Double Garage Studio Design - Melbourne, Australia (7/10)

[rockindad]

Progress...wall painted. Well that was NOT a fun job!

Front external wall painted.jpg

Sooo, thinking more about the roof and what to do. An alternative idea is to extend the back wall (where the door is) up to the roof structure so that it is one solid 'outer' leaf all the way from floor to roof, and then clad 15mm plywood in-between the framing in the cavity above the studio space, fixing to the battens. I think it will be a little less soul destroying than getting the first plan into place...?

Roof design mk2 - internal baffle 2.jpg

Roof design mk2 - internal baffle 3.jpg

Thoughts...?

[rockindad]

Still working designs...here's version 3, which is a variant of version 1.

So first question is...can I get rid of these diagonal braces? They are not attached in any way that makes me thing they're integral to the structure, and in talking with a friend who knows stuff about such things...he suggested they were probably there to help hold the framing in place during construction.

Garage Studio Design - diagonal cross brace.jpg

So the idea involves fixing plywood to the underside of the roof joists and the horizontal braces.

Garage Studio Design - top outer leaf concept front top view.jpg

Garage Studio Design - top outer leaf concept top rear view.jpg

I'll put insulation in-between the joists and horizontal braces...of course.

Thoughts?

[xSpace]

Still working designs...here's version 3, which is a variant of version 1.

So first question is...can I get rid of these diagonal braces? They are not attached in any way that makes me thing they're integral to the structure, and in talking with a friend who knows stuff about such things...he suggested they were probably there to help hold the framing in place during construction.

When a roof is fully sheathed with plywood/OSB then that would be correct, the diagonal bracing is temporary. But this is not a fully sheathed roof. It has batten that does not generate the required ability for the roof system to act as a unit under external impact. So as it stands they need to be left alone.

The cracks you have witnessed in the block structure are a direct result of settling. The red iron beams designed to span longer distances are(as best as I can see) not attached specifically to the structure in a contiguous manner. This is a heavy roof in need of all the existing support it currently has, or some form related closely to all the pressure points.

Again, as best as I can see, the joists seem to go from front to rear in an unbroken path. Typically you would find a beam in the middle of the structure to break up that distance and allow for shorter, less potential to sag joists and also give the builder additional area to support the roofing system. This does not seem to be the case here.

Installing the sheathing on the underneath side of the rafters with the proper nailing pattern would seem to address the shear required. Problem is that this introduces weight that was not considered part of the engineers equations when this was designed. If a 1.5 safety margin was used initially then you may well be removing the "1" with this type of loading, effectively reducing the already moving structure to a ".5".


The red iron trusses with kick bracing cannot be removed as the current design is. The trusses allow the bracing for the roof a place to sit and support the roof, with the other kicker tied into the ridge aiding in support of the bracing against potential deflection.

What do you think of this proof of concept for sealing up the large gap between the I-beam and the roof created by the eave construction?

I'm not sure I'd do it that way: the underside of the roof deck usually needs ventilation, which is why the eaves are open in the first place. With that type of situation, you may have no choice but to do a three-leaf ceiling, and leave that ventilation space between the outer leaf (roof) and the middle leaf (mass you add under bottom chord of the trusses). So you could seal up above the beam like that, yes, but only as far as you need to go to get up to the middle leaf.

There is no venting in this roof system as it stands. There are no gable vents and there are no soffit vents. The only venting it is getting is from the uneven tile placement that allows some venting, not as much as it needs, but better than a complete zero. With the current design idea, that I wouldn't do btw, the need for venting may prove necessary to allow the mitigation of potential condensation being trapped.

[rockindad]

Hey Brien, thanks for your thoughts again...

When a roof is fully sheathed with plywood/OSB then that would be correct, the diagonal bracing is temporary. But this is not a fully sheathed roof. It has batten that does not generate the required ability for the roof system to act as a unit under external impact. So as it stands they need to be left alone.

