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Old 01-17-2018, 11:47 AM   #1
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Finnishing attic space (flooring).


Hello everyone. I have about 2000sf of attic space (or an unfinished second story) that I need to start finishing. I am what I would call a capable novice with a lot of questions. Any help is greatly appreciated.

Question 1.
The attic space has 3/4 inch OSB decking loosely secured down with I'm guessing loose fill insulation underneath. When the kids are up there running around it is extremely loud downstairs. What is the best way to silence it? I've done some research and have read that a sound absorbing membrane with another layer of OSB works well and I've been told that it is best to use 2X4s and another layer of OSB to raise it with bat insulation laid between the two subfloors. Any advice?
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Old 01-17-2018, 12:34 PM   #2
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Re: Finnishing attic space (flooring).


First, if you're going to make this conditioned space, I would be inclined to remove the insulation entirely. Something like Roxul Safe n Sound could be used instead but the best sound reduction comes from decoupling the structure.
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Old 01-17-2018, 12:48 PM   #3
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Re: Finnishing attic space (flooring).


Thanks stick\shift. I thought the same thing; however, the contractor I had over believed that for a dual zone hvac system the existing insulation would be beneficial. Forgive my ignorance but by decoupling do you mean raising the floor?
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Old 01-17-2018, 01:06 PM   #4
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Re: Finnishing attic space (flooring).


Hi Sub and welcome to the forum,
If you have talked to a contractor then issues like the depth of the floor joists have been considered, 2x10's or other??
Plumbing, electrical, and heating all need to be planned before the subfloor is secured and permits pulled.

Not sure where you are or when the house was built but a major improvement will most likely need to bring all new work up to current code requirements, like insulation levels and egress.

Do you have vertical walls all the way around or will some of them be sloped following the ceiling? Vaulted ceilings will usually require extra depth and ventilation.

That will get us started.
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Old 01-17-2018, 09:21 PM   #5
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Re: Finnishing attic space (flooring).


Hello Bud and thanks for your help.
1. I live a bit off the beaten path and it is difficult at best to get contractors out here. I did finally get one out here yesterday after looking for about 2 months. He didn't mention the floor joists but did say if I wanted a bathroom he needed to get a structural engineer out to take a look. He was sure that the space as it is could support the additional weight of living space. He also said permits weren't necessary unless i plan on making structural changes.

2. The house is a a modular built in 2008. as fr as i know, everything in the house meets or surpasses code requirements in NC. It has a carpeted stairwell leading to the attic that looks more like an unfinished second story than an attic.

3. The attic floor joists are 2x10s ( not sure of the species) spaced 24". There is 1" tongue in groove OSB sheets covering the entire attic floor with about 7 inches of loose fill insulation beneath.

4. There are 4' knee wall frames with 2x7 rafters, and 2x8 ceiling joists about 12 feet above the floor. There is about 8' of space between the ridge vent and the ceiling joists.

Pictures are attached.

Again, thanks for your time.
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Finnishing attic space (flooring).-image1.jpg   Finnishing attic space (flooring).-image2.jpg   Finnishing attic space (flooring).-image3.jpg  
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Old 01-17-2018, 10:16 PM   #6
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Re: Finnishing attic space (flooring).


It looks like it was build to be finished
The sloped part to the ceiling can be added to for more insulation with air space the horizontal member running thru those rafters would need to be drilled to allow air movement. We don't see air chutes from the soffet area. And there should be solid blocking below the edge of the osb at the nee wall
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Old 01-17-2018, 11:35 PM   #7
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Re: Finnishing attic space (flooring).


I'm always disappointed when a contractor says permits are not needed. One, that isn't his decision to make that is up to the local governing authority. And two, those codes are there to protect you, forcing him to build to predetermined minimum standards and be inspected. Home owners rarely know how to reign in a bully contractor but code officials do. Regardless of structural changes, heating, plumbing, and electrical will most likely need permits.

I think I walked through a model home years ago pretty much the same as yours. The second floor was left just prepared for finishing. But there is still a lot to do up there. You will need to decide on how the roof and side to top attics will be ventilated. How much insulation to use, codes have changed since that was built. You will want blocking under those kneewalls if not there. And more I'm sure as others comment.

IMO you could get off to a good start by inviting your local code official to take a look and help identify what s/he wants to see. They might decline and just go with the pictures but having asked you become a good guy.

Time for some sleep
Later,
Bud
https://energycode.pnl.gov/EnergyCod...rth%20Carolina
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Old 01-18-2018, 04:57 AM   #8
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Re: Finnishing attic space (flooring).


Okay, it's time to admit that the cheaper the laminate flooring is, the cheaper it looks. While laminate flooring has gone a long way, the ugly looking ones should cease to exist, there’s just no room for them inside living rooms anymore.
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Old 01-18-2018, 10:24 AM   #9
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Re: Finnishing attic space (flooring).


