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

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Bill:


The idea of the rafters meeting at the ridge board is because they are
supposed to push on each other horizontally there.  If the rafters don't
butt at the ridge board then the ridge board is acting like a beam and might
be overloaded, the rafters might tweek the ridge board in weak axis bending
or a toenailed rafter-to-ridge board connection might fail. The only thing
that might save you is if the  roof sheathing is causing the whole deal to
act like a shell but this is unquantifiable.

I have never personally seen an local old house constructed improperly, but
I would expect there might be sagging with snow load.  I have driven by and
seen rafter roofs get droopy here but couldn't climb into the attics to see
what the deal was.

Also I am still truly sorry that Texas is so much smaller in comparison with
Alaska.  I would urge all readers to tell thier congressional delegation to
stop oil drilling in Texas since the fragile pristine Texan ecosystem is at
risk and to urge our president to declare Texas a National Monument.


Respectfully,

Scott M Haan P.E.
Plan Review Engineer
Building Safety Division 
Development Services Department
Municipality of Anchorage
http://www.muni.org/building
phone:907-343-8183  
fax:907-249-7399
mailto:haansm(--nospam--at)ci.anchorage.ak.us



-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
Sent: Friday, October 19, 2001 6:08 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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