Roger that. So you're saying that adding plywood to the underside of the rafters in the manner suggested may come close to meeting that stability requirement in your estimation, however the additional weight concern might undo that stability..?

The cracks you have witnessed in the block structure are a direct result of settling. The red iron beams designed to span longer distances are (as best as I can see) not attached specifically to the structure in a contiguous manner. This is a heavy roof in need of all the existing support it currently has, or some form related closely to all the pressure points.

Again, as best as I can see, the joists seem to go from front to rear in an unbroken path. Typically you would find a beam in the middle of the structure to break up that distance and allow for shorter, less potential to sag joists and also give the builder additional area to support the roofing system. This does not seem to be the case here.

The steel/iron trusses are bolted to each of the ceiling joists (horizontal beams?), which do go from front to back in an unbroken path - BTW the drawing is not 100% accurate as to the dimensions of the trusses - so the joists are supported at two points in the span.

The red iron trusses with kick bracing cannot be removed as the current design is. The trusses allow the bracing for the roof a place to sit and support the roof, with the other kicker tied into the ridge aiding in support of the bracing against potential deflection.

Is the kick back bracing those W-shaped frames that are on the truss? Still learning the language!

What do you think of this proof of concept for sealing up the large gap between the I-beam and the roof created by the eave construction?

FWIW - I've done away with that idea as it left very little room for ventilation...but will need to bridge the gap between the proposed sheathing and the cross beam. Along the following lines...

Garage Studio Design - sealing between outer leaf seathing and existing structure.jpg

This means there will be a ~110mm gap all the way up the roof deck - albeit filled with glass fibre insulation.

There is no venting in this roof system as it stands. There are no gable vents and there are no soffit vents. The only venting it is getting is from the uneven tile placement that allows some venting, not as much as it needs, but better than a complete zero. With the current design idea, that I wouldn't do btw, the need for venting may prove necessary to allow the mitigation of potential condensation being trapped.

The level of venting for the roof system seems to be completely standard in these parts as far as I can tell. Brien, can you suggest an approach I should take? I've been trawling thru various threads trying to get a look at other's solutions, but I'm not finding what I need...I don't think!?

[rockindad]

About to start working on the internal framing. One thing I wanted to clarify. The internal frame that I'm going to build should not be fixed in to the existing ceiling joists...is that right? So as to avoid flanking paths etc. It should be free standing.

Then should I also be putting new joists across this internal structure to hang the ceiling? If I was going to hang the ceiling on the existing joists would I need to use resilient channel? Yes or no? Is there resilient channel that can handle 16mm drywall?

Also, thinking that some variant of option one (the smaller/lower frame) for the roof space most because it doesn't fix into the rafters. Thoughts?

[xSpace]

About to start working on the internal framing. One thing I wanted to clarify. The internal frame that I'm going to build should not be fixed in to the existing ceiling joists...is that right? So as to avoid flanking paths etc. It should be free standing.

Then should I also be putting new joists across this internal structure to hang the ceiling? If I was going to hang the ceiling on the existing joists would I need to use resilient channel? Yes or no? Is there resilient channel that can handle 16mm drywall?

In a fully decoupled environment these are the things you do. You want to completely break the path that sound can travel on, so yes the ceiling joists should sit on the new framing.

As to adding mass to the existing joists, in your case I would ask that you not do that.

[rockindad]

As to adding mass to the existing joists, in your case I would ask that you not do that.

Do you mean, don't hang the internal ceiling from the existing joists?

I had a thought, to solving the dilemma I face with the outer leaf not being sealed, would be to simply add mass to the top of the existing joists, with 15mm plywood (which is easy to get here). That way I'm not adding mass to the rafters and creating any potential problems up there. Yes?

It means the gap between inner and outer leaf there is somewhat small (approx 100mm), but I believe it would be better than not doing it. Yes?

[rockindad]

Started the internal frame...

