums/guitar amps?

If you would like pictures of any of the areas I am talking about, I'd gladly put some up.

Thanks!
Jim
Velvet Elvis

 

[Glide]

Are you going to use green glue between the sheet rock layers?

 

[Velvet Elvis]

No... I'm doing four rooms (home theater and three studio areas) and could swing the cost for the green glue.

Jim

 

[Ripthorn]

If you really want to isolate between the rooms, look into putting some deadsheeting in either between your drywall layers or behind. That will act as a pretty good sound barrier if you plan on loud sounds (like in a home theater when it's an action sequence). Of course, that stuff can get a little pricey. Also, are you doing single stud, staggered stud or separated stud wall construction?

 

[Velvet Elvis]

Single wall construction, but resilient channel on one side for part of it.... double (completely separate) walls with resilient channel on the rest.

All layers are TWO layers of 5/8 inch drywall.

Jim

 

[Freudian Slip]

I think I paid $160 or so for a six pack of the BIG tubes of green glue. It got me a long ways in my space. Sounds like your dumping money as it is. You only get to go through this phase once. Seems a pitty not to throw that extra $160 at it and at least do the important walls.

F.S.

 

[Velvet Elvis]

I think I paid $160 or so for a six pack of the BIG tubes of green glue. It got me a long ways in my space. Sounds like your dumping money as it is. You only get to go through this phase once. Seems a pitty not to throw that extra $160 at it and at least do the important walls.

F.S.

The Green Glue site says your are supposed to use one small tube per every 4x8 sheet of drywall. I have 125 sheets of drywall. Divided by two, that's ~63 sheet of drywall. 63 sheets of drywall = 63 tubes of Green Glue. At $177/12 tubes (according to Green Glue's site), that's $929 worth of Green Glue plus shipping.

If it were just an extra $160, I'd do it in a heart beat, but $929 is a little out of my reach right now (after buying everything else for the construction).

I also checked locally to see if anyone had Green Glue at a lower price, but the local drywall supply house only carries OSI Pro Serios 85... which I doubt has the same acoustical properties.

Jim

 

[Freudian Slip]

The Green Glue site says your are supposed to use one small tube per every 4x8 sheet of drywall. I have 125 sheets of drywall. Divided by two, that's ~63 sheet of drywall. 63 sheets of drywall = 63 tubes of Green Glue. At $177/12 tubes (according to Green Glue's site), that's $929 worth of Green Glue plus shipping.

If it were just an extra $160, I'd do it in a heart beat, but $929 is a little out of my reach right now (after buying everything else for the construction).

I also checked locally to see if anyone had Green Glue at a lower price, but the local drywall supply house only carries OSI Pro Serios 85... which I doubt has the same acoustical properties.

Jim

Bummer... I did used it on the exterior walls with 3 layers of 1/2 inch. About 25% of the exterior walls are 12" of cement so that helped. The interior walls were built in and disconected from the outside walls so I just put up a single layer of 5/8 there.

Things will get more tricky when the CR project fires up. That's where I will be really isolating as much as possible.

well if you can't do it all you might want to consider doing the connection control room walls. Good luck and have fun. Just got done with a whole house

F.S.

 

[Velvet Elvis]

Yeah, mine is of a similar construction to yours... the outer leaf of the majority of the walls is solid concrete... BUT at the top of the concrete sits the sill for the floor framed above it. To me, this seems like a REALLY weak point in the sytem. IE - I'm not worried as much about sound going out through the concrete and into the ground (though I understand it can certainly do so), but I am very worried that sound will flank the first leaf via the ducting for the HVAC and exit out of the sill area to the outside.

Jim

 

[Freudian Slip]

Yeah, mine is of a similar construction to yours... the outer leaf of the majority of the walls is solid concrete... BUT at the top of the concrete sits the sill for the floor framed above it. To me, this seems like a REALLY weak point in the sytem. IE - I'm not worried as much about sound going out through the concrete and into the ground (though I understand it can certainly do so), but I am very worried that sound will flank the first leaf via the ducting for the HVAC and exit out of the sill area to the outside.

Jim

Well I am 20% concrete. The rest is framed with chip board coverd in hardey plank on the outside.
I know that you mean about on top of the wall plate (foundation in yoru case) being a tough one to tackle. Most of my basement is above ground and I live in a hoa. I decided because I was going to have a dropped cieling with 5/8 inch DW that I would take my chances with the floor joist area at the outer wall. The floor joists have a end cap (2x12) with plywood & hardey plank on the outside of that. I hope it's not an issue, but if it is I will have to come up with something. I have used 1/2 inch thick rubber conveyor belt for stuff like that before. It weighs a ton and deadens pretty good. You can cutt it with a utility knife as well.

