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questions about 2x4 vs. 2x6 framing

dc_'s picture

I was browsing through the Building in Mixed Climates book and noticed the author(s) recommended to use 2x6's on 24" centers. He said there is the same board footage, but you use 30% less material/sticks.

How would one go about estimating how much wood is in the walls of a structure? So I would know that a 40'x40' build using 2x4's will need this many sticks and a 40'x40' building using 2x6's will need such and such.

Is there a framing book I could read that would explain cost/material estimation for the framing package of a basic home/structure?

One reason I want to know how to do this is so that I'll know how to do it. Sure, a computer program can crank it out, but I would like to know how to it by hand or using one of those builder's calculators if it would help.

Any other tips?



(post #89057, reply #1 of 38)

run a calc for a 20' wall section for each example .. then extrapolate from your sf or lf answer...

try a few permutations : (lots of windows vs. no windows)...

thsi will start you on unit price estimating.. but most of what we do in remodeling is a combination of unit pricing and stickbystick...

(post #89057, reply #2 of 38)

That author makes a general statement that is true only about half the time. As Mike said, corners, windows, and doors make the figures vary from one job to the next. The way to be accurate is to count them. You need to figure for waste too which is a guess.

2x4 plus foam board is far better construction in most cases.

Good luck

(post #89057, reply #3 of 38)

absolutely... 2x4 @ 16" + foam board is what we use for energy wall too....

(post #89057, reply #4 of 38)

If I remember correctly, you can find the number of studs in a wall by multiplying the length of the wall by .75 as long as its on 16 inch centers with no doors or windows and that will be a ball park figure. Generally speaking you would figure 5% for waste to answer someone elses question about that.
As far as using 2x6 walls on 2' centers, you better check your local building codes before you try something like that. I think a better bet would be to go with the 19 3/16 (black diamonds on your tape measure)inch layout. You would have to lay your sheathing down since the sheets would only break on the studs every 8 feet, but I don't think that would be a problem as long as you stagger the joints like on a sub floor. Once again, you would have to check your local building codes before you tried that too. Hope this helps.
EDIT: One more thing. About foam board, builders use foam for a tax break, thats it. Its cheaper then plywood by a buck or two a sheet and the government gives them a tax break for using recycled materials in new construction. The R value of a sheet of 1/2 inch foam is only a "3" and if I'm not mistaken, the R value of a sheet of OSB (or Ox Board) is a "5." If I'm wrong on that last tid bit of info, please correct me.



(post #89057, reply #5 of 38)

estwngr... just a misplaced decimal point among friends ..

osb is .5 and 1/2" foam is 3.0

but we're talking about 1" foam

and we use it for energy conservation... not for no stinkin tax break

now .. if you're talking about the Energy Star program.. that 's a pretty good program...

(post #89057, reply #6 of 38)

Question for Mike Smith: Mike, What are your reasons again for placing the rigid insulation on the inside rather than the outside? I know this is your practice, so I'm asking you. Also, do you add the insulation to the door and window reveals as well?
Thanks, David

(post #89057, reply #7 of 38)

My ROT for 2x4@ 16" is to take off a stud for each lf. Interior and exterior walls together. This gives me enough for jacks, corners, cripples, etc. I do my bottom, top and top top (strenght) plate by lf x 3, and then throw in x number of feet for braces and such. If I can convince the others working on a job that studs and 8' 2x4 aren't the same I ussually have about the correct number of stud, including waste.

2x6 @ 2' o.c. use the 0.75 that was mentioned above and you come real close to the actual count when you throw in door, windows, corners. tees, etc.

Works most of the time for me.


(post #89057, reply #8 of 38)

So the 1 inch rigid foam board instead of OSB on the exterior? And this is good on corners, too? The whole house?

Our current house, the framers used OSB only on corners and foam everywhere else and it was a PAIN to hang the Hardi-Plank siding where we were trying to nail to the studs. I guess we need to get better at nailing (-:

Am I correct to assume that if half-inch foam board has an R-value of 3, then one-inch has a 6?

So, asside from possible building code restrictions,
using 2x6 doesn't get you much?


(post #89057, reply #9 of 38)

well, we used to put one inch foam on the outside...but it was a PITA... had to block everything... also it put the highest R-value on the exterior... moving the dew point towards the outside...

it slowed down the drying in phase of construction...

it reduced the racking resistance of the plywood sheathing...

and it put an additional vapor barrier on teh exterior... fighting with the vapor barrier/ vapor retarder on the interior....

now , with foam on the interior.. all we have to do is furr the interior of the exterior walls.. this moves the electrical devices 1.75 inches away from the exterior sheathing so there is more room for insulation BEHIND the electrical devices...

here's the choices for an energy wall (cost being a consideration.. i mean we can do double wall or other exotic things ..)

all assume 1/2 " sheathing on the exterior

1) 2x6 24" OC
2) 2x4 with foam on the exterior
3) 2x4 16" OC with foam on the interior

my choice is #3...
specifically... from out to in...

