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RE: RESIDENTIAL: Rafters Not Meeting At Ridge Plate -- Staggered Spacing

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If by "lateral load resisting element" you mean the capacity of the roof as a diaphragm, I don't think the offset spacing of the rafters would impact the shear capacity of the plywood sheathing.

-----Original Message-----
From: Bill Polhemus [
mailto:bill(--nospam--at)polhemus.cc]
Sent: Friday, October 19, 2001 10:08 AM
To: seaint(--nospam--at)seaint.org
Subject: RESIDENTIAL: Rafters Not Meeting At Ridge Plate -- Staggered
Spacing


I am doing a forensic investigation for a "tract home" built by a well-known
homebuilder in the Houston area. One of the more surprising things I found
was that the rafters do not meet (are not collinear) at the ridge plate but
rather are staggered along the length of the plate. The spacing isn't even
regular, but random.

According to UBC '97 2320.12.3 "Rafters shall be framed directly opposite
each other at the ridge." Obviously we see a code violation here, but I'm
interested in the implications of this. My assumption is that even though
the ridge plate might be able to withstand the lateral thrust of the rafter,
the roof is considerably less stiff as a lateral load resisting element,
which could have some problems.

Can someone make any other observations about potential problems?

Also, secondarily the contractor apparently "forgot" to install a ridge vent
in the roof. There are only two turbine vents in the entire roof (this for a
house with approx. 1,500 sq. ft. of footprint area). Since I'm seeing a
"rippling effect" in some of the roof decking, I'm assuming that there's
"bad stuff" happening with excess heat in the attic space.

What are the implications of improper venting of the attic space? Any
thoughts on this?


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