# Replace 2x4 with 2x6 walls



## jackpine (Sep 3, 2008)

I am tearing out a 30 foot long wall in my house, putting in a double sliding door and two windows. The original wall has two large windows and a door, built with 2x4 studs. Everything is going to go, siding, interior paneling and all the doors and glass. My plan was to rip some strips of 2xs and add them to the 2x4 studs to bring them to 2x6 dimensions. Others tell me to just tear the wall down and re-frame with 2x6 from the get go. What do the experts here suggest? I have windows, patio door (and extension jams) purchased and waiting for warmer weather. Anderson 400 series.


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## Gary in WA (Mar 11, 2009)

Keep in mind with a complete tear-out, the rafters/ceiling joists need the proper nailing (which may require roof section removal, if unable using palm nailer) to the top plate.(If one-story). Along with positive ties with metal H-1's, if required. You would need to add anchor bolts in the concrete (if so) to bring the wall up to today's Code. Pull the wiring involved and install again. 
Will you be insulating outside of siding to meet/exceed today's minimum Code, or just adding cavity insulation? You could do both to make up for the large window heat loss. Or just furr the existing, adding 1/2" foam on the inside, at the drywall for a thermal break. Either way, be sure to use the ADA with drywall; http://www.buildingscience.com/docu...rs/air-barriers2014airtight-drywall-approach/ Foam board outside is the best approach to keep your sheathing (especially OSB) from reaching the dew point on the inside; http://www.greenbuildingadvisor.com...lating-minimum-thickness-rigid-foam-sheathing

http://www.greenbuildingadvisor.com/blogs/dept/musings/are-dew-point-calculations-really-necessary

If on the sunny side of the house, use a rain-screen approach; http://www.greenbuildingadvisor.com/blogs/dept/musings/when-sunshine-drives-moisture-walls

What will you be using for a vapor retarder/barrier?

Gary


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## jackpine (Sep 3, 2008)

I am leaning towards tearing the old out and replacing with new studs and top, bottom plates. So, new insulation, vapor barrier, sheathing, (osb) siding, and on the inside, poly and sheetrock. It just seems to be the easiest way. I will have to build a temporary wall for support as I tear it out. I am spending a ton on sliding patio doors and windows, why skimp on the construction. Still open for knowledge and advise as I do this.


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## Avadon (Apr 20, 2011)

jackpine said:


> I am leaning towards tearing the old out and replacing with new studs and top, bottom plates. So, new insulation, vapor barrier, sheathing, (osb) siding, and on the inside, poly and sheetrock. It just seems to be the easiest way. I will have to build a temporary wall for support as I tear it out. I am spending a ton on sliding patio doors and windows, why skimp on the construction. Still open for knowledge and advise as I do this.


I'm thinking it's six one way and 1/2 dozen the other. Is there any reason I wonder why the 6" would be stronger than the 2x4 with strip screwed into it? I'm guessing probably not. It sure will be amazingly easier to add to the wall than to take all that out if there is a lot of electrical, plumbing, etc. etc. But to rip it out is probably the A+ way to do it. I guess to me it would depend on whether or not your staying in that house for a long time or if your just sprucing up to sell down the road. 

I've never heard of anyone saying that adding strips to existing lumber is not to code, but if anyone knows i'd like to hear it. I guess you are adding the weight of a 2x6 wall to what is a 2x4 constructed wall which may mean extra support.


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## Wildie (Jul 23, 2008)

I'm no expert, but there's no way in hell that I would be removing a whole wall. Especially an outside wall. Invariably, outsie walls are carrying a structural load.
If you wish to make the wall thicker to add insulation it can be furred out using 2X2's.
However, if you want more insulation an easier way would be to add sheets of expanded foam insulation on the outside of the 2X4 framing and use batt insulation between the studs.
2X6 studs are used as an economical way of making walls thicker, so that more insulation can be added, in new construction. Just to rip out a whole wall to add 2X6 studs makes no economic sense. :no:


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## jackpine (Sep 3, 2008)

Wildie said:


