# Which code applies, IRC or IBC?



## stillmand (May 12, 2022)

This duplex was built last year. The builder says that the applicable code is IRC. But my understanding is that IRC doesn’t apply to buildings more than 3 stories. And to me this is more than 3 stories (see picture: 



https://imgur.com/a/yZTCERq

), which means that IBC is the required code. Note that the loft level is a livable space with a finished floor, bathroom, etc.

Would love any feedback on this.

Again, here is the picture: 



https://imgur.com/a/yZTCERq


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## bill1952 (May 12, 2022)

I think this may apply:

*R325.6 Habitable Attic*

A habitable attic shall not be considered a story where complying with all of the following requirements:

The occupiable floor area is not less than 70 square feet (17 m2), in accordance with Section R304.
The occupiable floor area has a ceiling height in accordance with Section R305.
The occupiable space is enclosed by the roof assembly above, knee walls (if applicable) on the sides and the floor-ceiling assembly below.
The floor of the occupiable space shall not extend beyond the exterior walls of the floor below.


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## tbz (May 12, 2022)

Looks to comply with designing and building under the IRC 1 and 2 family dwelling code, with the little information provided. 

My question is why are you asking what code after the project was built?

Are you questioning the Architect that drew it, noted the right code requirements
The builder submitted the wrong application for permit and;
That the Plan reviewer and building department missed the correct code on application
No offense but the question seems to be fishy with the amount of eyes and hands that had a part of the process before, during and up to the final certificate of occupancy was issued.

from where I am sitting on my chair anyway....


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## mtlogcabin (May 12, 2022)

IBC for structural part of the structure. The columns supporting about 2/3rds of the structure are way beyond the IRC prescriptive requirements

R301.1.3 Engineered design.
Where a building of otherwise conventional construction contains structural elements exceeding the limits of Section R301 or otherwise not conforming to this code, these elements shall be designed in accordance with accepted engineering practice. The extent of such design need only demonstrate compliance of nonconventional elements with other applicable provisions and shall be compatible with the performance of the conventional framed system. *Engineered design in accordance with the International Building Code is permitted for buildings and structures, and parts thereof, included in the scope of this code.*


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## stillmand (May 12, 2022)

tbz said:


> Looks to comply with designing and building under the IRC 1 and 2 family dwelling code, with the little information provided.
> 
> My question is why are you asking what code after the project was built?
> 
> ...


Thanks so much, happy to give a little more background. 


tbz said:


> Looks to comply with designing and building under the IRC 1 and 2 family dwelling code, with the little information provided.
> 
> My question is why are you asking what code after the project was built?
> 
> ...


Thanks for the answer and happy to provide more background. Blueprints called for “2-hour firewall” with 2 layers of 5/8” drywall on each side of the common wall. But in reality they only put in one layer on each side. Builder now claims that they really only had to meet a 1 hour firewall because they say building falls under IRC rather than IBC.

There is also no sound protection across the common wall. STC is in the 30s. Builder is willing to address but the question is whether they need to meet an IRC requirement of STC 45 or IBC requirement of STC 50. 

This is in Ocean City, Md. The code and various ordinances are hard to decipher as to what is the true fire code and sound transmission code for this structure.


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## Jay Smith (May 12, 2022)

The extra layer of gypsum board on each side sounds like the way to achieve the STC.


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## tbz (May 13, 2022)

STC numbers are not the best judge of an end result.  I have been working through an old row home/ town home noise issue for about a year now.

I would be more interested in correcting the specific issue you have or goal than achieving a certain STC number.  

The Town home I am working with was built in 1875, common wall is a single old school 2x4 turned on its face, so 1.75" thick.  I went with 1.5" Safe & Sound and then Mass loaded vinyl barrier and two layers of 5/8" wall board.  Since the neighbor is not into improving their side, I am only halfway to a reasonable level.  I was not able to add another wall on the second floor because of the stair flight was on that wall, takes up 14 feet and there was no way to move it on a 12x28 floor plan. 

I did however add a 2x4 gapped wall with staggered studs on the first floor, except on the stairwell going to the second floor level.  

This with the 1.5" of safe and sound in the original common wall and then 3.5" of safe and sound in the new offset wall with the Mass loaded Vinyl and 2 layers of 5/8" wall board, has been a huge difference.  But the lower base levels and the high pitches seem to just bleed through.

To really solve the issue, you will have to spend a good bit more than the code or the builder is responsible for.

Just getting to a higher STC is not really going to change what you personally have an issue with currently.

I could be wrong, but I would take a real hard look at it before just achieving a specific STC.

Good luck


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## Joe.B (May 13, 2022)

So built last year, as in it's complete? Find the approved (stamped) construction plans and see what they show. If the plans were approved as it was built I don't think anything's going to happen. If the buildings were not built to plan then you might have some leverage.


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## stillmand (May 13, 2022)

Joe.B said:


> So built last year, as in it's complete? Find the approved (stamped) construction plans and see what they show. If the plans were approved as it was built I don't think anything's going to happen. If the buildings were not built to plan then you might have some leverage.


Thanks Joe, yes that’s right. It is complete. The blueprints on file with the city show 2 layers of drywall on each side of the common wall. But in reality only one layer was installed on each side.


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## stillmand (May 13, 2022)

tbz said:


> STC numbers are not the best judge of an end result.  I have been working through an old row home/ town home noise issue for about a year now.
> 
> I would be more interested in correcting the specific issue you have or goal than achieving a certain STC number.
> 
> ...


Thanks so much for this reply. Would be interested in any additional feedback. The situation is this. We can hear every word our neighbor says and they can every word we say with barely a raised voice. 

