Questions for Rod Gervais about his book, Build it Like the Pros

[jeffpardo]

I am. . I'm mainly a songwriter and producer in Nashville, and tour on keys with an artist named Matthew West.

If I was to add sheathing, what annealed glass sizes would I need? It's double walls, btw....but 2x4 construction due to space. So while I'm asking that, I'm also aware that thicker glass than 5/8 on 2x4 might get difficult to angle....I do want to be able to angle a bit.

[Rockenberry]

Rod,

On page 252 of your book is the ducting plan for the HVAC system showing the supply and return duct plan.

I will be doing a similar configuration but wanted to ask a couple of questions.

1. Using basic physics, air will choose the path if least resistance and thus if some duct paths are shorter than others, the shorter duct paths will be supplied with more air/have more air extracted.
Is this true?

2. If this is true, I take it I would have to make the duct lengths equal in all rooms. How would I achieve this if I am to have a combination of a supply plenum and branch ducts?

I ask as the duct paths in the diagram do not seem to be of equal length.

Thanks

Rock.

[Rod Gervais]

Rock,

You're missing the point of the book....... this is not written to teach you all about HVAC design - but rather to point out things that are critical in achieving a good studio design. I expect that anyone's HVAC contractor would be able to extrapolate from the book what was critical for success - and then use that as a part of their design criteria.

I also expect that anyone who will be taking a DIY approach to this knows enough to do the same.

I could devote an entire book to outline every nuance to a complete design - but then I would not have room for everything else. So I did not bother getting deeply into things like the various types of control systems that could be utilized..... VAV boxes, volume control dampers, etc., etc., etc.

To directly answer your questions however:

1. This may or may not be true - given ducts of the same size most typically the greatest flow will be through the take offs from the main trunk lines that are closest to the fan coil.

Thus if you consider a 20' branch off the main trunk near the fan coil - and a 5' run at the very end of the main - the 20' run may well have more flow (all other things being equal) then the 5' run.

2. Again - this is not (necessarily) true based on physics...... everything depends on everything else.... reality is that this is all based on the same principles as electricity - the path of least resistance is the deciding factor - and in order to determine that there is a lot more than simply the length of run.

Typically we provide volume dampers to the supply in order to balance duct systems. These could be inline, in which case if the dampers will not be directly available due to a hard ceiling or wall - remotely adjustable dampers are available.

Another approach is based on the principle of static pressure - where the duct size is adjusted in order to maintain proper flow without the need for balancing dampers - however this is very involved and also very expensive in comparison.

Hope this helped.....

Rod

[Rockenberry]

Rod,

Thank you very much! Like you said, I know I was going beyond the scope of the book in terms of asking a more involved questions!

Thank you all the same for answering my questions.

Rock.

[jeffpardo]

Last question from me, Rod....if my 3/8 and 5/8 laminated glass pieces are already cut, is there any advantage to adding green glue between the double drywall pieces in my double wall construction? Definitely willing to spend money on the glue, but don't want to just throw it away....

[eeags]

Hi Rod,

Quick question about your method for adding mass to the outer leaf. How important is it to add the 1x blocking when adding drywall between studs in walls? Is there a potential issue with just using the finish nails backer rod and caulk to hold the panels in place?

[jeffpardo]

You around, Rod? Curious about your thoughts on my green glue question above. Thanks man!

[Rod Gervais]

The laminated glass you're using is the equivalent of double layers of 5/8" on each face - so although you would get some benefit from the GG - you would not get the ful benefit in that particular wall - don't know if you would benefit from the other walls or ceilings - I don't have details enough to determine the answer to that.

[Rod Gervais]

Originally Posted by eeags

Hi Rod,

Quick question about your method for adding mass to the outer leaf. How important is it to add the 1x blocking when adding drywall between studs in walls? Is there a potential issue with just using the finish nails backer rod and caulk to hold the panels in place?

The nails are intended to hold the mass in place long enough to seal the edges - I would not trust them enough for a long term application - it would be a real bitch to get your walls all done and then a few years down the road to have the panels in there start rattling around.....

I detailed the furring because I considered it important - I really don't do things that cost money unless they are necessary.....

Rod

[trymonlam]

Rod, in my current room I have a ceiling beam issue. Please take a look at the following picture. The main beam that runs through the length of the room sits to the right of the listening position. I can either have it leveled for a reduced ceiling height of approx 7.5 ft, or I can build ceiling so it recessed into the space. If I go the recessed route, the beam will still be present. But in the area of recess I then have clearance of about 8.6 ft. So one way sacrifice ceiling height, the other can present a asymmetrical problem. How do you think I should proceed?

