Basement home studio - concrete, flanking and door selection

[Gregwor]

Here are the latest sketches:

2 things.

1. Do a quick Google search to see the industry standard for framing door rough openings. Your trimmer stud and header needs adjustment. I also don't think you need to sister up the cripples.

2. I would use 3 single noggins in the first stud bay rather than 2 sistered noggins.

thinking about moving the door to make more space for a radiator, also thinking smaller doors

Remember, if you use a bank vault style sealing system on your door, that's 2 layers of sealing... let's just say they are even 1/2" for each seal, that means you have 1" eaten up on each side of the door. So, your opening will be 2" narrower. For 4731 seals, I believe those are 3/4" each. So your door ends up being at least 3" more narrow. For that reason alone I recommend building your doors out of 3 foot wide slabs.

- duct boxes size, position and support - my first versions are a bit bigger than necessary. When they are a bit smaller I think the outer boxes will just fit between the leaves. I'm not going to redesign the exact positions until I break open the legacy stud wall and check exactly where/how the legacy ducting runs behind the wall.

Your rough positioning of the boxes is not ideal in that the air flow won't really circulate the entire room. Chances are the air will take the shortest path and just rip from the one to the other. Ideally you want supply on one end of your room and the return on the other end. If that's not possible, place them as far apart as you can.

I understand the general concept but TBH I'm lost with Greg's diagram compared to Rod's sizing.

A quick glance at Rod's design for that guy shows me that he is introducing several cross sectional area (let's refer to that as CSA) changes throughout the box. There are pros and cons to his design.

Initially his inlet does not introduce a CSA change. Instead the change is made via the baffles, making the CSA smaller. The issue with this is that it adds a lot of static pressure. Put 4 of these boxes in your room and you've introduced a buttload of static pressure.

Check this thread: I posted a static pressure calculator on it (there might be a fancier version on it's way in the near future )
http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21752

Typically, you want the CSA within the box to be as big as possible. This allows for less static pressure, more insulation for better insertion loss. If your system can handle the extra static pressure, feel free to make some smaller CSA portions in the box. Remember, for better insertion loss, the greater the CSA change, the better. Check these out for reference:

Insertion Loss Graph from Engineering Acoustics 2009.png

Silencer Box Lining Thickness Attenuation.png

Insertion Loss Expansion Chambers from Engineering Acoustic 2009.png

Duct Size With Duct Liner Attenuation.png

As you can see, it is a trade off. The larger the CSA change, the better. But, the bigger the CSA, the thicker the duct liner should be. So, what I'm getting at is that you should have at LEAST 2 times the CSA inside your box than the duct that is feeding it. If you can have more static pressure, shrink the CSA in the box (at some point... let's just say at the middle baffle) to half the CSA of your duct that is feeding the silencer. That way, you have a CSA ratio change of 4. This all depends on your total static pressure of your system and whether or not your fan can handle it.

This diagram is a great way to try and get this across but TBH I just don't get it yet! I'll try again

Typically people are doing their best to find a place to fit a silencer box. Often people only have 10 or 12" to fit one in. My little design guide image there allows for a quick way to figure out the biggest CSA possible while fitting into these tight spots. If you need more guidance with it, let me know.

Vapour barrier - as in the last post, do I need one

For your climate and the fact that it is an exterior wall, I believe you do need it.

how does it work where I have the transition between inner leaf that is opposite an internal wall, and inner leaf that is opposite an external all

This is always so hard to explain.. I really just need to draw up a diagram already.

The basic rule of thumb is to have your barrier on the cavity side of your inner leaf sheathing... no different than a typical home build where a basement frost wall is covered with barrier and then drywall is installed directly on top of the barrier. The transitional spot between the rest of your house and your sound room, you can just place the barrier to span the gap between the two. This cavity will be filled entirely with insulation.

Unless someone can correct me on this, that is how I believe it should be done. Barrier and the fear of mold is a scary subject and it's awesome that you're actually trying to deal with it properly!

Greg

[mc_deli]

Greg

Brilliant, thanks for the reply again.

Doorway: roger that. I'll make some edits to the framing and find out the standard mm sizing for things here. Note: I am not considering "bank vault" style doors at this point. I am looking at a a pair of off-the-shelf Jeld-Wen 810s and closing mechanisms. Locally doors are typically supplied with a one piece jamb and stop (I think this is the correct terminology) already cut. So, the "rough" door opening size is designed for that (hence my current SketchUp has the 890 x 2090 mm opening as spec'd by Jeld-Wen. There's a decision to be made here. I can go the "Finnish way" and use the out-of-the-box doors and surround - or I can beef up the doors and make the surrounds from scratch. I think I would prefer the O-o-t-B for simplicity, resale and minimize risk of user error... but it has to get me 55dB, so I need to check some more.

Duct boxes positioning: Yes, not ideal is it! At the moment, in the legacy room, the in/out air vents are 46cm apart! So, I figured I already have scored a major victory in getting them 181cm apart (as shown in the SketchUp diagram above). Because of the shape of the room and the sliding doors across the West side, I think this is the best I can do. The reason the vents are so close together now is that they come through in a narrow false ceiling outside this room.

