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Posted by Bob Morrison on October 20, 2006, 10:30 am
In a previous post Ken S. Tucker wrote...
show/hide quoted text
> Well if it's 5/8" tongue & groove, which is
> easy to glue and a bit of easy pounding,
> usually makes a good fit. Not sure any
> tangible benefit can be derived for the labor
> of blocking.
>
Ken:
Actually, there is a structural benefit. A blocked diaphragm has a higher
load capacity for the same nail spacing as an unblocked diaphragm.
Having said that, it takes a pretty big roof (think 60x100) before one
even begins to approach the load capacity of an unblocked diaphragm.
For 7/16" OSB or 15/32" plywood, edge clips at midspan are required by
code when the support spacing is more than 16" o/c. However, if you use
19/32" (5/8") sheathing then clips are not required.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
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Posted by Ken S. Tucker on October 20, 2006, 2:15 pm
Bob Morrison wrote:
show/hide quoted text
> In a previous post Ken S. Tucker wrote...
> > Well if it's 5/8" tongue & groove, which is
> > easy to glue and a bit of easy pounding,
> > usually makes a good fit. Not sure any
> > tangible benefit can be derived for the labor
> > of blocking.
> Ken:
> Actually, there is a structural benefit. A blocked diaphragm has a higher
> load capacity for the same nail spacing as an unblocked diaphragm.
I've used blocking between trusses to keep
them aligned vertically, but because the roof
was T&G, I didn't worry about them being
carefully aligned to any seam so the blocks
could be offset for easy nailing. A floor is
a different story (pun) because a live load
moves on it and blocking transfers load to
adjacents joists. But a roof has a dead snow
load, and for the most part, each truss is
equally burdened so blocking them for
strength is not very effective, that I can see.
show/hide quoted text
> Having said that, it takes a pretty big roof (think 60x100) before one
> even begins to approach the load capacity of an unblocked diaphragm.
> For 7/16" OSB or 15/32" plywood, edge clips at midspan are required by
> code when the support spacing is more than 16" o/c. However, if you use
> 19/32" (5/8") sheathing then clips are not required.
Not sure I recall Don mentioning his roof
sheathing, certainly if it's not T&G then
blocking for the edges is certainly best,
(I've done that on small buildings).
show/hide quoted text
> --
> Bob Morrison, PE, SE
> R L Morrison Engineering Co
> Structural & Civil Engineering
> Poulsbo WA
> bob at rlmorrisonengr dot com
Thanks
Ken
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Posted by Bob Morrison on October 20, 2006, 7:40 pm
In a previous post Ken S. Tucker wrote...
show/hide quoted text
> I've used blocking between trusses to keep
> them aligned vertically, but because the roof
> was T&G, I didn't worry about them being
> carefully aligned to any seam so the blocks
> could be offset for easy nailing. A floor is
> a different story (pun) because a live load
> moves on it and blocking transfers load to
> adjacents joists. But a roof has a dead snow
> load, and for the most part, each truss is
> equally burdened so blocking them for
> strength is not very effective, that I can see.
>
Ken:
I should have been more specific. The higher load capacity is for LATERAL
LOADS, not gravity loads like snow.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
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Posted by Ken S. Tucker on October 21, 2006, 12:58 pm
Bob Morrison wrote:
show/hide quoted text
> In a previous post Ken S. Tucker wrote...
> > I've used blocking between trusses to keep
> > them aligned vertically, but because the roof
> > was T&G, I didn't worry about them being
> > carefully aligned to any seam so the blocks
> > could be offset for easy nailing. A floor is
> > a different story (pun) because a live load
> > moves on it and blocking transfers load to
> > adjacents joists. But a roof has a dead snow
> > load, and for the most part, each truss is
> > equally burdened so blocking them for
> > strength is not very effective, that I can see.
> Ken:
> I should have been more specific. The higher load capacity is for LATERAL
> LOADS, not gravity loads like snow.
Hear ya, wow, as a kid I loved studying the
inside of old barns, could almost smell the
sweat and intelligence in framing those roofs.
The timber in those is awesome, especially
the axe marks.
In the progressive 60's and 70's those were
discarded as junk as New & Improved metal
tech vogued, and the original barns were left
to decay. But you gotta love the neat truss
designs they used, and as you mention,
designed for serious lateral (wind+) loads too.
Recall the different styles of lightning rods?
Thanks
Ken
Ps: a helicopter just landed in the neighbours
yard.
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Posted by Ken S. Tucker on October 21, 2006, 2:12 pm
Ken S. Tucker wrote:
show/hide quoted text
> Ps: a helicopter just landed in the neighbours yard.
Turns out they we're just practising, but the neighbours
aren't there - it's an empty lot - so wife asked them about
it. Fortunately alls well and good.
Ken
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> easy to glue and a bit of easy pounding,
> usually makes a good fit. Not sure any
> tangible benefit can be derived for the labor
> of blocking.
>