Second Floor Noise Insulation

[EasyE]

I currently have a metal build style house where I built the bottom floor and decked the second floor for a future built out. I am living downstairs and it is finished out. The ceiling/floor joist construction is 16" wooden trusses on 16" centers with 1 1/8 advantech decking on top glued and ring shank nailed. The ceiling has fiberglass bat insulation in it.

I have started framing the second floor and noticed the insulation doesn't help the sound level at all, you can hear a cat walk across the floor from down below. I'm sure most of this is translated directly though the ceiling trusses to the sheetrock below since there is no insulation break there. The final plan calls for an engineered style hardwood floor on the second deck and some tile in the bathrooms. I am wondering if I can put down some 1/2 - 3/4" foam board over the subfloor then some 1/4" hardiboard/concrete board over that and screw it down. Then I would glue down my wood floors. Am I asking for problems with this method?

I have seen the thin roll out insulation that is supposed to be put under the flooring on second floors but I don't think this is sufficient and then I am having to nail down the wood flooring through that instead of gluing....?

Thoughts?

 

[egdede]

If you can repurpose that fiberglass elsewhere, rock-wool will give much better results. I believe the foam board would be fine but make the hardwood feel like a lesser laminate. If you can rock the ceiling of the first floor the roll-foam can be used their to some effect.

 

[ez-duzit]

...I am wondering if I can put down some 1/2 - 3/4" foam board over the subfloor then some 1/4" hardiboard/concrete board over that and screw it down. Then I would glue down my wood floors...

Thoughts?

Why put money into a science project? Unless you simply want to experiment, get help from a professional.

 

[billconner]

I think you want to block noise transmission from lower level to upper level? What is existing ceiling.

First, flanking paths need to be sealed tight. A concrete floor won't help much if there are holes, like around flus, pipes, and of course stairs. Sound will fine weakest path, just like a hole in a boat.

After that, you need some acoustic fuzz in all joist spaces. Fiberglass, rockwool, cellulose, wool, cotton, doesn't matter much. At least 3".

Then add a drywall ceiling to bottom but mount on resilient channels. Like hat channel but with holes. Use at least 5/8 drywall, multi layer if possible, and match weight to channels. Seal gaps and edges with a resilient caulk.

The underlayment might reduce 2nd floor foot fall noise downstairs but won't block sound transmission noticeably.

 

[billconner]

Was looking for resilient channels and came across this: http://www.jglacoustics.com/acoustics-rc_1.html Good background. I have worked with Stan Roller since 1980s on many performing arts buildings. Stan was corporate acoustician for USG at one time and authored most of their literature on sound transmission as well as supervised the testing at Riverbank Laboratories.

 

[EasyE]

The bottom floor is finished and the sheet rock is screwed directly to the floor joists/trusses above. The subfloor is already on the second level so there is no way of going back inside the ceiling without ripping it out, so in short Im not opening it up. Im looking for a way to dampen sound on top of the exisiting subfloor then lay my finish floor over..

Maybe I wasn't explaining this very well. If you are downstairs, you can hear someone walking around upstairs very easily. I want to dampen this noise.

 

[FMB4]

Install extra thick carpet pad and carpet on the 2nd floor.

 

[EasyE]

Going to be hardwood flooring upstairs.

 

[Samh]

There is a video on youtube about best soundproofing options. If I remember correctly, two layers of sheetrock was the best band for the buck

 

[PoorUB]

A layer of gypcrete over the floor will help a lot.

 

[EasyE]

There is a video on youtube about best soundproofing options. If I remember correctly, two layers of sheetrock was the best band for the buck

Too late for that. Im living on the first floor.

A layer of gypcrete over the floor will help a lot.

Never heard of this one, had to look it up. Wonder what this would cost?

 

[billconner]

If your trying to prevent second floor foot fall from being heard down stairs, yes, as layer of something soft between subfloor and finish floor (hardwood?) will help. Last I looked (last year) cork was least expensive. I found grace ice and water shield was also marketed do or this with a different name and a multiple of the price.

Get some cork or spare pieces of ice and water or both, just lay it on sub floor and lay a piece of ply on top, and test. Listen downstairs while someone is on sample.

Flanking paths still important. If you are covering subfloor, consider blowing cellulose or fibreglass in joist cavities. Just one 3 or 4" hole and a loaner machine from a big box store.

Another layer if drywall would help a lot if the existing is 1/2". 5/8" not so much. For acoustics, there is no better spent small amount of money than always using 5/8".

Sound isolation was a fundamental in my work the last 40 years. Expensive products promising fantastic results are probably snake oil.

 

[billconner]

Regarding the hypocrite, it would help. Similarity as so would any layer of heavy stuff. 3/4" particle board, durock, even gypsum if it could be protected. I'd put it over the resilient layer - cork, etc.

 

[EasyE]

Thanks that is helpful. I like the gypcrete stuff but would rather try and save cost and perform the work myself. Obviously I couldnt do gypcrete, but using an underlayment layer and putting some durock over it would be easy. Would I be ok just screwing the durock down (sandwiching the sound deadening underlayment) then gluing my wood floor directly to that?

 

[billconner]

I'm not good enough to know how much the fastener will transmit sound. Some but I just don't know if it will be noticable.

I'd feel better about particle board or ply and just let I float, held together by the wood flooring. But even nailed/screwed I think you'll notice a big difference. You could glue it down but I don't think durock will hold the flooring nails.

I encourage the test before doing it all. It should give you a good idea if it's worth it. I think you'll be pleased.