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2x4 exterior walls on new construction

jar546

jar546

CBO
Joined
Oct 16, 2009
Messages
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Location
Not where I really want to be
Educational:

A builder wants to construct a 2 story house utilizing 2x4 exterior wall construction @ 16" O.C. The home will be 34' wide by 50' long and have a gable roof running lengthwise.

Is this allowable?

You have everything you need to answer this question. Energy codes, ground snow load, etc. are not relevant.
 
mark handler said:
Which code edition?
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It's slipped into the 2009 IRC as a footnote in Table R602.3(5); "c. A habitable attic assembly supported by 2 X 4 studs is limited to a roof span of 32 feet. Where the roof span exceeds 30 feet, the wall studs shall be increased to 2 X 6 or the studs shall be designed in accordance with accepted engineering practice."

This is a prime example of the code running amuck. I'll bet this was just slipped in and not voted on. Here is why:

1. It refers to "only" a habitable attic assembly's support and not the exterior walls Jeff refers to in the OP.

2. So, yes you can use 2 X 4 studs for the exterior walls, even if you have a habitable attic; as long as the walls do not support part of the habitable attic assembly.



3. How do you "design 2 X 4 walls in accordance with accepted engineering practices? Oh, I forgot; by putting an engineer's seal on the plans. :)

4. I suspect JP of sneaking that in. j/k

ps. Jeff said nothing about a habitable assembly.

"A builder wants to construct a 2 story house utilizing 2x4 exterior wall construction @ 16" O.C. The home will be 34' wide by 50' long and have a gable roof running lengthwise."

I wish they would quit playing silly games with the codes.

Uncle Bob
 
Last edited by a moderator:
See it all the time. Well, used to anyway. Not too much going on in the way of new home construction in my neck of the woods right now.
 
ps. Jeff said nothing about a habitable assembly."A builder wants to construct a 2 story house utilizing 2x4 exterior wall construction @ 16" O.C. The home will be 34' wide by 50' long and have a gable roof running lengthwise."
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You are correct I just threw in the habitable attic because it is still just a 2 story house under the code and an example of needing all the info before giving a blanket answer to a general question.
 
No. The house is on a sloped site, and the basement is a garden level in the back. It does not qualify as a story above grade. The half walls completing the rear wall of the basement are "exterior walls" of a "two story home" and they cannot be 2x4 at 16 inch on center, because they carry two floors and a roof.
 
jar546 said:
The home will be 34' wide by 50' long and have a gable roof running lengthwise.
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Please explain "running lengthwise". Do you mean the gable triangle is on the 50' side or the 34' side?

If the 50' side, then the answer is definitely NO.
 
No, there is a one car garage planned for the ground level with a second story above. The garage is to open on the 50 ft. face. The largest span for a prescriptive header that will fit in a 2x4 wall over the 8 ft door and supporting one floor with center bearing and a roof under the lowest snow load and the 36' building width is 6' 5". That's a double 2x12. To get an 8' 3" header to accommodate jams you will need a three ply header. A three ply header cannot be supported in a 2x4 wall. I presume this game is for prescriptive code means only? No engineering allowed to play?

I suppose this is the game? Find conditions where the blanket question asked could indeed have a "no" answer?
 
No. They are using braced wall methods LIB and GB in a wind region between 100 and 110 mph, and there are no interior braced walls. The braced wall interval is 50 feet and thus 44 ft of braced wall panels are required, but only 30 are available. They can't even do it with 2x6 walls unless they choose a different braced wall method...

This is just one example. Braced wall type, height of studs, wind speed seismic category, and size and location of openings can all affect the construction of a 2 story 30 x 50 prescriptive home...leading to an answer of "no".
 
jar546 said:
Educational:A builder wants to construct a 2 story house utilizing 2x4 exterior wall construction @ 16" O.C. The home will be 34' wide by 50' long and have a gable roof running lengthwise.

Is this allowable?

You have everything you need to answer this question. Energy codes, ground snow load, etc. are not relevant.
Click to expand...
Do the walls exceed 10' 4 1/2" high? I think that's the limit for 2x4 construction.

Brent.
 
Glenn said:
No, there is a one car garage planned for the ground level with a second story above. The garage is to open on the 50 ft. face. The largest span for a prescriptive header that will fit in a 2x4 wall over the 8 ft door and supporting one floor with center bearing and a roof under the lowest snow load and the 36' building width is 6' 5". That's a double 2x12. To get an 8' 3" header to accommodate jams you will need a three ply header. A three ply header cannot be supported in a 2x4 wall. I presume this game is for prescriptive code means only? No engineering allowed to play?I suppose this is the game? Find conditions where the blanket question asked could indeed have a "no" answer?
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There are several engineered lumber solutions to solve that, as well as steel. I could even put the header at floor level on the second story and frame down to get compliant.

Brent.
 
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