[Screaminlove]

Hi Rod,

on page 78, you wrote:

RISC-1 clips and hat sections can also be used on ceilings with the same results you get on walls. The advantage to using this system is that the drywall ceiling can run directly to the perimeter of the existing wall assembly. This solves issues with weak isolation points at that location, as well as creating a good seal for fireblocking.

I couldn't find a detail for that situation, and I'd like to get what you said right.

I understand that you can run the ceiling to the perimeter of the existing foundation (let's say your in a basement).
Do you run only the first layer of drywall, and seal the edge with fire caulk?

Then, can you screw the top of the 2nd wall assembly directly in the hat channel?

Thank you so much once again for sharing your wonderful knowledge!

[hally]

Hi Rod,
In the book you specify duct liner to line the inside of the Silencer Baffle box, here in Ireland ductliner is crazy expensive, as is 703 fiberglass. I am reluctant to use wrapped rockwool as i get the feeling it will disintegrate over time...

Do i have any other alternatives, for example, acoustic foam, if the latter is suitable, what density foam should i use and how thick should it be....

Thanks for your help

Warm regards
hally

[Rod Gervais]

Originally Posted by trymonlam

Rod, in my current room I have a ceiling beam issue. Please take a look at the following picture. The main beam that runs through the length of the room sits to the right of the listening position. I can either have it leveled for a reduced ceiling height of approx 7.5 ft, or I can build ceiling so it recessed into the space. If I go the recessed route, the beam will still be present. But in the area of recess I then have clearance of about 8.6 ft. So one way sacrifice ceiling height, the other can present a asymmetrical problem. How do you think I should proceed?

In order to get effective isolation you will need to wrap the beam - I would probably opt to create a matching false beam to maintain symmetry.

Rod

[waynel]

Hi Rod,

Thanks for writing your excellent book. I have the second addition and was planning on using a floor construction for a wooden deck similar to the one that you recommend in chapter 10. I've attached a diagram as well as a photo showing the area directly beneath the studio. This situation is a little different because there is nothing underneath the studio and I have a few questions.

1) Is it OK to omit the drywall underneath the floor joists? It's very difficult to install.

2) Do I need the gypcrete in this situation? Could I use 3 layers of plywood with green glue instead?

3) Will I get much benefit from the rigid fiberglass considering that there is nothing underneath?

Thanks
Wayne

[Kenny M]

Hi Rod,

Not really a question referencing a particular topic in your book, but since your book has served as a bible in my
construction of two studios in my building and that I didn't get any response to a previous post here on GS, I thought I'd run a simple question by you. Thanks for the great book.

I'm trying to figure out what dimension of lumber to use for my given ceiling span. I've found several calculators, but am unsure what load value to use.

Looking at a ceiling with two layers of 5/8 DW with Green Glue. The ceiling weight is entirely supported by the new constructed walls with no additional weight on top, so I'm thinking 0 live load. What would be the recommended dead load value I should use? How about if I add a layer of plywood or OSB in addition to the 2 layers of DW and Green Glue?

Many Thanks.

[Rod Gervais]

Kenny,

You don't say where you're located - however - if you're here in the us - then 0 psf live load is not allowed - this even though you might think this to be illogical....

For example - in Oregon, a ceiling without storage requires a minimum live load capacity of 10psf. The required load capacity is generally State specific..

As far as the dead load goes - you have to calculate all of the load being carried by the joist - this includes the weight of the ceiling joist - any stiffeners required due to the span of the members - all of the OSB/drywall being installed - any lighting - HVAC duct - etc, although for specific items located in specific areas - thus imparting loads to members that would not be carried by other members - you can calculate the loads for those specific members - while applying the general loads to the remainder of the members.

It is not necessarily as easy as one simple "this covers all" when you start getting into specialized ceiling design.......

Rod

[Screaminlove]

Rod,
do you think I could use this type of assembly (as drawn on the attached pdf)? This refer to figure 4.24, p.81. It seems like an effective and easy way to acheive both goals (sound and fire safe), when it's possible to use risc-1.
I ordered my clips, they should arrive next week, and I would love to know your thoughts about that before mounting the structure.

Thanks a lot!

