2 x 4 vs 2 x 6

[flyingvan]

Explain to me how cutting down trees 'you don't need' is the problem....If you believe the man made climate change stuff, atmospheric carbon is to blame.  (I think this is like debating the life cycle of leprechauns, but I'm just using Al Gore's own arguments here) so ignoring the aesthetics of trees in the vertical position---which I think we'd all agree is a good thing--- if I grow trees, cut them down, bury them, and grow new fast growing trees in their place, haven't I pulled carbon out of the atmosphere and sequestered it? 
Your article there is incorrect---when I studied forestry at Humboldt we actually looked at carbon uptake of young trees versus old.  Young trees need it for leaf and wood production---the older the tree gets, the slower it adds wood.  There was also a significant difference in a young tree's ability to fixate subsurface carbon compared to old growth.
Another incorrect assumption you make is, the ultimate fate of a home's lumber is burning, thus re-liberating the carbon into the atmosphere.
Of the 270,000 homes torn down annually, a little of that material gets recycled, but most ends up in landfill---estimated about 1 billion board feet worth of lumber, buried.  Sure, some of that will be re-released as Co2 through microbial breakdown---like forests have been doing since there were forests. 
True, there's a negligible increase in hydrocarbon consumption with bigger material.  Offset that with the R-21 I get instead of the R-15, without adding a layer of some foam product.  You can't convince me a house built with stronger materials won't last longer, and a house that stands for 100 years will have much less environmental impact than three houses that last only 30. 
  I couldn't find any data supporting what you said from the AWC---do you have a link?  All the comparisons I can find compare 2x4 walls 16" OC with 2x6 walls 24" OC.  I wish they'd also through in 2x6 16 OC.  I suppose at some point the height of a wall in a high wind area will fail by blowing over, remaining intact the whole time...If a wall in the wind is well supported top and bottom, though, the center will be doing the moving---and my money's on the 2x6 wall flexing less, avoiding the creaks and nail pops over time.
  (The decision was easy for me---I was required to have these seismic hold downs and they were required to be anchored to 2x6's)

[MountainDon]

...a house that stands for 100 years will have much less environmental impact than three houses that last only 30. 

the above is quite relevant and, IMO, a big reason to start correct at the bottom and do it right with a foundation that will be able to go the distance. )You know where that's leading but I'm not going to beat that horse today.) 

[alex trent]

So, you say that houses built with 2x4 will only last 30 years?  There are millions on millions of example that defy that fact.  Even in relative terms there is nothing factual to say that a 2x6 house is  more likely to last three times as lo as a 2x4 house...or is there?

FVan...I thought about the chart in AWC and the codes....your codes must be less stringent (at least in your area) as they permitted something even the wood people say is not permitted.

Here is the AWC link.  I looked at it a while...am I missing something?  Looks like the only real difference is not permitted to use 24" spacing on a two story building.  As you have alluded to, there must be a lot of other things to coping with high wind than stud size.  Sounds reasonable when you think of the house and how it reacts to wind and the relative strength of wood (even 2x4) on that axis.

As for you concern about nail popping due to flex, you have any facts on the relative flex in 2x4 and 2x6 in walls.  I know the flex of a single piece differs, but in a wall with multiple studs close together is there really any difference that has practical value.

As for your words on carbon, I'll pass on debating the big picture.. What you learned at Humboldt State about big trees and small trees and the relative carbon uptake is correct....up to a point  One of the main reasons for that is that small trees have a much greater leaf to mass are than larger trees and it is the leaves that use the carbon.  But the rate needs to be multiplied by the tree leaf mass to get to the total amount of carbon used.  So a small tree with 1/10,000 the leaf mass and 2x the rate is still way behind in carbon uptake. Your other stuff suffers from the same disconnects in facts and there are other places to debate that stuff.

The point is not to use more than you need for environmental as well as structural integrity....not just woo, but oil, water, etc.

[Don_P]

Wood sequesters carbon if you bury charcoal, otherwise it cannot be honestly considered to offset the burning of fossil fuels, those are two different carbon loops. The arguments otherwise are pcbs.

A 2x6 wall is stronger than a 2x4 wall. I've built engineered tall 2x8 walls with all framing, sheathing and connections specified, there is a place for each.

Wood is renewable, most forms of energy are not.