> I'm no expert, but there's no way in hell that I would be removing a whole wall. Especially an outside wall. Invariably, outsie walls are carrying a structural load.
> If you wish to make the wall thicker to add insulation it can be furred out using 2X2's.
> However, if you want more insulation an easier way would be to add sheets of expanded foam insulation on the outside of the 2X4 framing and use batt insulation between the studs.
> 2X6 studs are used as an economical way of making walls thicker, so that more insulation can be added, in new construction. Just to rip out a whole wall to add 2X6 studs makes no economic sense. :no:


I can see your point, but my thoughts are if I am replacing windows and doors along the entire wall, and the new windows and doors are not even close to being the same size or in the same locations, I am basically having to rebuild the wall anyway. So why not beef it up, better insulate it and make it new. The cost of the new insulation and studs is minimal compared to the 5 grand in windows I am sticking in. This wall overlooks a lake.


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## Avadon (Apr 20, 2011)

jackpine said:


> I can see your point, but my thoughts are if I am replacing windows and doors along the entire wall, and the new windows and doors are not even close to being the same size or in the same locations, I am basically having to rebuild the wall anyway. So why not beef it up, better insulate it and make it new. The cost of the new insulation and studs is minimal compared to the 5 grand in windows I am sticking in. This wall overlooks a lake.



I've thought about your dilemma over the last few days as surely there is time to add furring strips and surely there is a time when you simply must replace the whole wall. As you said, if it wasn't for all the windows and doors your installing in that wall I would say your best option is just adding the strips. But your putting in so much into that wall that I think you would be crazy modding a 2x4 wall to accept all that expense. After all, taking down the 2x4 is mostly just labor and time and not a huge expense. If you don't do it right and build it with 2x6 I have a bad feeling you'll regret it everytime you look out those windows and put your hand against the wall. 

I'm in the same boat except on one wall I have no choice but to add furing strips to bring 2x3's to 2x4's or tear out a whole wall where I just finished all the drywall and texture on that side beautifully. And it's painted and all the trim is done. So furring strips are the order of the day. The other three walls in that closet i'll take down piece by piece and reframe with 2x4. So I do think there is a time and place for each tactic. 

well that's my 2cents. :thumbsup:

ps.. not to mention that there is many a slip between a cup and a lip when doing those furring strips. You literally have to rip each one on a case by case basis and check to make sure each strip is going on level and plumb. If your not careful the drywall could look really wierd if those strips aren't excellently installed. And if anyone does those furring strips I'd suggest ample PL Premium and a high grade screw (thousands of them)


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## tcleve4911 (Nov 6, 2010)

Ripping out the whole wall sounds easy when you're just addressing the new openings. It's when it comes down to tying into all the small details that you will realize how much harder and longer building a new wall will take.
Not worth it IMHO.

Do all your framing for your new doors and windows with 2x6.
Then fur the rest of the wall to the new "plane".

....signed,
Remodeler for 30 years. Done it both ways.


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## jackpine (Sep 3, 2008)

tcleve4911 said:


> Ripping out the whole wall sounds easy when you're just addressing the new openings. It's when it comes down to tying into all the small details that you will realize how much harder and longer building a new wall will take.
> Not worth it IMHO.
> 
> Do all your framing for your new doors and windows with 2x6.
> ...


Could you expand on the small details that I am probably not thinking of?


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## tcleve4911 (Nov 6, 2010)

Existing corners need to be separated from the return corner and now you have to come up with an inside nailer for your wallcovering.
Top plate needs to be tied into rafters. (think about how to get at the last one on each end)
Shoe will extend into your existing flooring dealing with details in the corners.

Maybe you don't mind overcoming those types of extra work.


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## jackpine (Sep 3, 2008)

tcleve4911 said:


> Existing corners need to be separated from the return corner and now you have to come up with an inside nailer for your wallcovering.
> Top plate needs to be tied into rafters. (think about how to get at the last one on each end)
> Shoe will extend into your existing flooring dealing with details in the corners.
> 
> Maybe you don't mind overcoming those types of extra work.


Thank you. These are things that I did think about. The other walls will be re-done as this one is in the future, but not right now due to time and money. This floor is the middle floor, so the rafters are not the issue. I am open to any suggestions though, especially from a seasoned re modeler!


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## tcleve4911 (Nov 6, 2010)

I guess my reply would be....
Since the building has been standing on it's own for a while, the only reason for the added wall depth is for insulation.

