Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Conventional Lumber Diaphragms

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Good question on part 1. I would be interested in the reason for that too.
In regard to part 2 I believe it has to do with the required fire rating of
the roof. Most jurisdictions in California require minimum class C rating on
roof assemblies. If I am not mistaken, to obtain class C rating you need
solid sheathing below the roof tile or shake.

	-----Original Message-----
	From:	NRoselund(--nospam--at)aol.com [SMTP:NRoselund(--nospam--at)aol.com]
	Sent:	Thursday, September 16, 1999 5:47 PM
	To:	seaint(--nospam--at)seaint.org
	Subject:	Conventional Lumber Diaphragms


	I have a project for an addition to an old house and garage.  New 
	construction is to match the old, or old style to the extent
possible.

	1.  Sections 2315.3.1 and 2315.2 of the '97 UBC give instructions
for 
	construction of diaphragms of diagonal 1x lumber.  Table 23-II-G
specifies 
	span-width ratios for diagonal-board-sheathed horizontal and
vertical 
	diaphragms.  I can't find allowable values.  Am I overlooking a
Table or 
	Section of the Code?  

	Appendix Chapter 1 on the UCBC has allowable values for horizontal
diaphragms 
	of wood diagonal sheathing with either roofing or hardwood flooring 
	coverings, but this is a code for existing construction, not new,
and does 
	not include values for shear walls.

	2.  Section 2320.12.9, Roof Sheathing, allows spaced roof sheathing
for 
	conventional construction.  Chapter 15 allows spaced board sheathing
under 
	tile and wood shingle roofs.  Why does re-roofing universally
include plywood 
	sheathing over existing spaced sheathing?  (At least in S.CA it
does.)

	Nels Roselund
	Structural Engineer