hello again Steve. I feel like I've covered more ground tonight than I have in the past year of dreaming.
I know offhand the roof is held up by manufactured trusses, I think 5 across the 10' width of the garage, maybe six. I'm sure I seen a few airbrick above rafter height on the outside of the garage...it's gone 1am here and I'm not lookin for a flashlight to go check Can't do digital pics. I don't remember the roof being sealed when it went on...I'm guessing I'll need to use that expanding foam stuff the double glazing firms use inside the loft area of the roof where it meets the walls...beyond that I really have no idea what direction I should be going in.
Got out the tape measure today (was going from the original plans before) and realised some of my sizes were off.
Length 25'3"
Width 9'7"
Height to roof trusses 7'6"
height above trusses to roof peek 5'7"
There are 2 airbrick (hollow with latticed fronts on the outside of the building) each the size of two house brick on top of each other about 10' up the wall above the roof rafters evenly spaced about 8' apart.
The roof is made up of 6 identical manufactured trusses (see pic below) stepped across the 9'7" width of the garage. 6 trusses with 5 gaps, from the house side out the gaps are 24", 24", 24", 24", 16½". The beams used in the trusses measure 5"x1½"
As previously posted, if I'm floating my ceiling on my inner walls and floating floor what do I do with this roof space? This seems to be my last obstacle on the design front. Once I know how to treat it I can start calculating the materials and a cost (oh no, the cost!)
I'm now looking at room sizes of:
Control room: w 8'6" x L 12" x H 6'8"
Live/drum room: w 8'6" x L 8' x H 6'8
that still leaves me a 3'6 x 5' space at the back after taking the door into consideration to maybe add a vocal booth
" don't remember the roof being sealed when it went on...I'm guessing I'll need to use that expanding foam stuff the double glazing firms use inside the loft area of the roof where it meets the walls" -
You definitely do NOT, repeat NOT, want to seal that roof area with expanding foam or ANYTHING else - it was vented like that intentionally so that the moisture that collects in your attic area from condensation, etc, gets a chance to DRY OUT from the air circulation - this is fine, and pretty much what I expected - however, I've been caught off guard by the unexpected a couple of times so I always ask rather than assume.
All this means, is that you'll need TWO mass leaves for your ceiling separated by an air/insulation cavity - I'm on my way to another 12-hour day shift followed by 2 12-hour night shifts, so don't have time right now to lay out what you need to do for your ceiling - Please don't seal up those air bricks though, that would be a big mistake. I'll work on a couple ideas in the next couple days.
Meantime, when you get the chance if you could check availability on materials such as drywall sheets in 1/2" and 5/8", and lightweight 25 gauge steel framing studs, at least 3-1/2" wide or more, that would help.
the drywall is't a problem Steve, I live a few streets away from a building supplies company I've done a lot of business with in the past. Steel studs? I was thinking timber, or is the steel for the ceiling?
Actually, what I was thinking about is a couple layers of gypsum wallboard directly on your ceiling joists (the underside of the trusses) followed by some light gauge (25) 3-1/2" steel studs (gives aur/insulation space and FLEXIBLE mounting for the second round of wallboard layers) then 2 more layers of wallboard (1/2" and 5/8" ) - If you have access to Resilient Channel, you could use slightly heavier steel studs between your two leaves of gypsum, then put the Resilient channel on before the inner two layers of wallboard - that would let you leave your attic ventilated, and still give two leaves of mass with one air?insulation space between them. That would give best isolation with minimum headroom loss.
In every case, your best sound proofing will be had with mass-air-mass construction - each center of mass should wrap completely around the space to be soundproofed, and NOT touch the other center of mass. Any sound should have to go through mass/air/mass to get in or out. Nothing more, nothing less.
If you draw a plan for construction, you should always check to see if this rule is followed - simply pretend you're a sound, and you're trying to get from one room to the other, or from one room to outside, etc - in ALL cases, to escape you should have to get through mass, then air/insulation, then mass. If there's another barrier in the way, you will actually have LESS isolation than with just two.
I tried to find time to do a drawing of the ceiling idea for you yesterday and today, but work has been 12 hours of non-stop hell on wheels lately.
What if I layed 2 layers of gypsum (staggering the seams) directly onto the roof truss beams on the underside, then used acoustic sealant (Caulk?) to seal this against my rendered walls.
Then I use a ceiling design same as the walls underneath on top of my floating floor and walls but maybe use 3 layers of gypsum, or a layer of plywood sandwiched with 2 gypsum layers.
That way my room (rooms...I'll be building 2 seperate floating rooms inside the garage) will stay detached.
This still confuses me slightly though, as I'll have a ceiling of 3 layer Gypsum (MASS) insulation/air the 2 sheets of gypsum on the rafters (MASS)
so that gives me my MASS/AIR/MASS ceiling and it's detatched from the main garage.
BUT, above the rafters I still have another BIG airgap and more MASS consisting of the double sheeted 3ply, roofing felt and tiles that make up the roof?
will this 3layer gypsum/ansulation/2ply gypsum give me a good enough STC rating? because anything that gets through that is gonna go floating fight out the 2 airbrick before it gets a chance to hit the roof.
I'm sure there's a simple answer but it seems every time I try to think things through myself I end up digging a large unnecisary hole for myself.
Hi guys - may I butt in here. Alec that wall drawing you posted came from the SAE site. On the same page I describe a ceiling system that matches. What Steve has advised is totally correct - when you seal off the ceiling under your trusses that seal will go to the rendered brcik wall. The next question is how to create leaf 2 - your ceiling. Steve's suggested correctly that you can hang a second leaf off the first one using RC.
In my plan I span the new ceiling from the new inner walls with the drywall on top and a treated 703 layer below - so you create your second leaf which is mechanically disconnected from the outer ceiling as well as treating the inner surface acoustically - just like the walls are doing. With a low ceiling like yours it's advisable to treat it totally with 703 as it is so close and parallel to your bright floor yet you maintain your high end brightness by using additional slots and panel absorbers on you walls. Not completely covered, maybe 50%.
The blue existing ceiling in your drawing is the 2 layers of drywall I'll be fixing to the rafters of the roof trusses. Below that I'll have my isulation (703? or the UK equivalent), 2 more drywall layers on a wooden frame filled with more insulation for acoustic treatment.
So I understand I'll get a better STC using RC between the rafters and the drywall I'll be sealing to the rendered walls, before floating my ceiling on my new walls.
Can't do digital pics. I don't remember the roof being sealed when it went on...I'm guessing I'll need to use that expanding foam stuff the double glazing firms use inside the loft area of the roof where it meets the walls...beyond that I really have no idea what direction I should be going in.
Alec that wall drawing you posted came from the SAE site. On the same page I describe a ceiling system that matches. What Steve has advised is totally correct - when you seal off the ceiling under your trusses that seal will go to the rendered brcik wall. The next question is how to create leaf 2 - your ceiling. Steve's suggested correctly that you can hang a second leaf off the first one using RC.