So do it with whatever way you are comfortable.
If building a temp wall for support and dust protection is the way you like...then go for it.

If my way makes sense, then do it that way.

There's always more that one way to do any project and they can all be the right way.:thumbsup:


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## tcleve4911 (Nov 6, 2010)

Wildie said:


> If you wish to make the wall thicker to add insulation it can be furred out using 2X2's.


:no: 2x2 = 1-1/2" x 1-1/2" . 

The difference between 2x4 and 2x6 = 2" 
(3-1/2" and 5-1/2")


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## jackpine (Sep 3, 2008)

I guess in my minds eye, I see it easier. The ceiling is going to be re-rocked eventually too. Maybe I am not explaining the project very well. Once I start tearing the paneling off I may decide to do it differently. No plumbing and only a light switch and two outlets on the wall. It is insulated like [email protected] right now, and the wood paneling is warped. I can look right in to the wall in a couple joints, and I see foil faced insulation.


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## Wildie (Jul 23, 2008)

tcleve4911 said:


> :no: 2x2 = 1-1/2" x 1-1/2" .
> 
> The difference between 2x4 and 2x6 = 2"
> (3-1/2" and 5-1/2")


 That 1/2" would give almost R2 in fibreglass insulation. Hardly worth the trouble of ripping the furring to be exactly 2". I doubt that the payback would be worth the time and labor to do so.

The OP is intending to increase the window openings, so as to enjoy the view. This alone will increase the heat loss to the extent that whats left of the wall is superfluous.


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## tcleve4911 (Nov 6, 2010)

Wildie said:


> Hardly worth the trouble of ripping the furring to be exactly 2". I doubt that the payback would be worth the time and labor to do so.


It'll be worth the trouble when your studs are 1/2" out of plane with each other.....:whistling2:

....are you suggesting to just ignore the wave the wall would have in it?
:huh:


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## Wildie (Jul 23, 2008)

tcleve4911 said:


> It'll be worth the trouble when your studs are 1/2" out of plane with each other.....:whistling2:
> 
> ....are you suggesting to just ignore the wave the wall would have in it?
> :huh:


 :huh: I must be having a seniors moment, as I'm not following you about the wave. Was a wave mentioned in a previous post and I missed it?


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## jackpine (Sep 3, 2008)

I will get a picture of the offending wall, that may help everyone see it.


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## tcleve4911 (Nov 6, 2010)

Wildie said:


> :huh: I must be having a seniors moment, as I'm not following you about the wave. Was a wave mentioned in a previous post and I missed it?


No it was not mentioned earlier.
I used it as a description for the studs being out of plane with each other.

A 5" stud installed next to a 5-1/2" stud will create a "wave" or an uneven plane.

sorry.......


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## jackpine (Sep 3, 2008)

Here are some photos. First, the view from the deck, then some shots of outside and inside. Lighting didn't allow inside shots to turn out so good. These windows and the door are junk. Snow fills in between the storm and the glass during blizzards. We lose a bunch of heat from this wall right now.

As you can see, still cold here in northern MN. Ice not out of the lake yet. I wouldn't walk on it though!


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## jackpine (Sep 3, 2008)

The ceiling joist run perpendicular to the wall, the floor joist run parallel.


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## tcleve4911 (Nov 6, 2010)

Thanks for the pics.
Gun for the door to door salesmen???:laughing:

Is that T-111 siding?

Is that a deck above?

Are you leaving the siding or replacing with new?

T-111 is a bear to flash properly.
Typically the windows and doors are attached directly to the framing, counter-flashed and T-111 installed around the opening.

Soooo if you're ripping off all the siding......oh shoot...I'm still not convinced either way.

I would decide what my finishes will be and work backward from there.
I think the wall thickness and whether you remove all the wall or not, is the least of your initial decisions.

Just my 2¢ 
Nice place:thumbsup:


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## jackpine (Sep 3, 2008)

Yes siding is being replaced with cedar bevel 6 inch. Windows and doors trimmed with rough sawn 2x4 cedar. Yes deck is above as well. All is getting replaced, decks too. BB gun is just for kicks!


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## tcleve4911 (Nov 6, 2010)

So is it T-111 existing?