1/2" ply... 2x4 studs @ 16" with 3.5" denspak cellulose

1" EPS foam (density of 2 lb/cf)

horizontal furring @ 16" OC

1/2" blueboard / skimcoat...

since 1976.. we've done 2x6, double wall, exterior foam and now interior foam.. so ..our energy wall has been an evolving thing..

(post #89057, reply #10 of 38)

I don't do hardly any framing...but like the sounds of your system. I'm wondering about the horizontal furring under the blue board. Is this for an extra dead air space to increase R-value? Would there be problems attaching the blue board directly over top of the EPS (screwed thru to studs)?


(post #89057, reply #11 of 38)

For a 2x wall @ 16" centers I use 1 of 2 methods. The 1st is to multiply the lineal footage by .75 then add 4 studs for every window and door. this is the most time consuming way to do it. The 2nd is to multiply the lineal footage by 1.25 for a larger project. Then multiply the lineal footage by 4 for the plates and blocking. Add in the bracing for wall and you will have the material you need for the job. Check your local codes for 24" centers on load bearing walls


(post #89057, reply #12 of 38)

stray.. i've seen the blueboard installed directly over the foam board.. even 1" foam..

... i didn't want to do it that way because of trim & electrical device problems..

the 3/4 furring gives me:
all the nailing i need for trim,
it reinforces the EPS ..
makes an easy target for the board hangers...
helps prevent crushing of the foam...
and gives the owners some place to hang pictures...

(post #89057, reply #13 of 38)

Mike, I've always gone straight over the foam with the rock but I like your furring idea.

Been on the road a little.

(post #89057, reply #14 of 38)

I don't know about the rveals. Probably not. But the foam board is added on the inside:
1) because foam board is a good vapor barrier and adding it to the outside could, assuming another good vapor barrior wasn't added to the inside, cause condensation in your insulation.

2) because many exterior sidings are easier to attach directly to the sheathing as opposed to having to go through the foam board first.

(post #89057, reply #15 of 38)

minor clarification,
because it is an insulation it is unlikely to 'cause' condensation but it does belong on the inside. But the reason is that it also functions as a vapor stop so it will hold water vapours in the wall, leading to mold and rot.

(post #89057, reply #16 of 38)

2X6 @ 24" is a bad idea. I know because I lived in a house with that construction for 15 years before I tore it down. Insulation, absolutely, the sole benefit. Flexy, even more so - expect sagging above and racking below. Every time you want to mount something into a stud, the next stud isn't the 16" away the product expects, so get the molly bolts out.

If you really want insulation and strength, look into SIPs. 2X6 SIPs are R-24 (compared to R-14 for a 2X6 stick wall) and absolutely will not rack, twist or sag. Even 2X4 SIPs will outperform a 2X6 stick wall.

(post #89057, reply #17 of 38)


RE: electrical boxes, are you poking the wire
through the foam ( wiring stapled to sides of 2x4 studs
and then attaching the strapping, and then cutting a
hole for the box and slipping it in and nailing the box
to the strapping?

Or are you using the airspace created by the strapping as
a chase for the wiring?

Just curious and trying to visualize the steps.


(post #89057, reply #18 of 38)

* that installation.. we used a 4" box with a side mounting strap.. the box had a 1.5" plaster the surface of it stuck out 2.25 " from the face of the stud.. (1" foam, 3/4" furring + 1/2" blueboard..

we mounted all of the boxes in the exterior walls, the electrician wired them...

we installed the 1" foam.. and the horizontal furring after the wiring was complete...

(post #89057, reply #19 of 38)

It's interesting how different these methods are from one part of the country to the other. Out east, the furred blueboard is common.

Here, I've seen it on ONE house. You can't find a plasterer in Wisconsin to save your life.

We just use 2x6 on 16" centers, OSB or ply sheathing. Simple.

If you want to compare the cost of doing 16" vs. 24" o.c. I think you'd be surprised to see how little you save to have the future inconvenience of 24" spaces for the reasons others have mentioned.

I have no doubt that Mike's method is BETTER. And this is FINE Homebuilding. So, maybe to take it even further, you could use resilient channel under the blueboard. But I'm not trying to spend more time and money on the walls. That's why we do it this way.

I'd love to learn plaster. It's fun just to watch those guys on TV, which is as close as I'll ever get here!


(post #89057, reply #20 of 38)

dawg.... buy a bag of Diamond or a bag of Imperial.. and blueboard a closet or basement office.. and have at it..

get a big plastic garbage can for mixing and a mud paddle.. , half inch drill...mix up a batch and start in..

if you can do durabond.. you can do plaster... i mean you might NOT want to do it for money.. but it's nice to know you can do it...

it's really cool for curves and compund curves...

(post #89057, reply #21 of 38)

Thanks Mike,

Sounds like a well thought out method , keeps the wire
back where it is protected and you end up with nice
deep boxes.

I must admit I'm a 2x6 fan , but if I was going to use
2x4 , I like your method to get up to that R19.

Always nice to read your posts, I like the way you think.


(post #89057, reply #22 of 38)

Yeah, one of these days I'll try it. I've done some patching, but never much volume. I'd like to try and make some architectural elements out of plaster, maybe learn how to do some details.

