With green framing all the rage I have been tempted to start using studs at 24-inch spacing rather than 16, as I’ve always done. How much will I really save doing this, and is it safe? I’m especially concerned with wavy drywall and siding.
Savings will come in several ways. First, you’ll use far fewer studs. Here’s an easy way to determine approximately how many you’ll save: number of studs saved=lineal feet of wall*0.25. As an example, say you’re building a 50-foot-by-50-foot, one-story house. The total length of exterior wall is 50*4=200 lineal feet. Let’s assume there are 100 lineal feet of interior wall. The total length of wall is therefore 200+100=300 lineal feet. If all of that is framed with studs at 24 inches rather than 16, the number of studs saved will be approximately 300*.25=75. That’s approximate because it doesn’t take into account doors and windows, but you could subtract out that lineal footage for more accuracy. If this were a two-story home, the number of studs saved would double: 75*2 floors=150.
The second form of savings is more indirect. All that wood left out creates additional space in walls for insulation. With our example home, at 1.5-inches in width multiplied by 75 each, that equates to 112-inches, or about 9.3 lineal feet of wall that will be filled with insulation rather than wood. This will, in time, translate to energy savings.
Here’s a third form of savings: labor. Fewer studs will mean less labor to haul, layout, and nail studs in place; less labor in nailing sheathing and drywall to studs; less mudding and sanding for drywallers; and less labor for electricians who route wire through holes they drill in studs. No single item here is a back breaker, but it all adds up.
Now for the downside. What about strength? Studs are the skeleton of any stick-framed house, so it stands to reason that removing a few bones might weaken the structure. That’s undoubtedly true. But the better question is, is what’s left still strong enough? A leg with two femurs would be stronger than a leg with one, but would it be better? Probably not. Let’s run some numbers.
In my neck of the woods, nearly all exterior studs are 2×6. What’s the capacity of a 10-foot long, 2×6 stud at 24-inch spacing? Where snow and wind loads are moderate—most of the U.S.—a No. 2 or better, Hem Fir, Spruce Pine Fir, or Doug Fir stud in the first story of a two-story house calcs with plenty to spare; it makes it by some 21%.
If a 10-foot-long stud calcs, a shorter one with the same parameters will too, and in fact will make it by a larger margin.