AskCodeMan

Hello Codeman,

Are you aware of an IRC code that would prohbit the following.

Typical platform framing.
First floor, exterior stud walls 2x4. Second floor, exteriror stud walls 2x6.

Thanks for your input.

Corey

Hi Corey,

Corey Friedman wrote:Are you aware of an IRC code that would prohbit the following.

The IRC does not prohibit that, thus it is 'allowed', but you would more likely see it as 2x4 studs in the exterior walls of both the first floor and the second floor if they were to use 2x4 studs.

Table R602.3(5) Size, Height and Spacing of Wood Studs allows for 2x4 studs, spaced 16 inches on center, to support one floor (the second floor) and the roof and ceiling above the second floor.

In fact, they could go 2x4 studs 16 inches on center for the first floor walls and 2x4 studs 24 inches on center for the second floor walls if they really wanted to.

However ... the problem with 2x4 studs comes in when one goes to insulate the exterior walls to the required R-value, which likely would require 2x6 stud space for the insulation for normal fiberglass insulation.

Now ... as to WHY ... someone would build with 2x4 studs for the first floor walls and 2x6 studs for the second floor walls is unknown to me, almost like they read the plan wrong and the bottom exterior walls should be 2x6 with the second floor exterior walls being 2x4 (still having the insulation R-value problem)?

I would be very curious as to any engineering which went into that structure as if 2x6 studs are 'needed' for the second floor walls, then most certainly 2x6 studs would be 'needed' for the first floor walls.

(Still waiting on hearing back from some others on your electrical question, if I don't hear anything back from them by tomorrow I will post my thoughts on it anyway.)