[flyingvan]

 Ah---Here it is.  it took me awhile to remember where I found the info I needed for my wall.  I see the disconnect now---you are only comparing load bearing walls.  My roof is supported by three columns holding a ridgepole.  My tall balloon framed wall is technically 'non load bearing'---but it does face the wind.  We've had 100 mph gusts here, that's a lot of Bending/axial load....
http://www.awc.org/pdf/WFCM_110-B-Guide.pdf  (I couldn't see the link on your post)
  Here's two of the columns

 

And here it is with the ridge pole in place



  I used this same AWC reference when drawing my plans.  Scroll down to Table 5, page 12.  According to AWC's chart--for a non load bearing wall in a high wind area, for #2 grade lumber 16" on center, here's what's allowed--

2x4's max stud length 11'5"
2x6's max stud length 18'5" (Mine are 17' 7 1/2", 18 even with sole and double sill)
2x8's max stud length 19'9"

[alex trent]

 
I figured there was a reason whey you could (would) do it....

Good stuff to know.

I also looked at the 130 mph chart on AWC...that also works with 2x6...so you can take even a bit more!

I take it the back (shorter) wall is classed as a load bearing wall.

On a more general note, from what you say, having a ridge beam means the corresponding wall(s) are classed as non-load bearing for this purpose. I have a guy here who wants to build a shed type roof  16 feet high in front and 12 in back...kind of an observatory...30 x 18 feet.   So if it works like this he can use 2x8 in front and go all the way up as long as he uses a ridge beam in the front...probably three posts to support it, maybe 4

[Don_P]

Walls that rafters bear on are load bearing irrespective of the ridge configuration. Gable endwalls are typically considered to be non loadbearing. If the roof is a typical symmetrical gable the sidewalls each bear 1/2 of the roof load. If there is a ridgebeam that beam bears 1/2 the roof load and each sidewall bears 1/4 of the roof load. For a shed roof each sidewall typically bears 1/2 of the roof load. 9'9" max height without design @110mph in the WFCM. Tall slender posts need design. Do read the design concepts and foundation section carefully.

[MountainDon]

Thanks Don, you typed faster than I and expressed my thoughts better.   

[MountainDon]

A ridge beam is essential when designing rafters for vaulted / cathedral ceilings with a gable roof and the designer does not want to incorporate rafter ties on the wall top plates. The ridge beam then structurally converts the gable into what amounts to two shed roofs... all gravitational forces go straight down. Standards for heights must be followed or calculated on a case by case basis.

That 16 foot wall would need design analysis it would seem. Maybe another topic as well.

[Ndrmyr]

Perhaps this is beyond a simple "more is better" argument.  This I know, for years when I DIYed something, it has been my inclination to invest my labor savings into either material upgrades or in many cases, the tool(s) needed to do the job.
Sure, if we were Johnny Lunchbox and were buying a fully financed subdivision home that stretched our monthly payment to the breaking point, every upgrade is one we can ill-afford since we are already buying more house than we can afford.  Certainly this was the case in the pre-housing bubble buying euphoria.  Where someone didn't flinch at the $22,000 Cherry Kitchen upgrade.  Really?
I truly do question the longevity of much modern construction.  A preponderance of OSB sheathing, I see houses built with no wall sheathing except for a couple sheets at the corners, nothing but vinyl siding on top of the house wrap.  A burglar with a cordless sawzall can be inside in 90 seconds.  Can modern construction techniques be better? Sure, if they are utilized.  Are trusses, hurricane clips, modern construction adhesives better...yes.  If they are used. Too many short cuts.  What is the life span of my 6x6 post and beam infilled with 2x6 walls screwed into sill and top plates, sheathed with 3/4", interior sided in 1/2" OAK with a metal roof?  I suspect in the 200 year range, longer if a good roof is kept on it.  I couldn't have afforded it if I was paying a contractor. But, I COULD afford it with my labor and materials acquired at auction.  Is the 3" of closed cell foam in the walls excessive?  Perhaps.  Still, I was building a multi-generational structure that will be handed down to children and grandchildren.
Frankly, there isn't a real right or wrong answer.
If I am building for my lifetime and maximum energy efficiency, I think 2x6's are the way to go. If my structure is seasonal, and may be sold in my lifetime, 2x4's are good enough.  Build to your need, and....desire, and.....ability.  And be secure in your decision.