Duct boxes size: Wow. That's a lot to take in. I'll try to grasp it and refine the design. Thank you for posting that.

Vapour barrier: I have to find out more about this. I've found (and lost!) and G****lutz post with Rod about a vapour barrier construction where exterior outer leaf meets interior outer leaf. I am wondering if I have a way of circulating air in the gap between inner and outer leaf (I plan two parallel doors so is there a way there - or a way to take air from the outer leaf duct boxes into the "gap"???).

Greg, this was interesting:
"The basic rule of thumb is to have your barrier on the cavity side of your inner leaf sheathing... no different than a typical home build where a basement frost wall is covered with barrier and then drywall is installed directly on top of the barrier. The transitional spot between the rest of your house and your sound room, you can just place the barrier to span the gap between the two. This cavity will be filled entirely with insulation."

I understand that the vapour barrier should be between inner leaf drywall and inner leaf stud. OK. And then, where an exterior wall meets an interior wall, the vapour barrier should span the gap from inner leaf to outer leaf.

Today's question then
However, I understood that I should not add insulation to exterior outer leaf walls (presumably to leave room for air circulation and avoid trapping moisture (or worse))... or did I get my wires crossed?


Good news - advice incoming
I've had constructive conversations with local acousticians and special thanks to Steve from Mason for explaining sway bracing in detail.
I've looked at the local guidance on noise, residential noise, excessive noise etc. and AFAIK I don't have any issues and I don't need any special permissions, I just have to make sure the build is to "code" and that the plan is scrutinized by a suitably qualified professional i.e. structural engineer.
I also have a couple of candidate engineers, who I understand will advise on e.g. vapour barrier as well as load bearing.
And I have a better selection of local vendors (there is a local importer for AMC Mecanocaucho, and one local vendor has a special on 18mm drywall (ooh!)).

However, I can't buy anything yet... I think the order this will go: I need to get the engineer's feedback, tweak the plan a bit, give my building's chief a heads up and then I can get the engineer to do some kind of work/report.

To do list for my own benefit;)

- pipe box access - 45 degree frame in NE corner
- doors detail - resize and re-frame, research out-of-the-box surrounds
- window detail - research out-of-the-box window options
- framing to support electrical/radiator/treatment - edit/add framing to be ready for all the inner leaf elements.
- framing to support the cloud - solution for this (is anchoring the drywall enough)
- duct boxes size, position and support - yeah, as above

- duct box material - MDF just isn't a thing here (presumably sales curtailed due to health risk?) so I need an alternative material. Birch ply apparently is one - but €€€€ kerching. Also I need to contact some local HVAC companies to see where they get their duct liner from

- sway bracing - work out which of wall ties and/or ceiling ties are needed for which wall, choose between wall ties e.g. (Mason DNSB-A or AMC EP600 and ceiling anchor solution e.g. Mason AB-716 or AMC EP 500

- Ceiling clips/channel - choose between just resilient channel (Gyproc AP25 = cheap, local), Mason AFA clips (imported and local furring channel, or Reducto clips/channel imported from the very helpful people here. I am presuming that the AFA or Reducto clips will be much easier to work with than resilient channel and minimize the risk of user error. Comparison data between AFA vs Reducto (or vs Genie) is not available AFAIK. The Reductos look great and I think those with locally sourced furring channels makes sense price vs performance-wise in this case.

- Floor - more mass for the floor based on friendly local advice, so I will change it to Paroc SSB 2t, 2x 15mm Gyproc GL flooring drywall, 6mm MLV, 22mm tongue and groove particle board, and then laminate. I'll lose a bit of height there (an extra 21mm but I think I should swallow that).

- Vapour barrier / air circulation in between the leaves - solution and plan needed. Argh.

...No one said it was easy!

[Gregwor]

but it has to get me 55dB, so I need to check some more.

If you are using a single door, to get the best isolation, you should use a home made "super door". Check it out in this PDF:

Building Studio Doors.pdf

I am wondering if I have a way of circulating air in the gap between inner and outer leaf

I can't see a way for any air to circulate in that cavity.

(I plan two parallel doors so is there a way there - or a way to take air from the outer leaf duct boxes into the "gap"???).

I can't read that link to your potential door. If it's a metal door, that will mean you have a 4 leaf door system which is not good.

Regarding air in the gap, you shouldn't have any voids in there. The entire cavity should be full of insulation. -- other than a small gap at your foundation which as far as I know is code --> see the next comment.

However, I understood that I should not add insulation to exterior outer leaf walls (presumably to leave room for air circulation and avoid trapping moisture (or worse))... or did I get my wires crossed?

Correct.

framing to support the cloud - solution for this (is anchoring the drywall enough)

Don't trust drywall anchoring for something that could fall on someones head. You'd have to anchor into the hat. I could be out to lunch here but from what I remember, clips and hat are rated to hold roughly two layers of drywall. Clouds get heavy so that concerns me. You might have to build your cloud out of light tin or something like that to reduce weight.