East wall frame.jpg

One down three to go.

For the west wall (which will be the back wall nearest the door - opposite this wall - I was thinking I'd do an inside-out wall there to get some extra depth to the bass trap that will require.

[rockindad]

Ceiling/Roof Space dilemma #325....!!!!

Would love some feedback on this soon as I'm in the process of framing...

South internal frame in progress.jpg

So, just when I think I have a solution I find a problem with my solution....

Had decided the best solution was to fix plywood sheets to top of the existing joists, seal that up and call that my outer leaf...then support new joists on my inner leaf (with a span of 4650mm) and hang the ceiling from them. Simple right?

I have an relatively low ceiling as is...the floor is very uneven....so my lowest point (North-East corner) would have a completed ceiling height of around 2300mm...with the far corner (South-West) will have a completed ceiling height of around 2380mm....so with that in mind I am going to have to fit my new joists in-between the existing joists.. (make sense?). The current joist are approx 100mm and are supported by a steel truss...

Ceiling joist and truss detail.jpg

1. Can I use a 90x45mm (max single span 2600mm) and support it off the exiting truss - using the truss as an overbatten - with some sort of isolated hook?
2. Lose more ceiling height (which I'm hoping to avoid!) - and use the prescribed 130 x 45 mm beam which I can do single span unsupported?
3. Some other genius solution that I haven't yet arrived at...

Love some feedback soon...please

[rockindad]

I was toying with the idea of interleaving beams to support my internal leaf ceiling...and then I read a lengthy post from Stuart about inside out ceilings vs interleaved beams....and well, I'd prefer to do the inside out ceiling idea...but...

a) Doesn't that leave me with only one leaf in my scenario? Would I need to somehow create a second leaf above the top layer? Or does my roof, although unsealed, act as an outer leaf of sorts?
b) What about flanking? If I'm using the existing ceiling joists that would lead to flanking. Does the benefit outweigh this effect?

[rockindad]

Progress to date...

Outer leaf front wall seal.jpg

Inner north wall top seal.jpg

Been working the details here...just filling all the gaps between joists.

Going to put 19mm particle board (see link below) as the top leaf for an insideout ceiling.
http://www.bunnings.com.au/structaflor- ... g_p0460721

I'm going to do an inside out wall for the 'back' wall (west wall) as well. The front and side walls will be 16mm drywall.

Two inner walls to frame and HVAC to sort.

[rockindad]

Progress pics...
South wall frame complete...with some miscellaneous insulation material.

South internal frame complete.jpg

Dismantled a couple of partitions I'd made for other purposes and re-purposed the insulation (white stuff is Tontine and the other stuff is rockwool).

rockwool in I-Beam.jpg

Got some rockwool behind these puppies as well - these are to be attached to the internal wall soon...now that the insulation has gone in the gap at the top of the air gap.

Inner north wall top seal.jpg

So next things on the agenda: Apart from more caulking!
HVAC - in particular the ventilation side of things. I'm thinking of using 200mm flexible ducting. Is that too big? I'm concerned if I go too small that there will be too much noise? ...anyone?

I'll build two silencers out of 18mm plywood (plans to follow). I'll make the room out-take active with an inline fan like this:
http://www.pureventilation.com.au/produ ... lead-plug/
Based on the calcs in Rod's book, If I have four people, I'm going to need about 1080m^3/hr, which this should deliver.

I will vent to and in-take from a roof cowl like this:
http://www.pureventilation.com.au/produ ... kit-200mm/
The room in-take I'll leave passive and let negative pressure do it's thing.

Electrical: I need to work finalise my lighting...still not 100% sure which way to go on this? Also number and location of power outlets.

Feel free to jump in with some thoughts....anytime....

Scott

[rockindad]

Progress pics...using up some insulation I had in a couple of partitions I'd made for other purposes. Mineral wool and the white stuff is Tontine. I was wondering whether there would be any benefit to filling the space between the walls with the fluffy insulation such as the Tontine? I have read it would increase the low end absorption...is that true?

