2×4 vs. 2×6 Exterior Framing
I’m planning my new home in Colorado (climate 5b). We have a very limited building envelope, and so wall thickness is of concern – complicated by the fact that my wife is set on using brick veneer.
That said, I’m going back and forth with using 2×4 framing vs. 2×6 and would love any input on disadvantages of the narrower wall. Doesn’t seem like a lot, but the additional few inches does help.
– Achieving the IRC Table 402.1.1 insulation requirements (R-13 cavity + R-5 exterior) doesn’t seem to be an issue with the 4″ wall. Assembly will most likely be spray foam cavity, 1-1/5″ rigid exterior, 1″ air gap, then brick veneer.
– Plates are 9′, so I realize there may be some concern with the straightness of a 4″ stud.
– The structure is such that none of mu columns need be deeper than 3-1/2″.
Thanks for any help!
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Replies
Brad,
Two issues here: structural and thermal.
If you are unsure of the structural issues, talk to an engineer. Briefly, most single-story buildings can have 2x4 walls, while many two-story buildings require 2x6 walls -- but there are all kinds of exceptions. You can't design the walls until you know the loads.
The thermal issues are complicated, too. Most people here at GBA will suggest that if you want more insulation, it's better to install the thicker insulation as a continuous layer of insulation on the exterior side of your wall sheathing. (That usually means rigid foam or mineral wool.) Thicker exterior insulation makes more sense than thicker studs filled with fiberglass batts.
-- Martin Holladay
I've read that for brick a 2" gap is recommended.
Deeper studs can require thicker exterior foam in order to keep the sheathing warm enough to prevent condensation.
If it's permitted by code and structurally sound from a cost comparison perspective you'd want to compare 2x6 on 24" centers vs 2x4 on 16" centers.