While agree it’s the solution not the STC that matters, the fact is the matter is that based on how easy it is to have a conversation across the wall, the STC is somewhere in the low to mid 30s. The code requires an STC of 45, which would be a major improvement. Not perfect, and we’re not going for perfect, we (us and the neighbors) don’t think it’s acceptable for new construction that we can easily hear each other’s conversations, let alone kids screaming and dogs barking.

Again I agree it’s the solution that matters, but the builder is only going to feel obligated to meet the code required STC of 45. We can always offer to cover the cost of going above and beyond that value if we want to.

One thing I was thinking (and we’re working together with the neighbors by the way) is let’s say the builder agrees to add an additional layer of drywall on one side of the wall, and that they claim that will get us to STC 45. Could we then decide on our own to add an additional layer on the other side in targeted areas, say the master bedroom wall (the units are mirrors of each other), or the main level wall but not the adjoining staircase (since it is a lot more complicated and expensive to deal with stairwell walls), to add extra protection in those targeted areas. Or do have to the same to the whole wall to get any benefit due to flanking.

It sounds like from your description maybe you had done success treating one span of the wall but not the continuation of the wall into the stairwell? (Our stairwells are open, not enclosed)


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## Joe.B (May 13, 2022)

The reason I was asking about the approved plans is they function as a contract. If the plans show two layers on each side and they only installed one then they did not build what was approved, regardless of whether they claim to "meet code". Even if what they built did meet code minimum standards it was not what was contracted to be built. Normally this should have been caught by inspections, and even if not the customer (the one paying the contractor) did not get what was agreed upon and they are the ones who have been "cheated." If you are the one who paid for this to be built then you may have a reasonable claim against the contractor.

Based on the tone of this thread I suspect that the one paying the bills was trying to pinch every penny and cut the corners by saying "well it only needs one layer by code so why should we pay for two?" or even worse (and maybe more likely) the builder is the owner. If this is the case and you're the tenant then you are in for an uphill battle.

If the property owners are willing to do a little work to try to make you a little more comfortable then a second layer of drywall will help. A layer of soundboard in-between the two layers of drywall will help a little bit more. There's a product out there called "Green Glue" that is designed to go between two layers of drywall and I've heard first hand accounts that it actually works really well. Here's a link if you want to check that out:






						Noiseproofing Compound
					

Noiseproofing Compound  Fast, simple, and effect are the best descriptors of Green Glue Noiseproofing Compound. Green Glue Noiseproofing Compound is a unique damping product that is ideal for new construction and renovation projects. As the most cost-effective soundproofing material on the...




					www.greengluecompany.com
				




Good luck and let us know how it goes.


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## tbz (May 13, 2022)

The green glue with another layer of 5/8" will reduce the noise level, but it will not solve it to the level you would be happy with if the clarity of the speak is that clear in my opinion.

Without knowing the exact wall insulation / sound proofing between the 2 units, and truly knowing if it is gapped double wall or if it is a single wall with 2 layers of 5/8" drywall, one on each side you can't even begin to comprehend how well sound travels through a floor system.  The place I am in is one single deck with the 5/4 x 6 floorboards (construction today uses plywood) running from the unit next to me into my unit.  Next door they just refinished the 145 year old floors, and I did the same, when you drop something on the floor like a quarter, sounds just like it was in the same room.  

I hate carpet, so I installed a padding with an engineered flooring on top, the difference in massive, another reason people like carpeting for the sound deadening.

But sound will also travel through the wood studs, thus gapping and breaking the bridge is important.  All the times I have used Green glue, it worked ok for the mid tones, but nothing on lower base tones and some higher tones, thus you still heard everything, just not so precise.  

I got my best results with gapping and safe and sound from rockwool, and then the Mass loaded vinyl barrier before sheet rock, the Mass loaded vinyl barrier breaks the path of travel from the wood and dulls the sound passing through the voids (insulation zones) besides the wood studs, then 2 layers of drywall.

If the sound is that clear with a STC of 30, getting to 45 might be an improvement, but the STC is mainly the mid tones, so the highs and low are normally still pretty clear when sitting near the wall or rooms without carpeting.

That is what happens when your neighbors are that close and the architectural plans are figured for the basic minimums.  

Not sure what your options are, but I would look at all of them before pulling the trigger and not being afraid to try and work out getting a better level for more money, I have never been happy with STC 45 levels.

Then again I like it quite.....


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## bill1952 (May 13, 2022)

I've spent 40+ years as a consultant on design of performing arts facilities and noise isolation was always a key part.

Look for flanking paths.  No doors or other such openings, basement floor to roof. As I understand the code, that sheetrock should be continuous, not just floor to ceiling. And to  roof deck and exterior sheathing. If two layers, that too. So try to figure out if the did that. No back to back electrical openings, at least a stud bay away.  For sound, they should have been sealed with acoustic (butyl) caulk.  Ditto any pipe penetrations and actually no ducts or pipes passing through wall (for acoustical).  After all those paths are stopped, if the wall is not insulated, I'd blow cellulose into each cavity. Without flanking paths, drywall on both sides with cellulose does a pretty good job empirically.

If adding drywall, not sure it meets fire resistance but putting it on resilient channels and acoustic sealant at edges will get a lot of isolation. Use 5/8 if possible. Lot of work resetting trim, electrical, etc., but it will be major improvement. I don't know how well the green stuff does what the resilient channels do. 

The acoustical consultants I worked with - the top firms in US -  all just about dismissed the leaded vinyl material. It's heavily marketed and costly, much more costly than drywall or plaster pound for pound - and mass is a key. YMMV.


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## Jay Smith (May 13, 2022)

Perhaps a little hard to believe, but the GenieClip RST retrofit assembly is claimed to provide an improvement of 12-18 dB.



			https://pliteq.com/products/sound-control-clip/genieclip-rst/


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## bill1952 (May 13, 2022)

Resilient channels and similar are effective. Loading them up can even improve them. One acoustical consultant I worked with a lot did this on his grandson's room - gluing scraps of gwb to the back of the panels to be mounted on the channels, between channels.