South Wall insulation part 2.jpg

Made a bunch of these to seal the wall all the way up to the top layer which will be at the top of the joist.

Inter joist plug south wall.jpg

Like this...

Iner joist plug in-situ.jpg

Now...more caulking.

[Soundman2020]

I was wondering whether there would be any benefit to filling the space between the walls with the fluffy insulation such as the Tontine? I have read it would increase the low end absorption...is that true?

It's not that there is a minor "benefit" from doing that: rather, it's that there's a huge detriment to NOT doing it!

It works like this: Your inner-leaf and your outer-leaf act like a mechanical system where two heavy things are connected by a spring. That system has a natural resonant frequency, at which it loves to vibrate. It doesn't want to vibrate much at other frequencies, especially ones that are above twice it's natural frequency, but at it's natural frequency, it REAALLLLY wants to hum along.

That's why you tune your wall to a frequency at least one octave below the lowest one you need to isolate.

So far so good. But there's still this whole "resonate" story. It turns out that there isn't just one frequency where resonance goes on with a wall, but rather there's a whole bunch of them. And at each of those frequencies, the wall does not isolate very well. Instead, it passes that frequency through to the other side

Well, what if you could do something to the wall so that it did not want to resonate so much, not even at it's natural frequency? In fact, you can. You can "damp" the resonances in the wall, by adding something that absorbs the resonant energy inside the cavity itself, in much the same way that the shock absorbers in your car absorb the resonance in the suspension system. Without that, your car would bounce and wobble all over the place every time it hit even a small bump, and would go on bouncing and wobbling for many long seconds. The shock absorbers prevent that, by "damping" the resonance, and greatly isolating your car body from the road surface vibrations.

And in exactly the same way, the correct type of insulation inside your wall cavity damps all of the resonances inside the wall, absorbing the energy, so that it is not transmitted to the other side.

If you leave out the insulation, then that can cost you at least 5 dB and perhaps as much as 16 dB of isolation. That's HUGE! It's about the single biggest thing you can do to your wall, after adding mass to it, to make it isolate better.

The insulation works like this: As the sound waves pass through the air inside the insulation, they cause some of the air molecules to hit some of the fibers that make up the insulation. The fibers move and flex, absorbing some of the impact and converting it to low-grade heat energy. So the sound gets converted to heat.

But it has to be the correct type of insulation for optimum performance. Not just anything will do. If you use fiberglass insulation, then you want stuff that has a density of around 40 kg/m3. But if you use mineral wool, then optimum is about 50 kg/m3.

Using the correct type of insulation, and filling your entire wall cavity with it, is just as important as ensuring that there is no physical contact at all between your outer-leaf and your inner-leaf, and just as important as sealing every last bit of your wall air-tight.

Like this...

I'm not sure what we are looking at there. Is all of that your outer-leaf? I hope so. Because if that second frame is your inner-leaf, it looks like you are somehow connecting it to your outer-leaf with those wooden things, which would be a big mistake. Or maybe it's just the camera angle, and those wooden things are not actually touching the inner-leaf framing at all?

Maybe you can take some more clear photos to show what's going on up there, because it seems to me that the two leaves are joined up there, or are about to be joined, but keeping them entirely separate is key to getting good isolation...


- Stuart -

[rockindad]

Hey Stuart - thanks for dropping by...

Using the correct type of insulation, and filling your entire wall cavity with it, is just as important as ensuring that there is no physical contact at all between your outer-leaf and your inner-leaf, and just as important as sealing every last bit of your wall air-tight.

Roger that!

Or maybe it's just the camera angle, and those wooden things are not actually touching the inner-leaf framing at all?

No pics to prove it, but those things have a 3-5mm gap which I intend to gap with a low modulus caulk like this...
http://www.bunnings.com.au/tremco-600ml ... -_p0960273