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RE: Roof Blocking

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Chris, there are a few ways to do this. You can overlap the block and use a
Simpson A35 on the backside to the block and double plate. You could also
use 4x blocking, but this can get expensive.
The final way is to install the full depth shear blocking as the code
requires - above the double plate and then lay in the stucco molding with
2x4's (same as frieze block)flat on the outside face of wall and in line
with the soffit framing.
Although not commonly done, you can use a 2x blocking laid flat for the
stucco and place another 2x above it connecting the roof to the flat block.
Just make sure that each is properly nailed to get the shear transfer.
One final way will work if the roof is stacked lumber (rather than plated
trusses). If you have long rafter tails and a dropped soffit (below the top
plate of the wall), you can ledger the soffit or eave framing which creates
a stucco connection at the bottom of the ledger.

Production builders in my are going for the 2x full depth blocking eccentric
to the wall and installing A35's to each block on the plate side to make the
shear transfer.

Whatever you do, make sure you boundary nail the diaphragm to the blocking.

Dennis S. Wish PE

-----Original Message-----
From: Serroels, Chris/SAC [mailto:CSerroel(--nospam--at)CH2M.com]
Sent: Wednesday, December 16, 1998 4:31 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: Roof Blocking


Question regarding roof blocking to the top plate:

The framing for my own home is currently underway.  This happens to be my
first venture into the timber construction arena.  When it came time to
block between the rafters and the top plate, the framer saw my plans and got
a strange look on his face.  He asked how in the world I intended to attach
the blocking to the top plate.  I got a strange look on my face and asked
why in the world that is a problem.  He then proceeded to show me "how it is
always done".  He said that the block is held about an inch (horizontally)
out from the top plate then nailed to the rafter tail.  The inch clearance
is so that the stucco installers can place the foam (one coat stucco system)
behind the blocking.  I asked why the blocking wasn't placed on top of the
top plate and shaped to match the sheathing.  He said that if I did this,
then the stucco people would have to plaster between the rafter tails (added
cost).  I believe the term used to describe this was "frieze" blocking or
frieze board.

Problem is, with the blocking held out from the top plate it doesn't provide
shear transfer between the sheathing and plate.  What I am having them do is
double block.  One row of blocking held out from the top plate to serve as
the frieze blocking and one row of shaped blocking on top of the plate to
provide the shear transfer.

Question is - is this unconventional (the double blocking).  If so, how is
it done elsewhere?

Chris Serroels
CH2M HILL/Sacramento
cserroel(--nospam--at)ch2m.com