That's your sheathing and siding...........


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## jackpine (Sep 3, 2008)

T 111 is coming off, replaced with osb, then the cedar bevel siding. Entire house eventually, but right now one wall at a time. I may use the T111 as sheathing and side over it elsewhere, but for this wall since so much is changing I am going with OSB


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## tcleve4911 (Nov 6, 2010)

2 stories?


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## jackpine (Sep 3, 2008)

Yes....


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## jackpine (Sep 3, 2008)

Rough opening for the slider is 9'9 3/4". Wonder if I need to buy a laminated beam for the header or just double up a 2x.


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## tcleve4911 (Nov 6, 2010)

10' span with 2nd floor joists bearing on it .......overbuild if anything.

Did you mention what brand of 9' slider?
I just replaced 2 of them with Marvins.


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## jackpine (Sep 3, 2008)

400 Series Anderson. Frenchwood glider. Nice, I like your work. Busy next week?


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## tcleve4911 (Nov 6, 2010)

Good choice......sorry...I'm busy....:laughing:

But I'll be watching for your progress posts...Good Luck:thumbsup:


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## jackpine (Sep 3, 2008)

I most def. will be coming on here and getting advise as I go. I need some warm days though, before I start. Next weekend looks possible.


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## Wildie (Jul 23, 2008)

tcleve4911 said:


> No it was not mentioned earlier.
> I used it as a description for the studs being out of plane with each other.
> 
> A 5" stud installed next to a 5-1/2" stud will create a "wave" or an uneven plane.
> ...


 Thanks for the clarification, now I understand where you were coming from. What you say is true and would have to be taken into consideration.

The OP says he will post a photo and that may change my thoughts.

My concern was that modifying a load baring wall is quite an undertaking. If the wall is to be 90% glass and money is no object, a beam would have to placed and this would be a major factor in whether to modify or replace the wall.


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## Wildie (Jul 23, 2008)

I missed the photos before I made my last post. 

It looks to me that the wall in question supports the roof, the second floor wall and upper deck?
Is there a beam in there already? Or are there lintels over the door and windows?
If the plan is to install patio doors, a beam will surely be required. I have sliding patio doors at my place and I would not consider these again. In fact, I'm considering having them taken out and replaced with French doors. Sliders don't seal up very well.
I think that you will have to decide what type of openings that you want and the type of siding. Then work back from there.
And if a beam is required, the upper deck will have to be removed temporarily, and its ledger reattached to the beam.
I would suggest that you would employ a structural engineer for advice. Its too complex for an amateur like myself. 
For me, I would fur it up inside, insulate it and install good doors and windows. It may cost upwards of $5000 to build out the existing wall. If the wall is replaced and a beam installed, it may be $50,000. I say this, as I have just completed cosmetic renos. in my present home and its just tallied up to $25,000 and I have made no structural changes.


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## Gary in WA (Mar 11, 2009)

Appears you are in Zone 7, R-21 required (minimum) in the walls; http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_11_sec001_par001.htm

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_11_sec002.htm

I suggest foam board outside to keep your OSB dry from interior R.H; http://www.greenbuildingadvisor.com/blogs/dept/musings/how-risky-cold-osb-wall-sheathing

http://www.greenbuildingadvisor.com...lating-minimum-thickness-rigid-foam-sheathing

Calculator your dew point; http://www.greenbuildingadvisor.com/blogs/dept/musings/are-dew-point-calculations-really-necessary

I’d go with a rainscreen if allowed in your area. OSB, Tyvek, foam with seams taped, gap by strapping, back-primed Cedar siding. http://www.greenhomebuilding.com/pdf/RainScreen.pdf

Need better support than one floor joist below, running parallel to wall if total replace, for temp wall.

Gary


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## jackpine (Sep 3, 2008)

I talked to a structural engineer this morning. He explained it to me much more thorough than I had even thought. Basically he said that I can do what I want to do, but I need to make sure that I carry the gable end of the roof load all the way down to my foundation. He said best scenario would be a laminated beam the entire length of the the wall with double crippler studs each side of the patio door, then make sure I have studs below them on the basement wall foundation. Since I am going to be working this myself, he said I could also just use a laminated beam above the patio door, roughly 10' 2" or what ever it works out to be with the RO for the door. Then, again I need to make sure that I see the weight carried to the foundation. Any structural work I do above this floor also needs to be done in a manor that carries the load properly. He liked the idea of me replacing the entire wall instead of piece mailing it together. I feel better, and confident now.