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## Genduct (May 13, 2022)

stillmand said:


> Thanks so much, happy to give a little more background.
> 
> Thanks for the answer and happy to provide more background. Blueprints called for “2-hour firewall” with 2 layers of 5/8” drywall on each side of the common wall. But in reality they only put in one layer on each side. Builder now claims that they really only had to meet a 1 hour firewall because they say building falls under IRC rather than IBC.
> 
> ...


"This is in Ocean City, Md."
Before I read this, the design seemed to me to be a Shore Home.
At the end of the day, I think you need to approach these kinds of questions in the light of INTENT and Not look for little pieces of Code to hang your Hat On

So, the lower level ENTRANCE area could be considered Habitable area, but in the context of the Shore Home, it is not really just and enclosed Porch ?  ( that could get flooded)

So with that in mind, would that kind of thinking not better way  to the approach the question


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## stillmand (May 13, 2022)

tbz said:


> The green glue with another layer of 5/8" will reduce the noise level, but it will not solve it to the level you would be happy with if the clarity of the speak is that clear in my opinion.
> 
> Without knowing the exact wall insulation / sound proofing between the 2 units, and truly knowing if it is gapped double wall or if it is a single wall with 2 layers of 5/8" drywall, one on each side you can't even begin to comprehend how well sound travels through a floor system.  The place I am in is one single deck with the 5/4 x 6 floorboards (construction today uses plywood) running from the unit next to me into my unit.  Next door they just refinished the 145 year old floors, and I did the same, when you drop something on the floor like a quarter, sounds just like it was in the same room.
> 
> ...


Thanks you, these are great insights. The common wall is single


tbz said:


> The green glue with another layer of 5/8" will reduce the noise level, but it will not solve it to the level you would be happy with if the clarity of the speak is that clear in my opinion.
> 
> Without knowing the exact wall insulation / sound proofing between the 2 units, and truly knowing if it is gapped double wall or if it is a single wall with 2 layers of 5/8" drywall, one on each side you can't even begin to comprehend how well sound travels through a floor system.  The place I am in is one single deck with the 5/4 x 6 floorboards (construction today uses plywood) running from the unit next to me into my unit.  Next door they just refinished the 145 year old floors, and I did the same, when you drop something on the floor like a quarter, sounds just like it was in the same room.
> 
> ...


thank you for these insights. The common wall is a single wall 2x6 wood studs, 16” OC, with 5.5 inch fiberglass batts (yes, a terrible acoustic design). Let’s say we add an extra layer of 5/8” drywall to one side of the all for the whole common wall, except for the master bedroom to master bedroom wall, where for more privacy we decide to spend the money to tear down the existing wall and put up a new one with resilient channel or isolation clips for decoupling. Will that have the intended impact of providing an extra meaningful reduction in sound across the master bedroom wall compared to the rest of the house?


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## stillmand (May 14, 2022)

bill1952 said:


> I've spent 40+ years as a consultant on design of performing arts facilities and noise isolation was always a key part.
> 
> Look for flanking paths.  No doors or other such openings, basement floor to roof. As I understand the code, that sheetrock should be continuous, not just floor to ceiling. And to  roof deck and exterior sheathing. If two layers, that too. So try to figure out if the did that. No back to back electrical openings, at least a stud bay away.  For sound, they should have been sealed with acoustic (butyl) caulk.  Ditto any pipe penetrations and actually no ducts or pipes passing through wall (for acoustical).  After all those paths are stopped, if the wall is not insulated, I'd blow cellulose into each cavity. Without flanking paths, drywall on both sides with cellulose does a pretty good job empirically.
> 
> ...


Fabulous feedback, thank you. If you’re able to take a look at the blueprint and provide any more fine tuned advice based on it, I would be grateful. The one caveat being that while the blueprint shows 2 layers of drywall on each side of the common wall, in reality there is only one layer on each side. Here is the link. Sometimes you have to reload it a few times: 

http://weblink.ocgov.org/Weblink/ElectronicFile.aspx?docid=271878&dbid=0


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## bill1952 (May 14, 2022)

Didn't seem to work on my phone. I'll try to get to laptop this weekend.


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## tbz (May 14, 2022)

Though a great sound barrier, remember to take a good look at what you are planning to hang on a wall with resilient channels, if it is nothing more than pictures and some other things its a great choice, if you are planning on hanging any millwork, cabinets or entertainment systems, make sure to plan the mounting locations to support those items and sound proof them.

I can't say enough about ROCKWOOL Safe & Sound, if it is an option to remove and install new insulation between, I found it to be worth the cost.

Here is a demo video - 




This with the resilient channels and double drywall will drastically improve the current STC i would think.


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## Genduct (May 14, 2022)

stillmand said:


> Thanks you, these are great insights. The common wall is single
> 
> thank you for these insights. The common wall is a single wall 2x6 wood studs, 16” OC, with 5.5 inch fiberglass batts (yes, a terrible acoustic design). Let’s say we add an extra layer of 5/8” drywall to one side of the all for the whole common wall, except for the master bedroom to master bedroom wall, where for more privacy we decide to spend the money to tear down the existing wall and put up a new one with resilient channel or isolation clips for decoupling. Will that have the intended impact of providing an extra meaningful reduction in sound across the master bedroom wall compared to the rest of the house?


Since you are going to laminate another layer of gyp,  why not blow in some insulation then cover the holes?


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## stillmand (May 14, 2022)

tbz said:


> Though a great sound barrier, remember to take a good look at what you are planning to hang on a wall with resilient channels, if it is nothing more than pictures and some other things its a great choice, if you are planning on hanging any millwork, cabinets or entertainment systems, make sure to plan the mounting locations to support those items and sound proof them.
> 
> I can't say enough about ROCKWOOL Safe & Sound, if it is an option to remove and install new insulation between, I found it to be worth the cost.
> 
> ...