[Kenny M]

Originally Posted by Rod Gervais

Kenny,

You don't say where you're located - however - if you're here in the us - then 0 psf live load is not allowed - this even though you might think this to be illogical....

For example - in Oregon, a ceiling without storage requires a minimum live load capacity of 10psf. The required load capacity is generally State specific..

As far as the dead load goes - you have to calculate all of the load being carried by the joist - this includes the weight of the ceiling joist - any stiffeners required due to the span of the members - all of the OSB/drywall being installed - any lighting - HVAC duct - etc, although for specific items located in specific areas - thus imparting loads to members that would not be carried by other members - you can calculate the loads for those specific members - while applying the general loads to the remainder of the members.

It is not necessarily as easy as one simple "this covers all" when you start getting into specialized ceiling design.......

Rod

Thanks Rod. All makes sense. I generally overbuild slightly requirement wise just to be on the safe side. I've got a span of about 12 to 14 feet (the one wall is angled) and would like to stick with 2x6 joists if possible just to not lose a couple inches of ceiling height. That would work with a 12 foot span, but I'm right on the verge of not working as the room widens out. This makes it more critical to calculate the load as I'm most likely pushing it with 2x6's. I'm down here in Los Angeles btw.

So looks like a sheet of 5/8 DW weighs about 2.2 lbs/SF
1/2" OSB weighs 1.66 lbs/ SF

Not sure about the weight of 2x6 or 2x8 joists yet and the ceiling clouds with small can lighting I make aren't very heavy. Also no duct work and minimal AC so I'd think a 10lb/SF load would be good for my calculations. Does that sound about right?

Thanks.

[GreenNeedle]

Originally Posted by GreenNeedle

Attachment 310480

Rod, what is your method of getting the compressed rockwool in the space between he wall and jam?
Can we just use low expanding foam and still backer rod and caulk the edge?

Hi again, sorry to be on about this but i can't get my head around using foam in the shimmed space around the door. It's so light weight, doesn't it create a week point in the wall system?
There is an inch around the perimeter of each door, if i foam it and case it and caulk the casing is that enough???

[Rod Gervais]

Originally Posted by GreenNeedle

Hi again, sorry to be on about this but i can't get my head around using foam in the shimmed space around the door. It's so light weight, doesn't it create a week point in the wall system?
There is an inch around the perimeter of each door, if i foam it and case it and caulk the casing is that enough???

Don't feel bad - I can't get my head around it either - I opt for thermafiber because it's a dense material - as such it holds with the entire concept of mass isolation systems - standard expansive foam is much too lightweight.

Now - they do make some very dense expansive foams, some in densities matching that of the thermafiber when all is said and done - although it becomes important that these then must also be slow expanding in nature because the can blow the jamb if they expand too fast with that much density.

They are also very expensive and are not available in the small cans that you think of when you picture expansion foams. You will not find these products in Home Despot.

As far as how to pack the jambs - simply use a putty knife or a thin piece of wood to pack the material in - if you have split jambs it's quite easy to place a temporary stop in the space between the jams to pack against.

The other problem with the expansive foam is the fact that it is a pain in the butt to trim back far enough to install backer rod and caulk after the product sets up.

Rod

[RJHollins]

For the split jamb area, I'm considering an initial insert of backer rod. Then using puddy pads, like we used to seal electrical boxes, formed into long rolls and inserted into space.
We could then 'finish' with a layer of silicon caulking.

Thoughts?
Thx

[Rod Gervais]

Originally Posted by RJHollins

For the split jamb area, I'm considering an initial insert of backer rod. Then using puddy pads, like we used to seal electrical boxes, formed into long rolls and inserted into space.
We could then 'finish' with a layer of silicon caulking.

Thoughts?
Thx

Not a clue - the putty pads only have value if they are firmly embedded into the surrounding material - they do add mass however this is not their intended use - and I have no idea how the oils in the putty pads might react with any particular caulking material over the years.

It's not an experiment I would choose to invest in when there are methods for reaching the goal that are time tested and proven...... why reinvent the wheel when it's rolling perfectly as is?

There is also the fact that this is going to be a much more expensive approach than approaches we use that we know work for sure.

You can take your chances and let us know in 5 or 6 years how it worked out long term if you wish.

Rod

[GreenNeedle]

Originally Posted by Rod Gervais

Don't feel bad - I can't get my head around it either - I opt for thermafiber because it's a dense material - as such it holds with the entire concept of mass isolation systems - standard expansive foam is much too lightweight.

