2x6 24' on center
Last Post 04 Mar 2008 05:19 PM by ARdolson. 22 Replies.
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malibudUser is Offline
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08 Feb 2008 01:51 PM
Has anybody built w/ 2x6 24' on center I would like to but ive heard that the dry wall can come out wavy I was wonder has any one done this and had any experience good or bad ?
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08 Feb 2008 05:36 PM

The Arkansas plan called for building with 2x6's on 24 inch centers.  This method used a single top plate with the energy truss set directly over the studs.  I did not have any problems with this system in the 1970's.  One of the timesavers I used was to cut a "V" notch in the bottom of each 2x6 stud.  It saved the electrician from having to drill so many holes in the studs and also kept the wires down on the bottom plate out of the way of the 6" fiberglass insulation.  We made our own extended window and door jambs on site.  Today, with spray foam so readily available, I prefer 2x4's on 16" centers and double top plates. 

During that same period, we also used the Lee Porter Bulter envelope concept that involved double 2x4 walls set about 12" apart.  Both of these older systems would be costly with today's prices for materials and labor.

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malibudUser is Offline
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08 Feb 2008 10:27 PM
So for the price ... 2x4s on 16 " w/ Foam ?
AltonUser is Offline
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09 Feb 2008 06:46 AM
If I had to stick build a home today, I would use wood 2x4's 16" on center for the exterior walls, double top plates, 1" of Styrofoam or Thermax on the outside edge of the studs as a minimum and open cell polyurethane foam to fill the cavities between the studs.  If the budget allowed it, I would use closed cell polyurethane foam on the attic floor or open cell foam on the bottom of the roof deck.  With exposed metal roofs to the attic, I use closed cell foam.   

In the 1970's for passive solar homes we used 2x6 constuction and 6" fiberglass batts between the studs and up to 2" of Styrofoam outside of the studs.
 
In the future if I have to build with studs, that is, I can not use SIPS or ICFs, then I would prefer to use fiberglass studs screwed to fiberglass bottom and top plates and then insulated appropriately.  Fiberglass is light, strong, fire resistant and termite proof.  Maybe the company I am counting on for the fiberglass system will start production soon.

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malibudUser is Offline
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09 Feb 2008 08:56 AM
Ok thanks for the advice is the 2x6 on 16" for structure or wavy dry wall ?
AltonUser is Offline
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09 Feb 2008 09:05 AM
Malibud,

I use 2x6's on 24 inch centers.  No complaints on wavy sheetrock.  Maybe going from 1/2" up to 5/8" sheetrock would make the sheetrock stiffer on the 2x6 exterior walls.  In my area the code requires 5/8" sheetrock between the attached garage and the home on 2x4 and 2x6 walls.
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kicker_92User is Offline
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09 Feb 2008 11:08 AM

Don't forget to crown your studs. If you have the crown all facing in, or all facing out, the wall will be pretty much straight. If you just randomly put you studs in they will be wavy.

If it's a big deal, you could use a product like Timberstrand or LVL studs instead, perfectly straight everytime...

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10 Feb 2008 09:50 AM
Pick your studs as you build and set a side the crowned ones for cutting up into jacks or cripples. Pre drywall check your walls with a 6' straight edge in the center of the wall horizontally. Plain off any new crowns that point in. On interior walls, do the same and replace any studs that have gone wild with new ones. Generally this would be done pre-drywall and pre electrical.

Dave
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11 Feb 2008 09:10 PM
2x6 24" oc works well but I would recommend using 5/8" drywall for a more solid wall, and possible thicker sheathing as well. The suggestion above for rigid insulation on the exterior is a good one, giving you glose to R-30. You have to add blocking at the windows and doors, and may require additional nailers depending on your finish system. The suggestion to use spray foam is good, to, if the front budget allows. I have had remarkable results with it. In carefully aligned systems, with the joists and rafters aligning with the studs, a single top plate allows more insulation space and less material. Various green building groups suggest this for less framing material. A lot of buildiers prefer the double top plate for it's 'beefiness", giving you a more solid wall. Also, the double top plate gives ou a better drywall and crown molding trim attachment surface.
malibudUser is Offline
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12 Feb 2008 02:08 PM
Ok, Thanks for all the info, 5/8 dry wall seems a bit much and my hangers will be cussing my name. But what be more cost effective foam and 2x4s on 16" and 1/2 dry wall or 2x6 on 24s batten, insulation and 5/8 drywall ? The other question is OSB sheathing and off gassing... will the foam (open cell) prevent the OSB off gassing ? Iv'e heard to paint the inside w/ safe coat but that could be expenxive and time consumming What do you think?

Lastly does today's OSB sheathing still off gas ?