[flyingvan]

Couldn't agree more.... A lesson I learned from building my first house was, for just a little more money and a little more effort, there's a way to make every step a lot better.  Take your OSB example---I could have hired an engineer to figure out where I needed shear panel and put up the minimum, or for less money I could just shear the whole thing.  Whole structure is stiffer and slightly more protected.  Entire house wired with 12 awg instead of 14.  Copper piping, type K (OK you pex people, might be a great product but I know two cases where mice chewed through the stuff)
The difference in cost is only in the hundreds and I see my time in building/repairing as more than that.  I'm building ONE house, so saving a little here and there doesn't really pay for part of the permit fees.  However----if I were building 4,000 mcmansions, all identical except for the color of the granite countertop, every penny I save means another $40.00 profit so I'm going to build to the very edge of the minimums, even invest in engineering to show me where I can save more.  As a firefighter when we're done putting out a house fire we'll tear  out drywall lookiing for fire extension---it's an eye opener how cheap houses are built.  Roofs barely support their own weight.  I've seen type 'M' pipes.  HVAC ducting takes crazy sharp turns with flex pipe that could never be cleaned. 
Houses are priced according to size and location though, quality of construction is a minor factor.

[Alan Gage]

While I'm all about saving energy I'm not convinced there's that big of an advantage jumping to 2x6 walls alone. If you look at the actual R value of a 2x4 and 2x6 wall (taking into account the framing) they're both considerably lower than the stated R value of the insulation (R9 and R13 respectively if I remember right).

My dad and I are remodeling an old house and he wanted to add furring strips to the 2x4 studs to bring them to 2x6. I ran some rough heat loss calculations and figured that even if the price of natural gas doubled the heat savings would be $55/year. This is in a climate similar to Minneapolis. So yeah, it will eventually pay for itself, but it's not a huge jump and I doubt it will feel any more comfortable in the house.

We're doing the furring strips, BTW. His house, his money. He can do what he wants.

Alan

[alex trent]

I generally agree with build it strong and don't wood about a few bucks here and there. I see that too...saving 10 bucks on nails or such.

But not every big house is a poorly built "MacMansion".  Just as we like small houses, some like um big.

And a lot are very well built.

Take a look at Outer Banks of NC....they stand to wx that most do not get. 2x4' studs at that.

It's nice that some of us on here build build great and small and strong, but denigrating others does not make our work better.

[flyingvan]

The point I'm trying to make is, as individual builders it's in our best interest to build well with good materials.  The major developers can and do cut many corners. 

[flyingvan]

AS far as whether a 2x6 house will outlast a 2x4 house---if that were the only factor different between two otherwise identical houses, probably little difference.  But if everything is equally beefed up---foundation, sheer panel, roof decking, wiring, subfloor, waterproofing, copper, etc---all bumped up to the next level, I believe that it makes a big difference.  (Not as big a difference as ongoing maintenance though)

[alex trent]

We pretty much agree. Most mass produced houses are built sloppy...at beat finished poorly. At worts structurally not too sound. I goes that last point is the big saving grace for code sand inspectors, et. At least they keep it to some minimum level.  I have no doubt you are right, that many of them will see problems in a relatively short timespan.  But the way the housing market was is that many people saw the house they moved into as a short term investment to soon flip and make money and move "up".  Likely some of that has changed.

I would guess that most people do not really know what needs to be beefed up and what is OK at the code level. Be good to see a prioritized list from what you really should beef up to the lower priority options.  Maybe even some cost difference. For instance i put 12 ga wire in my house and not really sure why when here 14 is the norm...I think just afraid of fire.  The cost was a couple of bucks.  Just did it, but be nice to have a must do vs. could do list for those who don't know where to start.

The point is it is better to overbuild something that needs it more than something that you could live without.  My house is a bit of an anomaly but since built an analysis and inspection by two engineers tells me I could have saved about 2k on the wood.  My wood is very expensive here, so that likely does not apply everywhere...but I use it as one example.

[flyingvan]

Around here, 2K is about one house payment (actually I think the average is higher than that)  I think it's a good move to use 12 awg wire as there's less voltage drop.  The yin to that yang though is cost, and the struggle to stuff those 12 g pigtails into a box.  14 g is a lot easier to pull too.

  I kind of look at builds as a spectrum.  At one end, you've got Imhotep and his pyramids.  A bit labor intensive, but still standing after a few millenia.  For a little less labor and a quicker build with less environmental impact, you could pitch a tent squarely on the other end of the spectrum.  I understand the attraction to building from a minimalist perspective, but it seems for the amateur owner/builder, tending towards the stronger materials is good practice (Yes---especially starting from the foudation).  To me it adds a margin of safety, especially for those of us without an engineering background.  So anytime someone asks, I'll tell them 2x4's are fine but 2x6's, in my opinion, are worth the extra money. After having to lift two houses off of piers to pour a perimeter foundation, I'll steer people away from piers when I can.  Single glazed windows, T1-11 siding, (failing at my work station right now!) same thing.   (Actually I'd never build with roof trusses either but that's just because they kill firefighters.  Besides, having a big heavy timber at the top of the house holding the roof up just feels better to me)

[grover]

My intention when starting this was the question around problems or issues that would come up that I'm not thinking about.  I think a 2 x 4 house is strong enough when built correctly.
My thoughts of going with 2 x 6 exterior walls was for the extra insulation possibilities.  I don't think I can afford to do the spray on closed cell stuff but I was thinking 2 inches of the blueboard type stuff with great foam around the edges to seal out air.  Standard 3 1/2 inch fiberglass on top of that.  Don't know what the R value is but should be good.

