2x4's vs 2x6's?

That method came into popular use in the late seventies. Some locales still depend on it even to the point of pushing it via building codes in spite of the fact that since then, much better ways of adding insualtion and quality to the house have been developed, including spray foam such as Corbond and breaking the thermal bridging with foam sheets over fibreglas.

The originators of 2x6 style framing sold us on the idea of changing to 24" OC instead of 16" OC to keep total lumber cost similar but other drawbacks exist with such wide spacing of studs, such as wavy walls.

Most knowledgeable builders understand there is no cost to benefit ratio by using 2x6s over 2x4s. None.

In fact, using 2x4s can be cheaper AND more efficient as far as insulation goes.

First, if one uses 2x6s one not only increases the cost to insulate, one also increases the cost in windows and doors sicne jambs must be ordered or constructed to fit a 2x6 rather than a 2x4 wall.

Second, 2x6s may add an increase in depth for and to include a 'thicker' insulation but this insulation alone will not insulate a home 'better' than a 2x4 wall with proper treatment...

Here is how most 'pros' do it:

-Construct 2x4 walls. (There is no less structural difference between that and 2x6) construction...

-Add 1 " of foam insulation on the outside of the house. This creates a thermal barrier that increases the insulating factor much mor greatly than simply increases the wall dimensions to 2x6. This also decreases the chance for condensation to form in walls. Eliminates the need for housewrap, builder paper, or other secondary weather barrier beneath siding.

- Eliminates the need for another and more costly 'backer' beneath vinyl siding...

Only 2x4 construction for me...with 1" foam insulation over sheathing on the outside. Compressed R-13 on the inside.

Thanks for the info, guys. Homebuild, I have read that 2x6 walls allow for an R value of 21. As far as I know, 1" foam typically has an R value of ~5. When you say that 2x4 walls with 1" of foam on the outside "increases the insulating factor much mor greatly than simply increases the wall dimensions to 2x6," is that simply because the exterior foam is contiguous, as opposed to the batt insulation which is broken up by the studs? By rough calculation, 10% of the wall by length would be un-insulated with 16" OC construction, so that R21 with the 2x6 would average out to more like R19, all things being equal.

Exterior foam creates a thermal barrier between the studs and the external environment.

Not only does that create a warmer house than using batt insulation alone, it greatly lessens condensation problems is walls.

The reason is that by insulating the sheathing over studs, you can usually keep the stud spaces above the dew point so that condensation will not occur.

Foam exterior sheathing also eliminates convection currents within stud spaces for more uniform insulating tempertaures. This also reduces the potential for condensation.

Condensation in fiberglass reduces the ability of fiberglass to insulate.

Therefore foam over studs is much more effective than just fiberglass between studs alone.

But in all fairness, you could get a greater insulating factor using 2x6s with exterior foam compared to 2x4s with exterior foam, but the cost to benefit ratio may still not be there.

Thanks for taking the time to explain this to me in so much detail, Homebuild. When the time comes to build my new house, I'm certainly consider this method.

Good info.

My wife likes 2x6 walls, it gives the window area more room for her cat to sit and look out the window

M C

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How is this accomplished? We are building a home with 1/2" OSB, and if we add 1" of foam, then our hardiplank siding will stick out beyond the edge of the brick ledge trim at the outside perimter of the windows. Can you get a deeper brickledge?

Also, if you use foam instead of a house wrap, do you install the foam 1st and the windows second? Would this not cause the windows to be nailed into foam causing an unstable nailing surface since the foam may get futher compressed with time?

It is possible to nail window flanges over the foam if you are careful not to nail too deep and compress. Some builders use a wood shim directly behind the window flange.

If you are using brickmold on the windowsfor acasing, the load is spread out enough to not compress the foam. Brickmold is for bricks though. a Casing is better for Hardi, IMO.

In warm climates it is best to add this faom on the exterior, but in cold climates, it is best to use it on the interior side of the wall

Excellence is its own reward!

If you do not plan to use a house wrap over the foam it is also a good idea to tape the joints between the foam panels to prevent air infiltration through the cracks between the panels.

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When building a two level house with the first level overall ceiling height being 12' is 2"x4" construction strong enough to support the weight?