Now - they do make some very dense expansive foams, some in densities matching that of the thermafiber when all is said and done - although it becomes important that these then must also be slow expanding in nature because the can blow the jamb if they expand too fast with that much density.

They are also very expensive and are not available in the small cans that you think of when you picture expansion foams. You will not find these products in Home Despot.

As far as how to pack the jambs - simply use a putty knife or a thin piece of wood to pack the material in - if you have split jambs it's quite easy to place a temporary stop in the space between the jams to pack against.

The other problem with the expansive foam is the fact that it is a pain in the butt to trim back far enough to install backer rod and caulk after the product sets up.

Rod

Ok so i pack in the mineral wool in and stick backer rod at the edge and caulk the 1 inch space with Acoustic caulking before putting on the casing? That's lots of Caulk.
Could i not just attach the casing and make that air tight with the caulking?
Seems neater.

[Rod Gervais]

Do as you wish - this seems what you want - so go for it. I make recommendations based on what is now 40 years in the industry - if you want to take a short cut it doesn't affect me in any way.

[GreenNeedle]

Originally Posted by Rod Gervais

Do as you wish - this seems what you want - so go for it. I make recommendations based on what is now 40 years in the industry - if you want to take a short cut it doesn't affect me in any way.

I don't want to take a short cut but i have 11 doors to do and i don't want to do superfluous caulking. If i need to do it at the jam joint i can and will. Just wanted confirmation. Thank you.

[Rod Gervais]

A 1" space around a frame is excessive - it should not be more than 1/2" - - so if you have not hung the doors yet correct the framing - if you have already hung the doors you are going to have to live with that - but then I would not use acoustic caulk for the opening - I would use Big Stretch.

I don't know of an acoustic caulk that is designed for an opening that wide:

This from USG on their SHEETROCK® Brand Acoustical Sealant:

Use a caulking-type gun. Apply 1/4
minimum round bead of sealant (1/2
maximum) to seal perimeter of soundrated partition. Seal sound-rated partitions on both sides where facings abut dissimilar materials: around perimeter, in the angle formed by panels and abutting dissimilar materials; at all intersections; at all panel terminations in door and window frames; and at control joint locations before attaching the control joint to the panels. Apply continuous beads of sealant around all openings formed for outlets, lights, etc. Completely butter the outside of electrical boxes. Cut gypsum panels with 1/8
maximum relief at perimeter to receive sealant. Install before sealant skins.

Rod

[xaMdaM]

Rod,

Forgive me for butting in on this thread... Green Needle, I hear ya' about the amount of caulk on those 11 doors, but you've come too far not to finish it correctly... as you said.

I had one door that the framing::door frame gap was right at 1" wide on the latch side. I ended up cutting the nails out with a sawzall and managed to get a piece of 3/4" pine stock in that gap, and re-nailed the door frame in place. Thus, making the caulk and backer rod placement much easier to do.

As a side note, IIRC, I think I used somewhere in the neighborhood of 1 tube of SC175 per door for a total of 7 doors/frames. My total caulk use was something on the order of 12 cases of the large tubes and 3 cases of small tubes in a 1680 sq ft studio. Acoustic caulk is similar to nails and fasteners... a bit of a hidden cost that becomes real money.

[Rod Gervais]

Originally Posted by xaMdaM

Rod,

Forgive me for butting in on this thread...

Max,

Nothing to forgive my friend..... feel free to jump in as you might choose.

Rod

[GreenNeedle]

Thanks Guys.
And Rod thanks for the tip on the Big stretch, i'll look into getting some.
Btw i only have 3 frames installed so we will re-visit our methods to get closer to 1/2 inch spaces.

[Rod Gervais]

Originally Posted by Screaminlove

Rod,
do you think I could use this type of assembly (as drawn on the attached pdf)? This refer to figure 4.24, p.81. It seems like an effective and easy way to acheive both goals (sound and fire safe), when it's possible to use risc-1.
I ordered my clips, they should arrive next week, and I would love to know your thoughts about that before mounting the structure.

Thanks a lot!

Screaming - no that will not work - what this will do is stop the ceiling from being able to move freely - which is one of the critical aspects for any of the resilient or RISC systems to work.

What you need to do in your case would be much more like Figure 10.12 - which allows the floor joist the ability to move without touching the wall yet locks the wall in laterally.

Rod