Thank you for this. I’m not an expert and honestly not very handy at all; so i don’t know exactly what I’m saying here, but do you know the difference between resilient channel versus isolation clips? I read that isolation clip method is a little more expensive than resilient channel but doesn’t fail as often as resilient channel, which it sounds like has to be installed perfectly to work and, as you say there are limits to what you can hang on the wall, otherwise it fails. Do you know anything about this?

And again I have the question, let’s say for the whole common wall we only add a layer or 2 of drywall on top of what’s already there. But just for the master bedroom wall, we demo one side of it, replace the fiberglass batts with Rockwool, decouple with isolation clips or resilient channel, and put back up one or two layers of regular drywall (or one layer of QuietRock and green glue?). Will we realize the benefit of significantly lower sound transmission across the master bedroom wall? Or will flanking negate the extra mitigation?

What I’m getting at is, we’ve got long stretches of hallway and stairwells along the common wall where it’s not as important to reduce the sound transmission, and where the expense and disruptiveness of demolition will really pile up, whereas we’ve got a few rooms like bedroom and loft, and half of the main level, where we need more strongly block the sound.


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## stillmand (May 14, 2022)

Genduct said:


> Since you are going to laminate another layer of gyp,  why not blow in some insulation then cover the holes?


Thanks for this. My understanding is that if there are already insulation batts in the wall, you can’t blow in additional insulation.


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## stillmand (May 14, 2022)

Jay Smith said:


> Perhaps a little hard to believe, but the GenieClip RST retrofit assembly is claimed to provide an improvement of 12-18 dB.
> 
> 
> 
> https://pliteq.com/products/sound-control-clip/genieclip-rst/


Thank you. It’s hard for me to tell. For GenieClip and other brands of isolation clips, how much space do you lose compared to screwing a layer of drywall directly into the stud?


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## Jay Smith (May 14, 2022)

stillmand said:


> Thank you. It’s hard for me to tell. For GenieClip and other brands of isolation clips, how much space do you lose compared to screwing a layer of drywall directly into the stud?


Slightly less than 2 inches.

If the builder scaled down to the minimum they were required to do, the separation through the 3rd-floor truss cavity is acoustically doing little or nothing. Same thing in the attic, which is probably separated by only a draftstop. The floor cavity intersection detail shows three layers of gypsum board that were probably omitted. No insulation on the ceiling, gypsum underlayment on the subfloor, or sound isolation mat is indicated. No indication of continuing vertical wall board through horizontal cavities. No indication that I saw to avoid back-to-back penetrations.


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## stillmand (May 14, 2022)

Jay Smith said:


> Slightly less than 2 inches.
> 
> If the builder scaled down to the minimum they were required to do, the separation through the 3rd-floor truss cavity is acoustically doing little or nothing. Same thing in the attic, which is probably separated by only a draftstop. The floor cavity intersection detail shows three layers of gypsum board that were probably omitted. No insulation on the ceiling, gypsum underlayment on the subfloor, or sound isolation mat is indicated. No indication of continuing vertical wall board through horizontal cavities. No indication that I saw to avoid back-to-back penetrations.


Thank you. As you know, we already discovered there is only one layer of drywall on each side of the common wall versus the 2 layers on each side indicated by the blueprint. What would you say are one or two other important components to preventing sound transmission between the two houses that we should check to see if the blueprints were followed, and could they be checked with out making holes in the wall?


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## stillmand (May 14, 2022)

stillmand said:


> Thank you. As you know, we already discovered there is only one layer of drywall on each side of the common wall versus the 2 layers on each side indicated by the blueprint. What would you say are one or two other important components to preventing sound transmission between the two houses that we should check to see if the blueprints were followed, and could they be checked with out making holes in the wall?


Also, let’s say we’re especially concerned about the sound transmission across the master bedroom common wall and the loft common wall. Should we looking at blowing in insulation through the ceiling and floor within a certain distance of those walls? Or will just treating those wall areas themselves help enough?


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## Mark K (May 14, 2022)

stillmand said:


> Thanks so much, happy to give a little more background.
> 
> Thanks for the answer and happy to provide more background. Blueprints called for “2-hour firewall” with 2 layers of 5/8” drywall on each side of the common wall. But in reality they only put in one layer on each side. Builder now claims that they really only had to meet a 1 hour firewall because they say building falls under IRC rather than IBC.
> 
> ...


If the construction documents require something in excess of the code the contractor must provide what is in the construction documents.  In such a situation what is required by the code is irrelevant.


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## Genduct (May 14, 2022)

stillmand said:


> Thanks for this. My understanding is that if there are already insulation batts in the wall, you can’t blow in additional insulation.


If the batts are there then you have your STC value


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## bill1952 (May 14, 2022)

Rock wool is good but cellulose a lot less work in existing wall and pretty good. A combo that exceeded many walls was Fiberock abuse resistant drywall with dense pack cellulose.


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## stillmand (May 14, 2022)

Genduct said:


> If the batts are there then you have your STC value


Not sure what you mean by that? There is 5.5” fiberglass batts in the wall. But the STC is still terribly poor based on the fact we can easily have a conversation with our neighbors through the wall. I’m told the fiberglass batts don’t really help to absorb much sound, and that Rockwool doesn’t much better for that.


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## Jay Smith (May 14, 2022)

stillmand said:


> Thank you. As you know, we already discovered there is only one layer of drywall on each side of the common wall versus the 2 layers on each side indicated by the blueprint. What would you say are one or two other important components to preventing sound transmission between the two houses that we should check to see if the blueprints were followed, and could they be checked with out making holes in the wall?