No structural improvement!! Give me a break. I have seen tall 2x4 walls in houses move when the door shuts! I have also grabbed the bare studs mid construction and felt that I could cause major damage if I shook them.(Taller wall of course.) I could not tell you how many 2x4 studs I have seen break when someone climbed up them during construction. The statement is just absurd. Exterior walls will obviously have a better R-value. It retains the interior temp better. I know people that had 300 more square feet and a house built with 2x4, averaged $500 per month higher utility bill than my house with 2x6. The biggest thing you can do for your house is make bigger eves. Foam on the exterior? Maybe for wind block! It has less than a five R-value! I also have a house built during the war out of 1x3's. Is not bad to heat and cool. Pretty incredible but has no insulation in the walls. What blocks the wind is the most important aspect of R-value.. It is like water and will find the weakest point. The war home was wrapped in tar paper, much better than ty-vec in my opinion. You have to stop the air-flow. So I was just aggrevated to read such a response, what I do know is that the costs of different insulation can be huge. Why are ceilings covered in deep insulation over 2x6? Better r-value.. My opinion..

Amen! Been through all the same. I own a duplex built in desoto ks and it was later moved from the ammunition plant from the war. The trusses and ideas they implemented are awesome. I was told by a vet from the area that they were designed to have a five-year life span! It's still standing. I have lived in a house with 2 x 6 walls that I remodeled. Lowest utility bill ever! Also the biggest house I've ever lived in. Walls were covered with like a mil. 4 plastic not tyvek. I think life experience tells more than some young buck with a bunch of contractors throwing things together!

Amen! Been through all the same. I own a duplex built in desoto ks and it was later moved from the ammunition plant from the war. The trusses and ideas they implemented are awesome. I was told by a vet from the area that they were designed to have a five-year life span! It's still standing. I have lived in a house with 2 x 6 walls that I remodeled. Lowest utility bill ever! Also the biggest house I've ever lived in. Walls were covered with like a mil. 4 plastic not tyvek. I think life experience tells more than some young buck with a bunch of contractors throwing things together!

It is plain ignorant to suggest that a 2x4 stud has the same structural capacity as a 2x6 stud. Simple mechanics of materials.

To piggyback on the last comment, a 2x6 has exponentially higher bending capacity, it is stiffer (resisting out of plane wind loading) and also much higher axial capacity. A 2x6 stud in a wall with a 12’ plate height has over twice the axial capacity as a 2x4. When comparing the 2, its not always 1 to 1.

Homebild is wrong on most of his comments but one that really is way out there is compressing insulation, never compress insulation, it lowers the R value and can cause problems with the drywall.

structural capacity of 2x4 vs 2x6 from a structural engineer:
The cross sectional area of 2x4 @ 16 and 2x6 @ 24 is almost identical. So for direct compression not considering buckling they have the same capacity. 2x6 walls have a higher capacity for bending, but that isn't actually the function of most walls. So when people say they are structurally the same they are referring to the final product in direct compression and it is a mostly correct statement.

if you worry just have 2x6's at the same spacing as you would with 2x4's the fact is you will have less warping and structure issues 10 -15 years down the line, a 2x4 is nice but the fact is a 2x4 is not what it used to be... it's more like a 1.5x3.5

A couple of things. Homes started being built in the 70’s using 2x6’s so we could increase insulation levels. The energy crisis was on and higher insulation levels reduced our heating costs.
Unfortunately, history has shown us that old structures made from 2x4’s are just as strong as homes built today with 2x6’s. One of the reasons, is the difference in nailing. In the old days, when we framed with a hammer, we used spiral nails that we drove in at an angle. Today, we use pneumatic nail guns. The nails are straight, not giving them much grip. They are also driven straight in. Rarely are they “toed” in.
As for insulation. We now know that when fibreglass insulation is installed, we get air pockets. The effective R rating of fibreglass insulation at 32 degrees is zero.
I remember a study in the mid 70’s in Minnesota. They tried something called “super insulating” using different techniques. Their most efficient wall style was a double wall with 2x4 construction. Essentially, they framed their exterior walls. They insulated them with fibreglass. They then covered the inside with foam board insulation. It was the cheap white foam, not the rigid boards we use today. Then they built another 2x4 wall against the foam insulation, being careful to have the studs offset. Their intention with this was to reduce as much convection of cold through the studs as possible. It worked. They were able to heat the house with electric light bulbs. There as no draft or air infiltration. Unfortunately, it meant an airxchanger needed to be installed. Today’s furnaces do that for us.
Hope that helps
Sean