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## screwy (Mar 12, 2011)

Have you considered building a 2nd 2x4 wall? This is what i did in a similar situation in my house. I build a second wall 1/2" away from the exterior wall. This made the exterior wall solid insulation, 1/2 air gap, 2nd 2x4 wall with wiring and such, then vapour barrier. This makes for some very nice window sills and jambs, plus you will never notice the room is any smaller. 

Just a thought.


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## Wildie (Jul 23, 2008)

jackpine said:


> I talked to a structural engineer this morning. He explained it to me much more thorough than I had even thought. Basically he said that I can do what I want to do, but I need to make sure that I carry the gable end of the roof load all the way down to my foundation. He said best scenario would be a laminated beam the entire length of the the wall with double crippler studs each side of the patio door, then make sure I have studs below them on the basement wall foundation. Since I am going to be working this myself, he said I could also just use a laminated beam above the patio door, roughly 10' 2" or what ever it works out to be with the RO for the door. Then, again I need to make sure that I see the weight carried to the foundation. Any structural work I do above this floor also needs to be done in a manor that carries the load properly. He liked the idea of me replacing the entire wall instead of piece mailing it together. I feel better, and confident now.


 Now you will have to see how much money you will need to do this?
Screwy, mentioned build another wall inside of the first one and this could have merrit also.
I did this once, also and taking 5" from the room is hardly noticed.

P.S. What did he say about the 2nd level deck?


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## chrisBC (Dec 28, 2010)

Have you thought about using spray foam insulation?

will give you a better r value, possibly save you from building out your 2x4 wall like you are talking about to achieve better insulation, won't need a vapour barrier either.


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## tcleve4911 (Nov 6, 2010)

jackpine said:


> He liked the idea of me replacing the entire wall instead of piece mailing it together. I feel better, and confident now.


Good for you.
Sounds like you're on the right track.

Budget is always an issue but do it once and do it right.:thumbsup:


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## jackpine (Sep 3, 2008)

chrisBC said:


> Have you thought about using spray foam insulation?
> 
> will give you a better r value, possibly save you from building out your 2x4 wall like you are talking about to achieve better insulation, won't need a vapour barrier either.


I have, and I may go that route even though I use a 2x6 wall, and even though I have already purchased the insulation.


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## tcleve4911 (Nov 6, 2010)

Foam also adds structural integrity .....


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## jackpine (Sep 3, 2008)

Wildie said:


> Now you will have to see how much money you will need to do this?
> Screwy, mentioned build another wall inside of the first one and this could have merrit also.
> I did this once, also and taking 5" from the room is hardly noticed.
> 
> P.S. What did he say about the 2nd level deck?


Everything is purchase right now for the project except the laminated beam. Cost will be mostly in glass, I figured roughly 6500 for everything, not including the replacement of the old deck which I may not do right away.

The 2nd floor deck is not really an issue. It is small and attached to the rim joist not the studs.


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## jackpine (Sep 3, 2008)

tcleve4911 said:


> Foam also adds structural integrity .....


The engineer recommended foam, but he didn't mention integrity he mentioned that it seals everything up much better. I may buy one of those kits and do it myself.


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## jackpine (Sep 3, 2008)

One step that was encouraged was to try to keep the top plates intact for several feet out from the corners. Stagger the cuts and splice in to match the new 2x6 top plates. This will tie in the corners much better.


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## Gary in WA (Mar 11, 2009)

SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation. BIBS is effective though you will need a poly or other v.b. inside for best results. SPF directly on OSB without either a rainscreen or v.b. is asking for problems. http://www.nrc-cnrc.gc.ca/eng/ibp/irc/ctus/ctus-n32.html

http://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh/?searchterm=foam%20board%20in%20walls

Click on “G”- Conclusions; http://www.buildingphysics.umn.edu/CTteardown01/default.htm#A 



Gary


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## jackpine (Sep 3, 2008)

GBR in WA said:


> SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation. BIBS is effective though you will need a poly or other v.b. inside for best results. SPF directly on OSB without either a rainscreen or v.b. is asking for problems. http://www.nrc-cnrc.gc.ca/eng/ibp/irc/ctus/ctus-n32.html
> 
> http://www.buildingscience.com/docu...nd-the-gap-eh/?searchterm=foam board in walls
> 
> ...


