[Greenbuilding] Advanced framing/OVE / 100 years from now

[John Salmen]

Virtually equivalent meant 'serves the purpose' compressive loading @ 24" 
o.c.. works.

lateral stability with wall sheathed for spf 'stud' grade (which I would
assume all lumber to be even if marked #2) is 675 psi so the numbers are
much higher for loading than your giving. We are talking about interior wall
loading here not exterior subject to wind loading. Wind loading can reduce
allowances to much less than 2800 lbs., so that deserves different
attention.

The basic point here is that a 2x4 will hold a house up and CAN be used in
multistory construction with the proper design considerations. The
additional point is that people should use proper design considerations but
if anything I think should 'err' on the side of conservation rather than the
typical north American excess. 2x6 construction is an energy hog. 


JOHN SALMEN ENVIRONMENTAL DESIGN
4465 UPHILL RD,. DUNCAN, B.C.  CANADA, V9L 6M7
PH 250 748 7672 FAX 250 748 7612 CELL 250 246 8541
terrain at shaw.ca


-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Rob Tom
Sent: March 8, 2007 10:48 AM
To: GB REPP
Subject: Re: [Greenbuilding] Advanced framing/OVE / 100 years from now

On Wed, 07 Mar 2007 12:48:00 -0500, John Salmen <terrain at shaw.ca> wrote:

> If a 2x4 represents 1/3 less lumber than a 2x6 and is virtually  
> equivalent in load bearing

> Lawrence Lile wrote:

>> 2X4 on 24" centers isn't very good construction, IMHO.

FWIW, for stud-grade SPF dimension lumber "2-bys" 2400mm long (~8 ft),  
laterally-supported (ie by sheathing), using LSD (no Alan, not LSD a la  
"Wavey Gravy",  LSD = Limit States Design) procedure for compression  
members, (ie Pr = phi*Fc*A*Kd*Ksc*Kt*Kh*Kc) and a quickie back-of-the  
envelope calc, then the axial load capacity of:

   a 2x4  = 12.7 KN (~ 2850 lbs)
   a 2x6  = 22.8 KN ( ~5116 lbs)

Which is to say that literally-speaking, a 2x4 stud is not equivalent to a  
2x6 stud in loadbearing, obviously.

For a single storey 9m (30 ft) wide building where the stud is just  
supporting the live and dead loads of a simple trussed roof in a locale  
where there is snow loading, say 4.4 KPa combined factored LL + DL, the  
factored axial load on each stud would be 12.2 KN which is to say that 2x4  
studs @24" o/c would be fine .

Make that a 2 storey building so that the lower storey studs are carrying  
the loads from the second storey floor as well as the roof and the  
factored load on each stud goes up to 17.2 KN, beyond the capacity of a  
2x4 for this example scenario.

The key to OVE I suppose is the "Engineering" part.
What may seem like cheap insubstantial work may in fact be an elegant,  
efficient use of minimal materials if engineered properly. Improperly, and  
you may create bad situations.


=== * ===
Rob Tom
Kanata, Ontario, Canada
<A r c h i L o g i c   at  c h a f f y a h o o   dot   c a >
winnow the chaff from my edress in your reply


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