I would be most interested in the separation of the bedroom floor cavity along the common wall. Maybe the builder would tell you how it was done. Even the three layers shown in the drawings would perform worse than the wall. The architect’s notes clearly present that separation detail with three layers as a fire-resistance measure, so it would seem very likely the builder omitted it or at least two layers of it when they decided to build a 1-hour assembly.



stillmand said:


> Also, let’s say we’re especially concerned about the sound transmission across the master bedroom common wall and the loft common wall. Should we looking at blowing in insulation through the ceiling and floor within a certain distance of those walls? Or will just treating those wall areas themselves help enough?


Aside from code compliance, I would think the acoustical solution is probably to (a) replace existing wall board on your side with resilient channel and two layers of wall board and (b) add insulation and wall board in the floor-ceiling cavity in line with the wall.

That 2nd one would be tedious. You would have to cut into the living room ceiling and work between about 12 trusses in the bedroom floor.


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## stillmand (May 14, 2022)

Jay Smith said:


> I would be most interested in the separation of the bedroom floor cavity along the common wall. Maybe the builder would tell you how it was done. Even the three layers shown in the drawings would perform worse than the wall. The architect’s notes clearly present that separation detail with three layers as a fire-resistance measure, so it would seem very likely the builder omitted it or at least two layers of it when they decided to build a 1-hour assembly.
> 
> 
> Aside from code compliance, I would think the acoustical solution is probably to (a) replace existing wall board on your side with resilient channel and two layers of wall board and (b) add insulation and wall board in the floor-ceiling cavity in line with the wall.
> ...


Thanks Jay, appreciate this. Do you think we could address the master bedroom wall first, see if flanking is still significant enough of an issue, and if so then address the floor-ceiling cavity? 

Also would there be an intermediate solution where we could cut small holes to blow in some insulation into the floor ceiling cavity and skip the addition of wall board there? Would that be less disruptive/expensive?


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## Jay Smith (May 14, 2022)

stillmand said:


> Thanks Jay, appreciate this. Do you think we could address the master bedroom wall first, see if flanking is still significant enough of an issue, and if so then address the floor-ceiling cavity?
> 
> Also would there be an intermediate solution where we could cut small holes to blow in some insulation into the floor ceiling cavity and skip the addition of wall board there? Would that be less disruptive/expensive?


It does seem like addressing the wall first would be worth trying.

The blown insulation idea sounds plausible and helpful, and less disruptive/expensive. I just don’t know how to think about how effective it would be. With this idea of adding mass and resilience to an entire wall there are tested assemblies that can give us a goal like STC 50 and a means to try to achieve it.


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## bill1952 (May 15, 2022)

If adding drywall on resilient channels, I wouldnt remove the existing layer - just add the channels on top of it and add the new layer of drywall


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## tbz (May 15, 2022)

This has become a very interesting topic, I guess since I am still battling the same issue in my place currently.


As noted in my previous posts, not very specific, but as noted by Jay also, the floor cavity became like a bull horn for sound travel, at a minimum I would look at getting in there, the whole way and blowing or installing sound proofing, not just an insulation, for me this reduced a good bit of the sound transfer in the floor system.
Common walls along stair flights, I will assume one of your common walls is along the stair flight and the side of the stringer sits flush with the face of the single sheet of drywall.  Thus adding, like me a single layer of drywall is about the only option you have and that sets the issue for the rest of that exposed wall being uniform.  
Hence adding a channel system or clip system to that existing wall, is not an option because it extends over the stringer and reduces the width of the stair flight.  If your stair flight is wider, over 40", then this might not be a bad option, but I was already only 34" wide between walls.
I first did the green glue method and found the mids were affected, however the lows and some highs there was no difference at all to me, thus when they played music it was the same, except now I could not understand the words until they screamed in a high pitch and well, I got constant heavy base.
Thus, since I was only dealing with 10 sheets of drywall, I pulled everything down, on an internet whim, I put a layer of MLV ($700.00) and then did a 5/8" layer of drywall, taped and spackled and then applied a 2nd layer of 5/8 staggering the seams and then taped and spackled again.
This method for me did reduce the lows a good bit more and did reduce more mids, though both are still present.  Not sure it was worth my time and effort, but I do hear a major difference than just the added 5/8 with green glue from before.  

As to the bedroom without knowing, and this becomes a personal choice, how much floor space you are willing to give up in the name of sound, well one can only speculate.
If you can give up the space, pull down the drywall remove the insulation, and install a system like Rockwools "Safe & Sound" or something better or equal in the existing cavity. Air-gap and then install another metal or wood stud wall, thickness could range from 1.5" - 5.5", depending on what you can give up and then sound proof with the same type of system in the first wall and then 2 layers of 5/8 following best practices with staggered seams and so on.
Being somewhat handy myself, I did all the work myself, thus reducing my costs to materials, and whatever time I had.
But, you need to also make sure they ceiling cavity above and floor cavity below are also done.
I did this on the first floor and I can't hear a thing coming through that wall when the neighbors are in the mist of who is cooking dinner tonight anymore...     Very pleased with this, wish I could have done it along my stair flight.

The bottom line is, 90% of what is really going to work, will not be covered by anything your builder is probably responsible for.

Now here is the big question that those leaning on what the plans said to what is built.

Did you and your neighbor hire a architect/design team to draw the plans and build it for your?
or did the builder, construct the property and sell each of you through a realtor a finished residence, separately?

Because buying a floor plan from a builder and holding them to building it to the exact construction drawings becomes 2 separately different things.
If it's the later, the 2nd does not mean anything because the drawings are not part of the contract.
Only being built to the minimum code requirements does and that is why many states require New Home Warrantees as part of the sale of each new home constructed and sold, to the first owner.