Not sure what SPF is.


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## MLMIB (Aug 12, 2010)

jackpine said:


> Not sure what SPF is.


I think SPF is spray foam, don't know what BIBS is...


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## chrisBC (Dec 28, 2010)

GBR in WA said:


> SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation. BIBS is effective though you will need a poly or other v.b. inside for best results. SPF directly on OSB without either a rainscreen or v.b. is asking for problems. http://www.nrc-cnrc.gc.ca/eng/ibp/irc/ctus/ctus-n32.html
> 
> http://www.buildingscience.com/docu...nd-the-gap-eh/?searchterm=foam board in walls
> 
> ...


 
That's interesting, i've never heard of the 8''s before. I'm sure i've seen it sprayed on the job with 2x4 and 2x6 walls, no vb needed. 

Could vary from area to area, i'm not a big fan of the vapour barrier anyways.


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## jackpine (Sep 3, 2008)

Time has come, work load small enough now and the weather is going to cooperate. Started tearing stuff down yesterday and the big wall will be installed this weekend. I will get some photos up for you all to watch me.


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## jackpine (Sep 3, 2008)

Project is nearly complete. One question. Can i screw windows to the jam through the shims or just rely on the nailed flanges to hold it in place?


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> SPF is not a vapor barrier unless 8" thick. At 2", it is close to same perms as paper faced on insulation.


*This is a false statement.* There are a variety of spray foam mixes with a varying level of permeability. The closed-cell Icynene MD-C-200 (2 lbs mix) is considered a vapor barrier at only 2". If you go with the open-cell formula then the thickness required to become a vapor barrier increases.


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## Gary in WA (Mar 11, 2009)

You may be confusing vapor retarders with vapor barriers. Icynene C-200 is a retarder until +12" thick, then it's a vapor barrier. 
http://www.icynene.com/assets/documents/pdfs/Products/MD-C-200/ICYNENE-MD-C-200-Product-Specs-US.pdf

You can spray a coating on SPF if you need the vapor barrier capabilities: in a cold climate: http://www.icynene.com/vapor-barriers/

I’m talking about a true vapor barrier, not retarder. From Building Science: “A vapor retarder is defined as follows:
Vapor Retarder*: The element that is designed and installed in an assembly to retard the movement of water by vapor diffusion.
The unit of measurement typically used in characterizing the water vapor permeance of materials is the “perm.” Several classes of vapor retarders are further defined as follows [4]:
· Class I Vapor Retarder: 0.1 perm or less
· Class II Vapor Retarder: 1.0 perm or less and greater than 0.1 perm
· Class III Vapor Retarder: 10 perm or less and greater than 1.0 perm
· Test Procedure for vapor retarders: ASTM E-96 Test Method A (the desiccant method or dry cup method)
Finally, a vapor barrier is defined as:


Vapor Barrier: A Class I vapor retarder.” 
 http://www.buildingscience.com/docu...rol-for-new-residential-buildings?full_view=1 
Which the latest IRC copies: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_6_sec001_par005.htm
Vapor retarder, not barrier: http://www.sprayfoam.com/mnps/fullthread.cfm?threadid=11908&mnforumid=2&mnboardid=5&startat=1

All in the terminology: http://www.greenbuildingadvisor.com/blogs/dept/musings/vapor-retarders-and-vapor-barriers

Good read: http://www.buildingscience.com/documents/reports/rr-0410-vapor-barriers-and-wall-design




Gary


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> You may be confusing vapor retarders with vapor barriers. Icynene C-200 is a retarder until +12" thick, then it's a vapor barrier.


There is certainly an eternal debate about what is and isn't a "vapor barrier". To a scientist a vapor barrier is an impermeable substrate (aka 0.0 perms). To a building official a vapor barrier is a substrate with <1.0 perm. While the latter is technically a vapor retarder, for the functional reality of building <1.0 perm is essentially a vapor barrier.

