# Need suggestions for HT project



## badbrad (Sep 2, 2008)

Hi all. Im new to the forum and this will be my first build.
Im starting constructon from the ground up on my room...literally (pouring my cement floor this week) I was just wondering if there was anything I could/should do before I start pouring the concrete. I would like to soundproof as much as possible, as I have two young children ages 1 and 7. 
As it is right now the dimensions are 18'6"long, 12'6"wide and after floor is down the height will be 7'7" high although the ductwork may take another 6 or 7 inches off that, leaving me with roughly 7'. Is this a suitable size for a HT?
The walls are all poured concrete excepting one side which is block (18' 6" side) and I plan on building a 2X4 wall all around and insulating then adding single sheet 5/8 drywall. But I'm still a little puzzled as to how the stud wall attaches to the ceiling without transfering the sound. Is there some sort of rubber thats fit between the top plate and joists?
Also, what is the best way to do my ceiling? Insulate between floor joists and double up on the drywall? Is that not going to transfer the sounds into the structure also?
Sorry for all the babbling but i really want to get going on this, and I don't want to jump in without asking some people with know-how first as i hate doing things twice.
Any advice or suggestions would be very much appreciated.
thanks in advance...and great site I must add


----------



## bpape (Sep 14, 2006)

Hi Brad

Welcome to the forum.

Isolation is a very deep subject. If you really want isolation, you'll need to isolate the walls as well as the ceiling or the sound will flank right around anything you do just to the ceiling. To do it right, you'll build your walls 1/2" short of the joists and use PAC International DC-04 clips to tie the walls to the joists above. 

If you can get the height back via duct routing, you can use PAC RSCI-V clips and hat channel to decouple the drywall from the ceiling. If not, then just use 1x firring strips perpendicular to the joists above and tie the drywall to that. ALL surfaces should have 2 layers of drywall and Green Glue or don't bother with any of them. Definitely insulate ALL of the cavities above and around the room.

You'll also need to plan ahead for isolation of the room's HVAC system (flex duct run in MDF boxes with 90 degree bends in them). You'll also need to box in ALL electrical outlets, switches, lights, etc. or you'll lose anything you've gained. 

Think of the room as an aquarium. It doesn't matter how big or where the hole is, you're going to get wet if there's a hole.

As for height, try to minimize the low ceiling as much as possible. Potentially have them route ducting around the perimeter of the room if possible.

Bryan


----------



## badbrad (Sep 2, 2008)

ok, i went down and checked it out and it looks as tho i can run my ductwork around the outside for most part. I may even be able to run them over far enough in the other part of basement to run them in between floor joists which would be even better. While we're on the topic of hvac, would it be wise to replace the existing tin/steel with a flex instead or will it not matter with the clips and double drywall you mentioned?
Im also wondering if there is an alternative to the green glue? Silicone? Acoustic caulking? ceiling tiles? haha
Im trying to stay under $3000 with the construction and the clips just about eat up the funds
thanks again


----------



## bpape (Sep 14, 2006)

Great news on the ducting. Yes - flex where it has to enter the room and what is FOR the room is a great idea.

Not really a replacemet for Green Glue - sorry. The DC-04's should cost you around $200 or so. RSIC-V, I'd have to figure. Firring is cheap. You'd be better off with Green Glue and firring than clips and 1 layer of drywall quite honestly. Look at it this way - even if you just used Liquid Nails (you have to have something between layers), it's still going to cost you over half of what the Green Glue would cost you and give you nothing in return other than no rattling between layers. That said - it would still be better than 1 layer of drywall due to the increased mass and lower resonant frequency.

If you need to spread it out, you can conceivably add the GG and 2nd layer later though it would mean box extensions, remounting the door, etc. But, getting the major construction right up front saves a lot of other hassles later. Yes - it's not an inexpensive product but it does wonders to help isolation. I'm guessing (WAG here) you'd likely have about $650 in Green Glue for that room. Also remember that with it, you can do 2 layers of 1/2" instead of having to do 5/8 which will save some money (and your back!)

Unfortunately, isolation isn't inexpensive. If someone could come up with a product that was inexpensive that would do even close to the same job, they'd make a small fortune. Everyone is looking for it - just doesn't exist. 

Bryan


----------



## badbrad (Sep 2, 2008)

Thanks for the help Bryan, things are fitting together nicely so far. 
What about avoiding clips altogether and instead of a "room in a room", build a sort of "house in a room"? By this i mean instead of decoupling from the existing framework in the room I make a double top plate on my staggered walls and run rafters between the existing floor joists. Not all the way up to the floor but maybe a 2X6 so i still have room for insulation (i have 2x10 floor joists) It would kinda be like a staggered ceiling but not be connected in any way.
I only need enough strength to carry the weight of the drywall right?
I have access to lots of lumber (2 uncles in the logging business, and one with a sawmill)
Is this a possibility??


----------



## bpape (Sep 14, 2006)

Absolutely. That's the BEST way to go but most people don't have free runs through the entire room. If you can build the walls 1/2" short, use DC-04's around the perimeter, and set the new joists between the old ones directly on the wall - that's perfect. You'll still want the double drywall but you can definitely save some height this way. That's exactly how I built my room.

Bryan


----------



## badbrad (Sep 2, 2008)

Oh yea, for sure the double drywall now. Without having all the clips for a hung ceiling to buy brought down the cost a fair chunk...might even go with the double 5/8 now. 
Are the clips around the perimeter for upper stability of the room?
And if so, what if i dropped some 1/2" L shaped rod into the concrete floor when i pour it and tightening my bottom plate down good and tight (with a good gasket underneath of course) to make the base more rigid. Then just framed the corners in the same as you would a typical corner wall in a house. Then, other than the floor there would be absolutly no contact whatsoever?
Im not really THAT cheap of a guy...its just that whatever i dont burn on construction costs goes into equipment :bigsmile:


----------



## bpape (Sep 14, 2006)

Understood. You really should have something on top to tie it in though. The idea with the DC-04 is that the long leg will flex a little and the rubber 'feet' allow the wall to move but provide a shearing force to resist it which is taken up by the longer leg. 

If you want to save a little money (and your back), just use double 1/2" for the drywall. The 5/8 will help a little bit but IMO with the construction you're going to do, it's not worth the money and the hassle.

Bryan


----------



## badbrad (Sep 2, 2008)

Thanks again Bryan. Point taken..I'll go with the DC-04's. Spaced every 2 feet I would only need abot 30 of them anyways. What would you suggest for a good base gasket in this case? I have lots of styro gasket, but im guessing that might not be a real good bet if the walls are being torqued down to the cement floor.
And I've been reading alot about what R value fiberglass to use..R-13 ok...hope so cuz i have 6 bags in garage just taking up precious space.


----------



## bpape (Sep 14, 2006)

For DC-04's you'll need 2 for each corner (1 within 6" of the end on each wall of each corner) - 8 pcs total - plus 1 every 2' in the field (another 26) for a total of 34 clips.

Under the wall, I use sill gasket like they use to lay down the sill plate on your house on top of the concrete before they bolt it down. Then, caulk both sides of the baseplate to the floor. The gasket is just there to take up the gaps that are uneven. The caulk is what's really sealing things. 

You'll also need to caulk the bottom of both layers of drywall down. If you have larger gaps at the bottom, use backer rod to take up most of the space then caulk on top of that.

Bryan


----------