The internet is full of suggestions I found more than a few websites on soundproofing apartments, condos and townhouse very interesting reads.

But this one helped me and I have another I used, just can't find the book mark at this minute, when I do I will post.






						Soundproof Guide
					

The Only Guide You'll Need for all Your Soundproofing Projects




					soundproofguide.com
				




The bottom line is, what's your goal and what's your budget, toss any thought of the original builder getting you to the level of quite you want, just not happening IMO.


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## tbz (May 15, 2022)

As to your question about channel and clips systems, I have no personal experience with them and was told by those that did, that my situation, hanging kitchen cabinets and shelving to stay far away from it.

Thus, they all suggested the wall gapping method, being only 12ft wide with my space (Floor plan on that side 12'-2" x 28'-0" face of inside of balloon - framing built in 1875) I was only 140.5-inches between the inside of the framed walls to begin with.

So, giving up another 4" (1/2" gap & 3.5" stud wall) was huge on the first floor, I went from 140.5" to 136.5" minus another 1.75" of drywall, so face of sheet rock to face of sheet rock on the first floor is now 11'-2.75".  But the layout works with the reduced space and I just ended up a much smaller door to the basement, which is not really useable.   Low Ceilings and well.

Here is the floor concept floor plan I started with you can see the wall shift by the stair flight to the basement.


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## Genduct (May 15, 2022)

bill1952 said:


> Rock wool is good but cellulose a lot less work in existing wall and pretty good. A combo that exceeded many walls was Fiberock abuse resistant drywall with dense pack cellulose.


Personally,  I prefer the INORGANIC fiber glass /  Mineral type product.  I have always been wary of the chemicals used to treat the ground up newspaper (cellulose) product.  The concern comes from the potential of condensation in the wall cavity from air leakage or surface condensation of the sheathing of this porous product.  IMHO


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## Genduct (May 15, 2022)

stillmand said:


> Not sure what you mean by that? There is 5.5” fiberglass batts in the wall. But the STC is still terribly poor based on the fact we can easily have a conversation with our neighbors through the wall. I’m told the fiberglass batts don’t really help to absorb much sound, and that Rockwool doesn’t much better for that.


The sound also travels through the CRACKS AND GAPS as well as through the studs themselves ( hence the staggered stud design where Sound and STC is a real concern).
The density is not as high as mineral, that's true,  but it would be much more if those batts were not there

With Acoustics there is no substitute for MASS for the STC values


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## Genduct (May 15, 2022)

Genduct said:


> Since you are going to laminate another layer of gyp,  why not blow in some insulation then cover the holes?


If this is a real concern,  how about a layer of 1 inch, high density fiber glass insulation with the then the extra layer of drywall"   There are electrical box extensions that can be added to outlets that might help this "FIX"

You'll want to calk those cracks where wall meets the ceiling.   Just think about the "Cross-talk possibility if the wall intersects at the space between joists.
Commercial work often has the walls extend above the suspended ceiling to avoid this similar problem


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## bill1952 (May 15, 2022)

Genduct, on this issue, with sincere all due respect, just have come to different conclusions.

You pour a cup of water into a wall with fibre glass insulation, and you have a cup of water on the sill plate. Do same with cellulose, and it disappears, and can dry later.

Tested, for fire resistance, cellulose performed much better than fiberglass  because it allowed less convection, which to me says it insulates better. That should improve acoustic performance as well.

Cellulose is more opaque than fiberglass, so better at preventing radiant transfer. Just put a flashlight behind each.

Some group studied it for mice and such, and mice don't like it as well as other insulation because the tunnels collapse.

As far as health concerns, Oak Ridge National Labs say no concern. https://timberhomesllc.com/cellulose-fire-safety-and-health-concerns-of-flame-retardants/

But either blow in has to be easier in existing wall compared to removing drywall.


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## bill1952 (May 15, 2022)

Genduct said:


> With Acoustics there is no substitute for MASS for the STC values


Basically agree, though physical separation - distance - is also very effective.  Chorus and band room in a high school for instance, a double cmu wall with say a 8"  air space between them and no physical connection works pretty good, but place a storage room between those two cmu walls, even better. (no doors or other penetrations.)  Move those rooms to opposite ends of corridor,  you can ditch some mass.


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## stillmand (May 15, 2022)

tbz said:


> This has become a very interesting topic, I guess since I am still battling the same issue in my place currently.
> 
> 
> As noted in my previous posts, not very specific, but as noted by Jay also, the floor cavity became like a bull horn for sound travel, at a minimum I would look at getting in there, the whole way and blowing or installing sound proofing, not just an insulation, for me this reduced a good bit of the sound transfer in the floor system.
> ...


Thanks so much for this. Indeed, we did not hire an architect. We put a reservation on the house as it was being built, and then purchased  final product. That said, we believe the blueprints represent a contract, such that the builder should be accountable for 2 missing layers of drywall that are on the blueprints, which were approved by the city, but weren’t actually installed. 

We also believe the builder is obligated to cover the cost of bringing the common wall up from the current STC that an acoustical engineer has estimates as 32, to the STC of 45 required by IRC, which is the applicable code. We realize that an STC 45 still won’t be good enough (although a heck of a lot better than 32). But let’s just say, making up numbers, it would cost $30,000 to get the common wall to an STC 45 and $40,000 to get to an STC 52. If we can compel the builder to cover the $30,000, then the additional $10,000 split between us and our neighbors, who want to solve the problem as much as we do, is potentially doable. Again, making up numbers here, although they may not be far off.


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## Genduct (May 15, 2022)

bill1952 said:


> Genduct, on this issue, with sincere all due respect, just have come to different conclusions.
> 
> You pour a cup of water into a wall with fibre glass insulation, and you have a cup of water on the sill plate. Do same with cellulose, and it disappears, and can dry later.
> 
> ...