You have actual air ducting going outside for your HVAC? I only have tubing running out for the a/c condensor. I am worried about ducting between the rooms though. Luckily There is a pretty long run between the CR and the next vent in the circuit. If I have to I will build a removable blocker plate for the vent in the CR.

Good Luck

F.S.

 

[Velvet Elvis]

You have actual air ducting going outside for your HVAC?

No, I'm talking about the ducting into the rooms that I'm trying to treat... even though the walls will be two layers of 5/8 on RC, the duct work is only tin, which means I'm assuming the will conduct sound through the wall and into the ceiling cavity. Once in the ceiling cavity, sound could exit our the sill plate area.

I'll be caulking around the vent hoods and such, but I'd have to image that those tin pipes transfer quite a bit of sound through the walls.

Jim

 

[Freudian Slip]

No, I'm talking about the ducting into the rooms that I'm trying to treat... even though the walls will be two layers of 5/8 on RC, the duct work is only tin, which means I'm assuming the will conduct sound through the wall and into the ceiling cavity. Once in the ceiling cavity, sound could exit our the sill plate area.

I'll be caulking around the vent hoods and such, but I'd have to image that those tin pipes transfer quite a bit of sound through the walls.

Jim

Ahhhh. I see what you mean.

F.S.

 

[Glide]

Contact this guy - he can get your green glue in the price range you want. I bought 5 cases from him in that price range.

The board will not let me post urls until I have 5 posts. PM me for his URL.

 

[Velvet Elvis]

Rod, Knightfly, Fitz, John...

Any comments from you guys?

I'm still concerned about the bleed from the HVAC tin and from the sill area. I'm also questioning what to do over the soffits (that are already covered in 1/2 inch OSB).

Had 120 sheets of 5/8 inch drywall and the resilient channel delivered yesterday... wow is that a lot of rock.

Today I pulled all the outlet boxes out of the entire area (regular boxes) and replaced them with the adjustable depth boxes. I know I could have used the plaster rings etc to extend them, but I wanted to make sure I could get them sealed properly with the putty... so I decided I'd just replace them with proper depth boxes. Now I can move them out the entire 1 3/4 inches that the wall depth will be!

Tomorrow night I wire the home theater stuff and start wrapping outlets with putty.

Starting to make progress.

Jim

 

[Rod Gervais]

Velvet -

first off - save some money - any walls that are isolated do not need resilient channel - in fact it will LOWER the TL value of you walls in the lower frequencies - not raise it.

So save a few bucks.

Next - if you have a weak point at the framing above ceiling - then you have to fix that by installing some drywall there with caulked edges......... as far as the sill itself goes - stuff some fiberglass in there - (don't pack too too tight) then backer rod and then caulk it.

I'd need to see some details in order to comment on the HVAC - I do not have a clear picture based on your description.

Rod

 

[RICK FITZPATRICK]

Rod, Knightfly, Fitz, John...Any comments from you guys?

Yea, listen to Rod. Although I have some comments myself, Rod is the expert here and his opinions are based on real world experience. Mine are based on a gut feeling. Nevertheless, heres a few.

First off, without the aid of any SECTION or DETAIL drawings at every exterior wall, interior partition and their connections,door details and HVAC soffiting and duct plan, it would be very difficult for even an expert to visualise the multitude of possible planning mistakes, not to mention the actual construction mistakes made by tradesman no matter how skilled they are. Due to unfamiliarity with the technical requirements of "isolation" construction, one little incorrect connection could possibly render all planning in that regard as moot.

As to postulating suggestions per your questions, I have a few of my own.

Unfortunately, I have to leave shortly and don't have time to address your questions untill tonight. But I'll be back.
fitZ

 

[Velvet Elvis]

Rod,

I'll take some pictures and show you what I'm dealing with tonight.

As for the RC - the ceiling is on the floor joists for the first floor, and the walls connect to that - so I was under the impression that RC would be needed in order to combat it all being connected. Is that not true?

The HVAC question is pretty much simply this: There's a hole cut in the drywall for the HVAC vents. I understand that I can caulk the vents, but what keeps sound from escaping (or simply moving the ducting with vibration) from the HVAC ducts themselves? It seems like the metal boot itself would translate sound past your wall and into the cavity between rooms/above the ceiling/wherever.

Jim

 

[RICK FITZPATRICK]

As for the RC - the ceiling is on the floor joists for the first floor, and the walls connect to that - so I was under the impression that RC would be needed in order to combat it all being connected. Is that not true?

This is exactly what I was talking about. Clarity of intent makes for concise answers Yea, it would appear that ....IF....you have FASTENED the partition framing directly to the floor joists above, then the ONLY way to decouple the drywall in the rooms below is via RC or other types of iso hardware. However, I see a problem brewing here. Jim, IN MY OPINION, in order to use RC on only ONE side of a partition framing, to keep structural transmission of vibration from occuring from the OPPOSITE sheithing, to the framing, and on to the floor membrane above, is to isolate(decouple) the partition framing from the floor membrane above via SWAY BRACKETS. It would appear now, that to keep BOTH FACES of the drywall on a given wall framing decoupled, is to use RC on BOTH faces and the cieling.