1. Ill go look for blocking today when I get home from work. Admittedly I didn't know what you were talking about but a quick google search fixed that. My plan for insulation was to install air chutes against the roof sheathing and insulate to R38 using either bats or bat/foam combo depending on what gets me to R38 within the space constraints of the rafters. With regards to insulation, I have found mountains of conflicting information regarding the facing of the kraft paper. Where I live we heat more months than we cool but only by a month or two. So should the paper face out or in, or should I not use paper and just put up plastic?

2. As far as my original question goes, anyone have advice about whether I should leave the floor insulation in or remove it and what is the best way to muffle the sound of foot traffic upstairs?

3. Nealtw, I had a contractor come out specifically to ask him that question. He said he would cut a square into the center of the member in each bay to allow airflow. I figured a 1-2 inch hole saw would do the trick. My question is if I want to put the hole in the center of the wood to preserve its integrity, how would I manipulate the air chute/insulation so as to not block airflow through the hole?

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Old 01-18-2018, 11:46 AM   #10
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Re: Finnishing attic space (flooring).


Quote:
Originally Posted by SubMiracle View Post
1. Ill go look for blocking today when I get home from work. Admittedly I didn't know what you were talking about but a quick google search fixed that. My plan for insulation was to install air chutes against the roof sheathing and insulate to R38 using either bats or bat/foam combo depending on what gets me to R38 within the space constraints of the rafters. With regards to insulation, I have found mountains of conflicting information regarding the facing of the kraft paper. Where I live we heat more months than we cool but only by a month or two. So should the paper face out or in, or should I not use paper and just put up plastic?

2. As far as my original question goes, anyone have advice about whether I should leave the floor insulation in or remove it and what is the best way to muffle the sound of foot traffic upstairs?

3. Nealtw, I had a contractor come out specifically to ask him that question. He said he would cut a square into the center of the member in each bay to allow airflow. I figured a 1-2 inch hole saw would do the trick. My question is if I want to put the hole in the center of the wood to preserve its integrity, how would I manipulate the air chute/insulation so as to not block airflow through the hole?
That member is never there, But it is part of being a modular I think so best ask some one familiar but for air flow I think 2 or 3 holes 1 1/2"
right next the sheeting.

Paper or poly would go next to the warm side of the structure.
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Old 01-18-2018, 02:00 PM   #11
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Re: Finnishing attic space (flooring).


From an insulation or vapor barrier perspective if the upstairs will be conditioned the same as downstairs then the insulation can stay or go. From a noise perspective fiberglass insulation will do little.

Foot traffic noise will be transmitted directly through the ceiling joists and subfloor. Unfortunately the drywall below is already in place as hanging it from Resilient Channels would have been an option. The most common approach would probably be a good foam or rubber pad under some carpeting.

" My plan for insulation was to install air chutes against the roof sheathing and insulate to R38 using either bats or bat/foam combo depending on what gets me to R38 within the space constraints of the rafters". The air chutes or baffles offer a minimum of space for air flow. Best recommendation is 2" especially when they rum the full length of the roof. But my math does not agree with your r-38, but I don't have the depth of those rafters, 2x8, 2x10, 2x12 ???

Installing the paper facing to the inside is not a problem in all cold climates but not required in all. Where are you?


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Old 01-19-2018, 11:01 AM   #12
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Re: Finnishing attic space (flooring).


1. Bud, I didn't think the fiberglass bats would make much of a difference in terms of sound silencing. However, my question is would the sound isolation gained from installing an additional subfloor raised 2" from the current floor using 2x4s justify the additional labor and cost over just laying another layer of OSB with some sort of membrane in between the two layers?

2. The rafters measure 2x7 (maybe a short 2x8 idk). I would estimate the distance between the floor and the roof ridge is between 20-25 feet. I didn't do any math to get the R-38 number I just read that was a recommended insulation level for a roof. I'm in NE North Carolina so we run ac more often than heat and it gets pretty humid here.
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Old 01-19-2018, 12:31 PM   #13
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Re: Finnishing attic space (flooring).


Sound reduction is part science and part experimentation so your guess is probably as good as mine. Search for sites with that specific knowledge.

With a 7" depth if you allow the minimum of 1" for an air gap that leaves you with 6" for insulation. I allow r-3.5 per inch for fiberglass insulation giving you r-21. 6" Roxul (5.5") is R-21 and would give you 1.5" for an air gap (better) and a big plus being as dense as it is. In reality the performance of fiberglass insulation exposed to air flow on top should be derated. Because Roxul is so dense it is far less subject to that derating. Yes it costs a little more but it would give you a better job.

But, neither option meets the r-30 or r-38 whichever is required.

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