(post #89057, reply #23 of 38)

dawg..someone here turned me onto "Walls & Ceilings " online..

after i logged on.. they send me their mag every month...

try this..

(post #89057, reply #24 of 38)

dc, I always figure one stud per foot for 2x4's on 16" centers. This usually comes out pretty close and takes care of all your tees,corners, and cripples. In Arkansas where I live I think 2x4's are the way to go for outside walls.You can get up to an R-15 fiberglass insulation, but we usually use R-13.

(post #89057, reply #25 of 38)

Mike, I am still missing something here. You need to do an article for FHB on your technique (either that or patent it and sell the rights to use it and become rich...)

I assume your 3/4" furring is refering to something like a 1x2 (just what is the width?). Where does the foam board go? Do you cut it into strips and put it between the furring strips or do you put it behind the furring strips in the wall? How do you seal up the wall between the foam board and the furring strips or the studs? Or am I missing the picture completely (perhaps a photograph would help...)

(post #89057, reply #26 of 38)

The foam panels are applied directly to the studs...full coverage...from plate-to-plate and corner-to-corner. I don't know if Mike does this, but I gap the foam panels by about 3/8ths of an inch and foam the gaps and corners with canned foam. Gives a tight seal.

The furring strips are mounted horizontally on the face of the foam, with the fasterners going through the foam and into the studs.

When the drywall is screwed to the furring strips, you end up with a 3/4" air gap between the back of the drywall and the face of the foam. The drywall only touches the furring strips, not the foam.

For furring strips, mason's lathe is commonly's about 1" thick by 2" wide (3/4" by 1 1/2") and comes bundled in 8' lengths. My lumberyard has both "mason's lathe" and "furring strips". Sometimes they are interchangeable, sometimes the mason's lathe is thinner...maybe 5/8ths or 1/2" thick. The "furring strips" are always 1-by-2. Personally, I only use 1-by, or 3/4" thick, furring strips. Better holding power for drywall screws and other fastners. Where a wider piece of furring is desired I rip them to the desired width from 3/4" ply. It's a way to use up any 3/4" ply cutoffs leftover from the subflooring.

Though I'm only an hour away from Mike by car, I'm worlds away in terms of the availability of veneer coat plastering crews. They're still not too common around here, and when they are, the price is much higher.

(post #89057, reply #27 of 38)

Question for Mongo:

why use the furring strips at all? I was thinking that the drywall could be applied directly on top of the foam panels and screwed into the studs.

(post #89057, reply #28 of 38)


You can, and some do (apply drywall directly over foam).

Still, I prefer to have the "solid" backing of the wood furring behind the drywall. This is hard for me to describe, but I have screwed drywall through foam and into the studs (no furring), and occasionally the foam gets compressed and gets "sucked in," allowing the drywall to also "suck in". This can create a "depression" in the face of the drywall in the area around that screw. Someone who cares about the installation will note these deviations, back out the screws, and bring the face back into plane. But a typical rocking crew will simply slap the drywall up and start mudding. Once in a while, the force of the screw head holding the drywall and the foam in that compressed "sucked in" state is too much for the paper and gypsum to resist, and the drywall pops back out into plane on it's own. This results in the screwhead being torn through the face of the drywall and burying itself in the now fractured gypsum core.

What the furring strips do allow is fewer perforations through the foam and your vapor barrier/retarder when screwing the drywall. Drywall screws can be standard length (1 1/8th or 1 1/4") with furring vs having to use longer screws...2 1/2", for instance, to attach the drywall through the foam and into the studs. Also, depending on the crew, they may miss the studs more often when "blind shooting" longer screws through the thicker foam.

Though it's not normally a problem with walls, the furring strips can be shimmed to bring wall inconsistancies into plane. Shimming the furring strips is more common on ceilings when making up for the possible inconsistancies of 2-by stock used for joists/rafters.

Down the road, after the wall is up, it's easy to use a stud sensor to find the furring strips behind the drywall so you can use them for nailers.

I also find it easier to nail off window and door trim through the dryall and into the furring instead of nailing it off through drywall and foam, and finally into the studs.

As an added bonus, the dead air space between the foam and the drywall generally adds about another "1" to the R-value of the wall.

If using foil-faced RFBI, the furring strips give the foil an air space buffer to help it act as a radiant deflector.

Lastly, every drywall crew I know of is hesitant about screwing drywall directly over foam. Longer screws, blind screwing, throws their pace off. Some will refuse the job, others will often hit you with an upcharge for having to deal with the foam.

In the end, I don't think it's a "do or die" choice whether someone does or doesn't use furring strips over's just a minor preference on how I prefer to build walls.



(post #89057, reply #29 of 38)

that's about it ...

this was a series last year.. but i couldn't find it in the's a picture of the electric boxes with the 1.5 " plaster collar..

(post #89057, reply #30 of 38)

and a picture of the cathedral ceiling and sidewall , foamed and furred....

on the right side of the window you can see the foam plugs the insulators put in after they blew the cellulose into the walls...