Bill,  I like the fact that you too believe: Without the Data, You are Just someone with an OPINION"

But perhaps I am old enough to remember that Cellulose was, and perhaps still is Not Allowed Or discouraged to be used to retrofit old work where knob and tube wiring still exists.
Perhaps not the issue it was a number of years back, but there was and perhaps still is a concern about the chemicals used to "Fire Proof" ground up newspaper" 

I also am old enough to remember the misinformation that the Cellulose people put forward in the late 70's that used efforts like "Victims of Fiber glass" to try to link Fiber glass with Asbestos. This effort lead to Prop 65 in California.  So the Cellulose Industry's track record is somewhat suspect in my mind

Perhaps we can agree to disagree and respect each other's right to follow our preferences


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## bill1952 (May 15, 2022)

I agree, do not blow in cellulose where there id k&t wiring. Seems unlikely in a house new last year.

I recall (the much better funded) fiberglass industry casting aspersions on cellulose as flammable news paper and it was not safe. That led to the cellulose industry producing


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## tbz (May 15, 2022)

stillmand said:


> Thanks so much for this. Indeed, we did not hire an architect. We put a reservation on the house as it was being built, and then purchased  final product. That said, we believe the blueprints represent a contract, such that the builder should be accountable for 2 missing layers of drywall that are on the blueprints, which were approved by the city, but weren’t actually installed.


Without knowing the contract you signed, most builders today building spec or base homes, tend to contract on the floor plans and note someplace that the blueprints and construction documents are not part of the contact, just a code compliant home.  Haven't a clue nor do I want to know, but that is the majority of the business, as this allows them the ability to change things and only be focused on delivering what is based on the floor plan and amenities stated and minimum code compliance.

If your contract is locked into the blueprints that they submitted, then all means, open season.  The STC verified number is stating not 45 but 32, as thus, that is a code compliance issue and is justified requesting that the issue be rectified, my concern would be, will adding the 2 layers of 5/8" take you to a 45? Good chance maybe, but is that the result you are going to be satisfied with?  I am thinking not so much

Only the acoustical engineers have the knowledge and expertise to speculate.     

I guess my point is that if your main concern is the noise level and not the 2 hour fire protection in the IBC, then focus on working with them to get to a result of what you want, better sound proofing.  

Hence maybe you pay to have the walls opened and sound proofing added, and the builder then takes over to install 2 new layers of 5/8 staggered seams with spackling in between, and painting.

Because, if they just add the additional layer they will still need to spackle and paint.  You negotiate for them taking on the cost and redoing the new 1st layer 5/8".

From where I sit, your hanging your hat on double layer drywall and a STC number.  and from my personal experience, I am guessing when the sound tech says yes it meets the 45 STC and there are 2 layers on each side, your still not going to be happy.  But done with the builder...


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## Genduct (May 15, 2022)

bill1952 said:


> I agree, do not blow in cellulose where there id k&t wiring. Seems unlikely in a house new last year.
> 
> I recall (the much better funded) fiberglass industry casting aspersions on cellulose as flammable news paper and it was not safe. That led to the cellulose industry producing


To be fair,  I believe they have info that strongly supports the notion that with the cycles of the cellulose absorbing then shedding moisture, that, over time, the fireproofing chemicals migrate and concentrate in the lower level, thus leaving less fire-resistant cellulose on top of attic / ceiling application.  Or so it has been speculated!

The Victims of Fiberglass was a shameless and self serving attack that they knew was a LIE when they did it


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## Genduct (May 15, 2022)

bill1952 said:


> Basically agree, though physical separation - distance - is also very effective.  Chorus and band room in a high school for instance, a double cmu wall with say a 8"  air space between them and no physical connection works pretty good, but place a storage room between those two cmu walls, even better. (no doors or other penetrations.)  Move those rooms to opposite ends of corridor,  you can ditch some mass.


Bill,  give me a call sometime,  267 784 2401


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## Mark K (May 15, 2022)

If you believe that the contractor violated a contract you should be talking with an attorney.  The attorney will evaluate the legal issues and retain an expert to help support your claim.

This forum will not resolve your problem.  I suspect that much of the discussion here will not be relevant to resolving your problem.


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## stillmand (May 15, 2022)

Mark K said:


> If you believe that the contractor violated a contract you should be talking with an attorney.  The attorney will evaluate the legal issues and retain an expert to help support your claim.
> 
> This forum will not resolve your problem.  I suspect that much of the discussion here will not be relevant to resolving your problem.


Actually this discussion has been extremely helpful. Ultimately I imagine it’s going to be on us to select the soundproofing strategy (of course based on input from an expert) that we are most comfortable will work, and there have been lots of great ideas mentioned here in this discussion.


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## bill1952 (May 16, 2022)

Finally got drawing link to work.  Does that detail really comply with code, even if built that way, which I guess it isn't?  I thought the GWB had to be continous. The continuous plywood floor sheathing seems very questionable, and I wonder if they eliminate a layer of 5/8 on both sides, if they got the three layers between.  But a rotten detail for sound transmission, as has been attested to.


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## redeyedfly (May 16, 2022)

bill1952 said:


> Finally got drawing link to work.  Does that detail really comply with code, even if built that way, which I guess it isn't?  I thought the GWB had to be continous. The continuous plywood floor sheathing seems very questionable, and I wonder if they eliminate a layer of 5/8 on both sides, if they got the three layers between.  But a rotten detail for sound transmission, as has been attested to.
> 
> View attachment 8954


This detail does not comply with code.  They missed 722.6.1.1, max 60 min for calculated wood/gyp assemblies.  Gyp does not necessarily need to be continuous, but a rated assembly does.  You can change assemblies as you go up the wall if they all meet the requirements.  
You don't need a listed assembly for sound but if you build without a listed assembly you must meet a higher standard (50 vs 45 STC) for a field test.