[MountainDon]

.... I was thinking 2 inches of the blueboard type stuff with great foam around the edges to seal out air.  Standard 3 1/2 inch fiberglass on top of that. 

Yeah, things sort of ran all over the place after a short while.
3 1/2 finberglass = R13
2 inch blue foam = R10
plus you pickup a little extra with the rigid foam being full coverage, over the studs.

The ideal installation would stagger the seams of two layers of foam but that does cost more.

[grover]

Mt Don, I think you misunderstood the way I was planning to install the blue board.  I was thinking of putting the blue board in between the 2 x 6's and filling the rest with the fiberglass.
Were you talking about full overlay of the blue board on the 2 x 6's?

[Redoverfarm]

grover the way I understood him was that if you put two layers and stacked them one on the other and broke the seams at the same location there would be a void that air could penetrate at that seam.  By staggering the seams you would not have that void from the outside to the inside.  But if you run full sheets from the floor to above the upper plate there would be no seams.  But most likely you will piece some.  Just make sure that the seams from the 1st sheet and second are not in the same place in the cavity.

[MountainDon]

I was meaning building with 2x4 framing. Filling the wall cavities with R13 fiberglass. Then sheathing the exterior with two 1 inch layers of R5 rigid foam. That breaks the stud thermal "leak" as John pointed out. Insulates and air seals well.  Cutting and fitting rigid foam in stud bays is not my idea of fun. Sheathing the exterior with foam does mean you need to do some special things at doors and windows. The buildingscience.com website has info as do some other sites. Depending on the climate 2 inches of exterior foam is all that is required to make the inside face of the foam warm enough to prevent condensation in the wall.

What climate zone are you?
Climate zone map info

I think up to climate zone 5 would be covered by 2 inches of foam.
This is for walls with f-glass or other batts in the cavities and covered on the exterior with rigid foam insulation. IF the foam is too thin for the coldest expected temperatures there then is the danger of the inside face of the foam surface getting cold enough for moisture to condense.

There's more info here someplace if we need it.

[flyingvan]

If you stack R10 over R13, do you add, or multiply, the R values for the total R value of the wall?   Would it be R 23 or R 130?  Or some other number depending on the space between the two?  How do I figure my R value of the wall if it's a layer of caulked Hardie board, tyvek, 1/2" OSB, R21, then 5/8" interior t&g spruce? I can find R values for all those things, I don't know how the cumulative works though.  Seems like you'd multiply if every layer keeps a percentage of the heat in (or out)

[Don_P]

Additive... but I've never actually tried your method with the BO 
I've had plans where they were adding everything, there is a boundry air layer with some fraction of an R, the sheathing, etc. ResChek is another method.
From our PM, I haven't found my windspeed/pressure calc, I lost a few in a hacking but did get the formulas to work longhand, just need to reprogram it. Meanwhile wind pressure tables are in chapter 3 of the IRC.

[MountainDon]

Yes. Simple addition. Except it's not so simple when there are studs covered by foam, for example. That's why the IRC will have a qualifying wall listed as R20 or R13 + R5. The first number (R20) being the required insulation installed in a stud wall cavity and the 13 + 5 being R-13 cavity insulation plus R-5 continuous insulation or insulated siding.
http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm

REScheck is a cool tool. It can be fun and educational to work with. I like it as it allows trades to be made; adjust window areas, make one wall thicker, and so on. Our state (NM) requires submission of the REScheck data sheet along withthe building permit application and drawings.

A qualifying air space can add R 1.7 if I remember rightly. But that's really only good for additional radiation value as in having a 3/4" air space between the exterior siding and a foil faced foam sheet. It doesn't do anything when the sun goes down. I'm re-doing our home's east and south facing walls with 2 inches of exterior foam as a two to three year project. Teo layers of foam; XPS next to the sheathing and polyiso with afoil face on top of that; 3/4 air space and then lap siding. I have no empirical evidence but the room I did that to in spring seemed cooler over the summer and now that cool weather has hit warmer than before. New windows helped too. And there I go again running off in another direction....