Thanks again for the replies
dc
blackdogarchUser is Offline
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18 Feb 2008 10:38 AM
You have to do the math yourself, from getting costs from area suppliers (number of studs, square footage of insulation, type of insulation, type of sheathing, type of drywall and square footage. (Will your drywall guys penalize you for 5/8? It is common in commercial constuction, so use someone else if they do). If you want cheap costs, 2x4 with R-13 fiberglass meets code (Northeast). Aded a layer for foam board to the exterior to reduce thermal bridging is a possible next step. Closed cell foam is more efficient. There are paints that will give you a vapor and air barrier, but off-gassing should not be a huge issue. Use 15# felt over the studs before sheathingif you are really woirried about it. Air quality on the inside from tight construction is more of a problem. (Use an air to air heat exchanger for air echange).
Don't forget, longer term operating costs will be offset by doing it better upfront.
malibudUser is Offline
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18 Feb 2008 02:53 PM
Thanks for all the replies but I am leaning toward 2x4s on 16" w/ foam or blow in and foam on the roof for sure. The reason being is that w/ 2x6 I loose about 25 SQ feet per 1000 seems like a lot .
DC
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18 Feb 2008 06:31 PM

Malibud,

Please allow me to modify the comment I made to you on 2-9-08 at 6:46 AM.  Change the words "open cell" to "closed cell" in every case.  I just returned from the International Builders' Show in Orlando where every expert and building scientist that I talked to encouraged me to use closed cell foam instead of open cell.  Open cell has a lower R value and it allows moisture and air movement which lowers its overall whole wall value.  At least, that is what I was told.

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malibudUser is Offline
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19 Feb 2008 08:39 AM
Here in Western NC Humidity can be a problem I was told not use close cell because of condensation plus close cell cost much more .
blackdogarchUser is Offline
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20 Feb 2008 09:25 AM
Humidity is a problem almost everywhere. We are near Philly and have a very humid summer, but hav esuccessfully used foam for a long time. . One reason for closed cell is to eliminate air and moisture migration to the cold surfaces that would allow condensation. The thickness of the application should be enough to eliminate a dew point on the interior surface in the sumnmer and the exterior sheathing in the winter (inside surface). Talk to the vendors or the main company for advice, your local building officials or check the codes for the recommended R-values. (I am always amazed how people turn to anecdote and conjecture before talking to the manufacturers or local installers/vendors).

Also, control your indoor humidity (rule#1) by properly venting ALL fans and using an air-to air heat exchanger or perioding venting in a tight house.

Lastly, 25 sf is not all that much, a 5x5 area, in the scheme of things, if the 6" wall gives you an advantage. If you are using foam, there is no advantage except a vsual one if you like thicker window sills, or structural if you want greater bearing capacity (usually no need for a 2-story house). Check with an engineer or your building department about 2x4 24" oc. It may be a bit shy of good structural practice, unless you very carefully align all the rafters, joists and studs, etc. There will be no slack in that system.
AltonUser is Offline
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20 Feb 2008 09:43 AM
I was told at the International Builders' Show in Orlando, FL that that the closed cell polyurethane foam should be at least 2 inches thick to act as a moisture barrier.
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blackdogarchUser is Offline
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20 Feb 2008 10:15 AM
And as areasonable level of insulation. Don't forget, insulatoin is as important for air-conditioned spaces as heated.
malibudUser is Offline
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26 Feb 2008 10:52 AM
Ok back with cost comparison 2x6 w/ blown cellulose same as 2x4 w/ closed cell foam cost wise ... A little better r value w/ the cellulose but better air control w/ Closed cell foam and make s the wall strong and ridged of coarse 2x6 walls are more beefier. I have to tell my draftsman what to put in this week any suggestions?? it is a 2000 sft house in western carolina
thanks
d
blackdogarchUser is Offline
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04 Mar 2008 09:37 AM
The 2x4 wall 16" oc is probably beefier, less flex in beween the studs, but not a huge issue. But there are more thermal breaks (more studs). Another wrinkle: use 2x6, 16" oc, 2" foam and you install 3 1/2" R-13 in addition to the foam. You get the advantage of less framing, thicker walls for a roughly R-26+ wall insulation value, looks nicer around the windows. I would suggest again, the thicker drywall, or one of the more rigid panels some manufacturers have for this kind of application.

Don't forget to meet or exceed code requirements for the roof, almost more important than the walls, and the floor. Foam the window edges, caulk the wall plates etc. Good luck.
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04 Mar 2008 09:59 AM
Posted By malibud on 02/08/2008 1:51 PM
Has anybody built w/ 2x6 24' on center I would like to but ive heard that the dry wall can come out wavy I was wonder has any one done this and had any experience good or bad ?
mailbud;

33 years ago when I worked for a wall panel pre-fab company,  that was our "energysaver" wall system with R-19 insulation.
Drywall @ 24" oc work better on steel studs than wood. Its not the drywall that wavy, its the studs behind it.
 a good reason wood framing is preferably @ 16" oc is beacause of bowing and twisting studs. Never a problem with steel!

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