However, this may be a moot point depending on understanding the implications of the following 2 considerations:

As for the RC - the ceiling is on the floor joists for the first floor, and the walls connect to that

PLEASE clarify if you fastened the top plate of the wall partitions THROUGH exisisting cieling drywall. Here is why. IF...your intent was to leave an EXISTING drywall cieling in place, and then fasten RC OVER the existing drywall, and then fasten another layer of drywall to the RC, your wasting your time and RC. The reason is you will create a THREE LEAF system.

And depending on REALLY UNDERSTANDING the next one, there may be no reason to RC at all, as the HVAC ducting may render all this work useless.....that is . if I understand the following statement correctly... and I SINCERELY hope I do not. Please tell me the SAME ducts that either supply or return air in the basement, do NOT feed ANY rooms above?????????

The HVAC question is pretty much simply this: There's a hole cut in the drywall for the HVAC vents. I understand that I can caulk the vents, but what keeps sound from escaping (or simply moving the ducting with vibration) from the HVAC ducts themselves? It seems like the metal boot itself would translate sound past your wall and into the cavity between rooms/above the ceiling/wherever.

In my opinion, IF, these SAME BASEMENT DUCTS supply or return air to the rooms below as well as to rooms above, vibration from the ducts into the ceiling cavity is the least of your problems. IF I AM CORRECT, and these same ducts do indeed feed rooms above and below....I'm afraid you have failed to understand the meaning of DIRECT FLANKING PATH!!!

And I sure hope i'm wrong. At this point, I don't think I have anything else to offer untill this issue is clarified FULLY.

Other than, thats my opinion. Maybe Rod has a solution. Personally, if this is indeed the situation, I think some SERIOUS re-evaluation must be made.

fitZ

 

[RICK FITZPATRICK]

PS...I REALLY don't understand this:

There's a hole cut in the drywall for the HVAC vents

A hole cut in WHAT drywall???? Are you saying that the EXISTING CEILING DRYWALL has holes cut in it, and you plan on EXTENDING EXISTING DUCTS THROUGH THE NEXT LAYER of drywall that STILL has to be placed??? Jim, please clarify this stuff.

 

[Velvet Elvis]

Rick,

I'm about to grab some pictures - which I will post... but let me answer some of your questions.

Yes - the interior walls in the studio area are connected to the cement floor via tapcons and to the ceiling joists via nails. Most of the walls were existing framing (as required by code when the house was built), so this wasn't necessarily a design choice as much as it was a "this is what I have to start from" choice.

The walls are NOT drywalled at this time... only framed.

Many of the wall areas and soffits also cover HVAC trunks to the remainder of the house (this is a basement, so it is to be expected), so I was fully expecting to have to do RC everywhere (walls and ceiling).

PLEASE clarify if you fastened the top plate of the wall partitions THROUGH exisisting cieling drywall.

Nope... I'm NOT fastening through any existing walls. The top plate is connected directly to exposed floor/ceiling joist. The RC would be hanging directly on the studs.

Please tell me the SAME ducts that either supply or return air in the basement, do NOT feed ANY rooms above?????????

The same TRUNKS connect the areas. IE - the whole house (including the studio area) shares a single HVAC unit. There is a trunk at the end of the house from which feeds for two upstairs rooms and the three studio rooms all connect. Same with the return line. That being said, ALL of the feeds and returns independently connect back to the trunk. The studio runs also are using flex ducting (for both feeds and returns) and include a few bends and turns. There are NOT any situations where a feed or return splits at the end and feeds multiple rooms.

In my opinion, IF, these SAME BASEMENT DUCTS supply or return air to the rooms below as well as to rooms above, vibration from the ducts into the ceiling cavity is the least of your problems. IF I AM CORRECT, and these same ducts do indeed feed rooms above and below....I'm afraid you have failed to understand the meaning of DIRECT FLANKING PATH!!!

My comment/question about the HVAC hole being cut in the drywall is simply this: the ducting for HVAC is far from "air-tight", so you cut a hole is a finished room (a room to be finished in this construction phase) for the boot of the HVAC... it seems that even though you can seal around the boot, the ducting wouldn't be sealed and would still leak tons of sound into the cavity ABOVE (beyond) the walls... which in turn would be picked up by any other vents in that same ceiling space, whether physically connected or not.

Perhaps the flex ducting is enough to curb this (since it decouples the metal from other metal), but it still doesn't seem like it would make the HVAC system air-tight and therefore sound proof in any manner.

Does that make sense?

Let me grab the camera and go take some pictures... be back shortly.

Jim