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## bill1952 (May 16, 2022)

Thank you.  I'm no expert on fire barriers/walls/etc. but looked suspicious.  I guess it was approved based on thread.  As far as acoustics, noise isolation generally benefits from the same things that make firewalls work.

I'm sure its possible to frame into a firewall like this but it seems the usually approach is to run joists parallel to the wall.

My condolences to stillmand.


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## Paul Sweet (May 16, 2022)

I wonder if they ever put the gyp board in the floor truss space.  Floors framed with trusses are a great conduit for sounds.


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## bill1952 (May 16, 2022)

Paul Sweet said:


> I wonder if they ever put the gyp board in the floor truss space.  Floors framed with trusses are a great conduit for sounds.


Absolutely. And a lot of acoustical consultants would say that the continous ply had to be gapped.  I don't know if that can be saw cut and maintain the structural integrity of the joists.

It's a lot more than just beefing up the walls.  Need a borescope (do?) and pull some base to look at that detail.


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## Genduct (May 16, 2022)

bill1952 said:


> Finally got drawing link to work.  Does that detail really comply with code, even if built that way, which I guess it isn't?  I thought the GWB had to be continous. The continuous plywood floor sheathing seems very questionable, and I wonder if they eliminate a layer of 5/8 on both sides, if they got the three layers between.  But a rotten detail for sound transmission, as has been attested to.
> 
> View attachment 8954


you said: "The continuous plywood floor sheathing seems very questionable"
It seems to me that that "Diaphram Strength" is what is holding the assembly together.  Especially with the 1 3/4" truss bearing with the triple 5/8 fr drywall


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## bill1952 (May 16, 2022)

Genduct said:


> you said: "The continuous plywood floor sheathing seems very questionable"
> It seems to me that that "Diaphram Strength" is what is holding the assembly together.  Especially with the 1 3/4" truss bearing with the triple 5/8 fr drywall


You may be right, probably are, but it's short circuiting the acoustic separation and, as a non-expert in fire rated partitions, the fire resistance.  So it's necessary to hold together a bad design.  If some jumps on one side, it must be clearly heard and felt on other side.


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## redeyedfly (May 16, 2022)

bill1952 said:


> You may be right, probably are, but it's short circuiting the acoustic separation and, as a non-expert in fire rated partitions, the fire resistance.  So it's necessary to hold together a bad design.  If some jumps on one side, it must be clearly heard and felt on other side.


The subfloor is almost always continuous.  It is a short circuit but there are practicalities like building integrity that cannot be ignored.  There is typically gypsum underlayment to add mass to the floor assembly (stops at the inside face of the unit separation wall) and sometimes sound mat if not carpeted to reduce impact. 

The goal is not perfect sound isolation, it is to mitigate sound transmission to an acceptable level.


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## tbz (May 16, 2022)

redeyedfly said:


> This detail does not comply with code.  They missed 722.6.1.1, max 60 min for calculated wood/gyp assemblies.  Gyp does not necessarily need to be continuous, but a rated assembly does.  You can change assemblies as you go up the wall if they all meet the requirements.
> You don't need a listed assembly for sound but if you build without a listed assembly you must meet a higher standard (50 vs 45 STC) for a field test.


Redeye, 

How does the IBC's 722.6.1 apply to an IRC permit for a 1 & 2 family home?

I don't remember there being an R722.6.1 in my book?


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## redeyedfly (May 16, 2022)

tbz said:


> Redeye,
> 
> How does the IBC's 722.6.1 apply to an IRC permit for a 1 & 2 family home?
> 
> I don't remember there being an R722.6.1 in my book?


The detail quotes IBC 722


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## tbz (May 16, 2022)

My Bad, missed it.... Need thicker Glasses


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## Genduct (May 16, 2022)

bill1952 said:


> You may be right, probably are, but it's short circuiting the acoustic separation and, as a non-expert in fire rated partitions, the fire resistance.  So it's necessary to hold together a bad design.  If some jumps on one side, it must be clearly heard and felt on other side.


structures TRUMPS ( no pun intended) Acoustics I believe
Some mineral batt up there would probably help both areas of concern IMHO


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## bill1952 (May 16, 2022)

I didn't know you could run wood through a firewall.  Fundamental principle of acoustic isolation is structural breaks, because rigid structure transmits sound energy.


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## redeyedfly (May 16, 2022)

bill1952 said:


> I didn't know you could run wood through a firewall.  Fundamental principle of acoustic isolation is structural breaks, because rigid structure transmits sound energy.


Unit separation walls are fire partitions, not fire walls.


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## bill1952 (May 16, 2022)

redeyedfly said:


> Unit separation walls are fire partitions, not fire walls.


Combustible materials can go through fire partitions?


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## redeyedfly (May 16, 2022)

bill1952 said:


> Combustible materials can go through fire partitions?


Yes kinda, it depends.  Fire partitions begin at the top of the sheathing and stop at the underside of the sheathing.  So the sheathing is not part of the fire partition.


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## Genduct (May 16, 2022)

redeyedfly said:


> Yes kinda, it depends.  Fire partitions begin at the top of the sheathing and stop at the underside of the sheathing.  So the sheathing is not part of the fire partition.


Good Answer!


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## ADAguy (May 17, 2022)

Lots of discussion but I have not seen mention of use of lead blankets or lead lined panels to cut off sound? Back in the day we used these for recording rooms and shrinks offices, At Sony we did side by side offices of agents with minimal transmission when listening to loud music.


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## bill1952 (May 17, 2022)

Leaded vinyl was mentioned above. It's mass, but expensive mass compared to other materials. And pretty sure plain lead is not well advised in a house, so leaded vinyl. seems to be $2+ per sf.


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