The different classes for vapor retarders you listed is correct. The 2009 IBC section 1405.3 requires a class I or class II, which is <1 perm. Icynene MD-C-200 is 0.9 perms at 1.5". Most contractors spray in 1" increments, so 2" of Icynene MD-C-200 is considered a "vapor barrier" by the building officials.


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## jackpine (Sep 3, 2008)

AGWhitehouse said:


> The IBC calls a vapor barrier as anything with 1 perm or less. Read the Icynene cut...it is 0.9 perms at 1.5". Most contractors spray in 1" increments, so 2" of Icynene MD-C-200 is considered a vapor barrier by the building code. Scientists may argue otherwise when analyzing against the galaxy, but code officials could care less.


I am not spraying insulation, putting in fiberglass batting. Cedar siding, 30lb felt, 1/2 inch OSB, poly, sheetrock. Thats the plan. I can't afford spray foam.


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## AGWhitehouse (Jul 1, 2011)

jackpine said:


> I am not spraying insulation, putting in fiberglass batting. Cedar siding, 30lb felt, 1/2 inch OSB, poly, sheetrock. Thats the plan. I can't afford spray foam.


Good plan, I personally don't like spray foam...just clarying information about it.


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## Gary in WA (Mar 11, 2009)

For those interested in vapor barriers/retarders, Icy is a Class 2, semi-impermeable foam with a perm rating of 1.35 per inch thickness (a little less than rigid foam board). 
When doubling the thickness, 1/2 the perm rating; 

1.35 =1" 0.68= 2" (less than faced f.g.insulation) 0.34= 4" (close to plywood) 0.17= 6" (still semi-impermeable Class 2)

and 0.084= 12" a vapor barrier. If you live in Alaska or Canada and if they require a Class 1 (impermeable) v.b., you need to cover the foam with a v.b. coating or spray 12" thick...... http://www.icynene.com/vapor-barriers/

Research to understand better; http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

http://www.dyplastproducts.com/water_vapor_permeance.htm

http://www.buildingscience.com/documents/reports/rr-0412-insulations-sheathings-and-vapor-retarders

http://www.buildingscience.com/documents/digests/bsd-014-air-flow-control-in-buildings


jackpine, have you sided already? One problem is cedar wicks water, use two layers of paper for better protection. I would use foam board outside to raise the dew point temperature of the OSB, and not use poly inside, rather faced insulation or a “smart vapor retarder”, pp #18-20 for North of you at International Falls; http://www.buildingscience.com/documents/reports/rr-0410-vapor-barriers-and-wall-design

http://www.forestprod.org/woodprotection06tsongas.pdf

http://www.allcityimprovements.com/roofing/airspace.html
Granted, stucco here, though good for possible exterior leaks; http://www.energy.wsu.edu/ftp-ep/pubs/building/project/importance.pdf

How will you be flashing the windows- top and bottom?

Have you seen “rain screen”?

Gary


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## jackpine (Sep 3, 2008)

I have not yet sided, it is prepped with one layer of 30lb felt. Normal window flashing tape. I put it on over the felt already, but it is peeling off so will have to re do it before I side. Plan on siding in early August. 

I would consider two layers of felt and the faced insulation and no poly if I knew why, but no rain screen. I looked into it and nobody is doing it, most never heard of it.


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## AGWhitehouse (Jul 1, 2011)

GBR in WA said:


> Icy is a Class 2, semi-impermeable foam with a perm rating of 1.35 per inch thickness (a little less than rigid foam board).


Which specific Icynene product do you speak of?


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## Gary in WA (Mar 11, 2009)

C-200, the first one sited in post #53, supplied by you.

Not a vapor* barrier*; http://www.sprayfoam.com/mnps/fullthread.cfm?threadid=11908&mnforumid=2&mnboardid=5&startat=1


Gary


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## jackpine (Sep 3, 2008)

New photo update to project. It is coming along nicely, still a lot of work to do though. Redwood siding is a pleasure to work with.


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## kid (May 20, 2013)

*modding a 2x4 wall to 2x6 or 2x8*

i was thinkin i could just sister them to existing studs for stengh and more Insulation. cuase my house was built in the mid30s. what yall think?


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