MDF just isn't a thing here (presumably sales curtailed due to health risk?) so I need an alternative material.

OSB is pretty cheap. It just needs to be thicker in order to match the surface density of MDF. Here is one made of OSB. You can see that two layers of ~3/4" OSB was used:

Frank Y Silencer Box.jpg

Greg

[mc_deli]

Greg, you rock, thanks!

but it has to get me 55dB, so I need to check some more.

If you are using a single door, to get the best isolation, you should use a home made "super door".
Greg

No, sorry for the confusion. I am looking at 2x parallel Jeld-Wen Fire 810 doors rated at 38dB.
AFAIK these are wood laminate and supplied with lock frame, wood frame, seals, triple hinges, sill with seals.
I think it's fair to say that standardisation is very common in lots of areas in Finland. Connected with that it means that if I choose the 9 x 21M version, then my "rough frame" should have dimensions of 890 x 2090 mm and the door is 825 x 2040 mm.
Of course, it's possible the seals will need to be upgraded. I'll check with the door guy;)
Overall, for resale, to avoid user error and simplify, I like these as an "out-of-the-box" solution.

Here's a G**** translate of the original:

Screenshot 2020-02-11 at 14.08.15.png

On everything else you mentioned, yes, agreed and taken on board


Today's question is about a rethink on the ceiling, should I use metal studs
At the moment I have a design with no ceiling joists, because I understood I would need at least 200mm joists for my 3.5m span. The knock on effects of this are: cost of acoustic clips and channel for decoupled ceiling, problems hanging a cloud, cost and complication of sway bracing and ceiling anchors for the inner leaf walls to stop them moving... so am I missing something... should I actually use metal studs for the ceiling...?

My ceiling is so... er... modest... the LVL wall framing is presumably super solid and able to bear a lightweight channel (EDIT: I think I am looking for a "low profile @20 gauge structural steel stud, but I can't find it!), metal stud could be much lower profile than wood joist... trying to find span tables now... is this a good idea?

[Gregwor]

AFAIK these are wood laminate and supplied with lock frame, wood frame, seals, triple hinges, sill with seals.

My ceiling is so... er... modest... the LVL wall framing is presumably super solid and able to bear a lightweight channel (EDIT: I think I am looking for a "low profile @20 gauge structural steel stud, but I can't find it!), metal stud could be much lower profile than wood joist... trying to find span tables now... is this a good idea?

It all depends on the span tables. I can't see thin steel like that being very strong though.

Greg

[mc_deli]

AFAIK these are wood laminate and supplied with lock frame, wood frame, seals, triple hinges, sill with seals.

My ceiling is so... er... modest... the LVL wall framing is presumably super solid and able to bear a lightweight channel (EDIT: I think I am looking for a "low profile @20 gauge structural steel stud, but I can't find it!), metal stud could be much lower profile than wood joist... trying to find span tables now... is this a good idea?

It all depends on the span tables. I can't see thin steel like that being very strong though.

Greg

Steel stud
I can't find anything steel suitable so I'll drop that and stick with clips/channel (specifically AMC EP 700+ clips and Gyproc GK channel).


Status
My status is that I have now selected all the key materials for this, including e.g. wall ties/sway bracing, and I am in the process of updating all my documents for the structural engineer.

However, I have a new WTF SNAFU.

Frequency specific flanking/STL
I was just talking to my neighbour about what I've got planned and we did a quick STL test. I quickly put on a track at 85 dB (slow C weighted) and we heard nothing in his place the other side of the firewall. I upped it to 95 dB and all we could hear was some vocal and not enough to tickle my meter, suggesting well over 60dB of STL from the firewall. Totally different from previous results.

This makes me think that the STL between our apartments is very very frequency specific.

And there is no way I should proceed with this without frequency-specific STL measurements. I could quite easily (do this for 6 weeks and spend 8k and) get this wrong and amplify the biggest problem frequency while having no discernible effect on 99% of the rest of the frequency spectrum.

Need to measure
So, I think I need a more sophisticated methodology for measuring STL across the full frequency spectrum. And I don't think I should continue before doing it because I am now doubting the whole project!

I have Sonarworks with their mic, which I think is a good candidate for a measurement mic. I have test CD content with frequency sweeps. But...

What's weird is, on here, or on GS, I cannot find a methodology for this - am I missing something...

Question:
- What is a good/standard/DIY measurement methodology for measuring STL between structures across the whole frequency spectrum?

(EDIT: Looking at REW, found the Sonarworks mic calibration file, realise I need 1/3 octave measuring... still unsure if REW can do this or how to do this...)

(EDIT again: this question has been pretty well answered here on the REW forum. Basically I need to get my Sonarworks mic calibration file into REW, fire up a sweep, measure multiple times in the sending room and receiving room, at high SPL i.e. +100dB, and then average the results and come up with the differences. Let's see how quickly I can get that together;))