[Greenbuilding] [Cob] Building failures-Snow Loads

[SANCO Business Group, LLC]

Ed wrote,

>Paul: When I took strength of materials in college there was a booklet put  
>out by the lumber industry that had tables giving lumber dimensions for various 
> roof and floor spans. Do you know if that booklet exists? Better yet do the  
>tables exist on line where they might be accessible to people  designing a 
>roof or floor?

Quentin Wilson offers the following,

Actually, the 2003 International Residential Code with the 2006 
edition coming out sometime soon, has floor joist and roof joist and 
rafter tables for various species of wood which are straightforward 
and easy to understand with 10- to 15-minutes of study. It is 
prescriptive and requires no calculations. (Old UBC's have these 
tables in even greater detail.)

For those interested in using wood I-Beams such as TJI's formerly 
from Mcmillan then Trus Joist of Weyerhaeuser now iLevel 
(www.iLevel.com [What the Pluperfect Hell is that guy doing with his 
pants?]), or Georgia Pacific's Wood I-Beam (www.gp.com) or Lousiana 
Pacific's LP I-Joists (www.lpcorp.com) or other major or minor 
players in the building material supply game, everything you need to 
know can be found on the Internet. In almost all cases, if someone is 
going to buy their proprietary system materials which usually 
includes the structural members, the sheathing or decking materials 
and the fasteners, adhesives and hangers, they do all the required 
engineering. The owner/builder/contractor/architect has only to 
choose the appropriate live load for the roof system which in light 
of Paul's remarks we might begin to think about 60psf even in mild 
mannered NM. For all these systems the Code simply says to follow the 
manufacturer's recommendations.

Then there is the viga and beam option. I have the viga span chart 
from the 1930's done by an engineer for William Lumpkins office 
passed on to me by Mark Chalom. I think it's on my webpage or maybe 
here in the yahoo archives. If not, I will post it soon. (Before the 
decade ends.) It is for roofs with lightweight insulation and 40 or 
60psf live loads. Joe Tibbets has a span chart for heavy weight roofs 
with dirt maybe 8- or 12-inches thick. It's in his Adobe 
Encyclopaedia. No longer in print it is available as a CD from him at 
www.somethingorotherbutIcantrememberatthemomentbutgoogleshoulddothetri
ckforyou.com

Once again the IRC 2003 and the old UBC 97 has the underlying 
formulas for calculating allowable beam spans. For those who don't 
have PhD's in math like me, you have but to wander the Internet a bit 
to find plug-in formulas. Or try the library for a Timber 
Construction Handbook. 

SANCO Business Group
Paul Salas, Gen Mgr
PO Box 45741
Rio Rancho, NM  87174
(505)  238-0426
paul at sanco-bg.com
visit us http://www.sanco-bg.com