Strength of 2×6″ – 24″ Center vs 2×6″ – 16″ center
I am about to start building a house and wanted to go with 2×6″ – 24″ spacing on the exterior walls and 3/4″ drywall. It has been widely discussed on the forums and in articles I have read as part of the “Advanced Framing”. Does the strength of the wall equal or compare closely to the 2×4″ 16″ center that has been used for decades with no issues? Or should I stick with 16″ centers with the 2×6 wall and sacrifice some R value to keep a “sturdy” wall?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Just follow the code and you'll be fine. 2x6 @ 24" is perfectly fine for a 2-story house.
To follow up on Nathan's comment, Table R602.3(5) in the 2018 IRC, or the equivalent table in your local code, will give you a starting point to figuring out what stud size and spacing is appropriate for your wall.
For me building a house is long stressful process it is very important to shop for a builder like you were shopping for a spouse. You need to feel you builder has your back. The last thing you want to do is start your relationship by pushing them to do something they are not comfortable with. You will almost certainly have disagreements big and small it is important that you can work thru them together.
If you are doing a layer of exterior foam I think the framing is less of a factor.
If you are the type that slams their doors stay with 16”.
3/4 inch drywall????
Just a caution not to confuse Advanced Framing with 2"x6"s at 24". Advanced Framing uses an number of techniques, like single top-plates, no jack studs, aligning load paths, etc. In contrast 2"x6' at 24" has been an accepted common conventional framing for decades.
To answer your question, 2x6 at 24" uses slightly more board-feet of wood and could support more vertical load. Its deeper section also will resist more wind load. An added benefit of 2x6 construction is the ability to fit larger headers and beams for large openings and the ability to fit plumbing and electrical. Disadvantages include losing floor space and the additional trim at penetrations.
How "sturdy" do you want it, and what sort of wind rating does it have to withstand?
One of the more relevant details is subfloor and floor joists, actually. You want walls to line up with floor joists and roof trusses. 24" OC removes the option of going with the cheapest thinnest floor sheathing (you get deflection between joists), and increases the deflection of the joists themselves, all other things being equal. Achieving a stiffer subfloor than code-minimum, and limiting exploding levels of absolute deflection in open-plan two-stories, is an active interest of many homebuilders. You can address this in cheaper ways, though, by simply making the floor joists deeper (shifting to engineered I-joists or open-web floor trusses).
I think 24" OC is well on its way to being the new standard. The campaign for this spacing is half a century old now.
Generally speaking, using a tight nailing schedule and fully sheathing exterior walls is going to give an enormous upgrade to wind rating, relative to century-old homes that were working with bracing or boards in place of sheet goods.
My builder friends on the Canadian prairies tell me they are almost exclusively on 24" oc. for everything now. They use open-web floor trusses with thick subfloor so the basement and main floor can be clear-spanned.
Here on the coast in seismic-land we are going the opposite way. The shear-walls typically get called out at 16" oc, so the rest of the walls and floor follows. Trusses are all that's left at 24".
Shouldn't the comparison really be to 2x4 at 16"?