| Author |
roof thrust problem
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| jbusboom@gmail.com 2006-08-22, 5:25 pm |
| I am building a 20 foot wide barn with a gambrel roof. The trusses are
specially engineered so that no chords are needed (almost like a
scissor truss). This allows me to use the top of the barn as a loft.
But, I want to raise the height of the walls on which the trusses are
supported by 18 to 24 inches so that I have extra head room on the loft
level of the barn. Normally, the floor joists would stop the wall
spreading caused by the thrust of the roof, but since I am raising the
wall height, that is not the case anymore. Will I have a problem if I
don't add any more supports elsewhere (I am not about to use flying
buttresses on my barn). One potential solution I have is to use some
cross bracing from the top of the wall down inward to the floor joists
at an angle every so often along the wall, like:
/
/
/
|\
| \
|----\---------
|
That way I get the extra head room, and the braces won't be in the way.
Any thoughts?
| |
|
| Personally I would do it just like your little illustration. I
would nail the brace onto the rafter itself and down to the
joist.. Only 20' wide is not much more than a small shed and the
loads have to be small. I'm sure someone will come up with a more
complicated way though.
<jbusboom@gmail.com> wrote in message
news:1156281303.746655.311310@75g2000cwc.googlegroups.com
>I am building a 20 foot wide barn with a gambrel roof.
> The trusses are specially engineered so that no chords
> are needed (almost like a scissor truss). This allows me
> to use the top of the barn as a loft. But, I want to
> raise the height of the walls on which the trusses are
> supported by 18 to 24 inches so that I have extra head
> room on the loft level of the barn. Normally, the floor
> joists would stop the wall spreading caused by the thrust
> of the roof, but since I am raising the wall height, that
> is not the case anymore. Will I have a problem if I
> don't add any more supports elsewhere (I am not about to
> use flying buttresses on my barn). One potential
> solution I have is to use some cross bracing from the top
> of the wall down inward to the floor joists at an angle
> every so often along the wall, like:
>
> /
> /
> /
> |\
> | \
> |----\---------
> |
>
> That way I get the extra head room, and the braces won't
> be in the way. Any thoughts?
| |
| bitternut 2006-08-22, 8:25 pm |
| We had a large two story barn that was constructed exactly as your
illustration. It was built about 1900 and is still standing very nicely. We
used to load up the second story with a lot of stuff that seemed to do no
harm.
"Glenn" <pilcheg@kc.rr.com> wrote in message
news:fvLGg.63695$zg.32151@tornado.rdc-kc.rr.com...
> Personally I would do it just like your little illustration. I would nail
> the brace onto the rafter itself and down to the joist.. Only 20' wide is
> not much more than a small shed and the loads have to be small. I'm sure
> someone will come up with a more complicated way though.
>
> <jbusboom@gmail.com> wrote in message
> news:1156281303.746655.311310@75g2000cwc.googlegroups.com
>
| |
| jbusboom@gmail.com 2006-08-23, 9:25 am |
| I am encouraged that a barn build this way over a hundred years ago is
still standing. Do you remember how often along the wall that the
braces were placed? Was it from every rafter (or truss) or more
separated. I would think doing it from every rafter would be a bit
overkill.
bitternut wrote:[color=darkred]
> We had a large two story barn that was constructed exactly as your
> illustration. It was built about 1900 and is still standing very nicely. We
> used to load up the second story with a lot of stuff that seemed to do no
> harm.
> "Glenn" <pilcheg@kc.rr.com> wrote in message
> news:fvLGg.63695$zg.32151@tornado.rdc-kc.rr.com...
| |
| Darryl Bailie 2006-08-23, 1:25 pm |
| When we specify raised tie trusses we specify that they sit on glide shoes.
These let the trusses spread without inducing lateral loads on the top of
the wall.
<jbusboom@gmail.com> wrote in message
news:1156281303.746655.311310@75g2000cwc.googlegroups.com...
>I am building a 20 foot wide barn with a gambrel roof. The trusses are
> specially engineered so that no chords are needed (almost like a
> scissor truss). This allows me to use the top of the barn as a loft.
> But, I want to raise the height of the walls on which the trusses are
> supported by 18 to 24 inches so that I have extra head room on the loft
> level of the barn. Normally, the floor joists would stop the wall
> spreading caused by the thrust of the roof, but since I am raising the
> wall height, that is not the case anymore. Will I have a problem if I
> don't add any more supports elsewhere (I am not about to use flying
> buttresses on my barn). One potential solution I have is to use some
> cross bracing from the top of the wall down inward to the floor joists
> at an angle every so often along the wall, like:
>
> /
> /
> /
> |\
> | \
> |----\---------
> |
>
> That way I get the extra head room, and the braces won't be in the way.
> Any thoughts?
>
| |
| jbusboom@gmail.com 2006-08-23, 5:25 pm |
| I don't know what glide shoes are and couldn't find a good explanation
on the net...the trusses I am using are made onsite and use plywood
gussets at all of the intersections. A picture can be found here:
http://www.barnplans.com/trusses.html
It's the top picture, although you can't see the truss very well at
that angle. Other pictures on the site show a better picture.
Darryl Bailie wrote:[color=darkred]
> When we specify raised tie trusses we specify that they sit on glide shoes.
> These let the trusses spread without inducing lateral loads on the top of
> the wall.
>
>
> <jbusboom@gmail.com> wrote in message
> news:1156281303.746655.311310@75g2000cwc.googlegroups.com...
| |
| Bob Morrison 2006-08-23, 5:25 pm |
| In a previous post jbusboom@gmail.com wrote...
> I am building a 20 foot wide barn with a gambrel roof. The trusses are
> specially engineered so that no chords are needed (almost like a
> scissor truss). This allows me to use the top of the barn as a loft.
> But, I want to raise the height of the walls on which the trusses are
> supported by 18 to 24 inches so that I have extra head room on the loft
> level of the barn. Normally, the floor joists would stop the wall
> spreading caused by the thrust of the roof, but since I am raising the
> wall height, that is not the case anymore. Will I have a problem if I
> don't add any more supports elsewhere (I am not about to use flying
> buttresses on my barn). One potential solution I have is to use some
> cross bracing from the top of the wall down inward to the floor joists
> at an angle every so often along the wall, like:
>
One option is to balloon frame the walls to the truss support point.
If the walls are already in place then I suggest you contact a local
engineer for a solution. The building inspector, if he is alert, will
most likely require an engineered solution anyway.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
| |
| Kickstart 2006-08-23, 5:25 pm |
| I am using are made onsite and use plywood
> gussets at all of the intersections. A picture can be found here:
>
> http://www.barnplans.com/trusses.html
>
> It's the top picture, although you can't see the truss very well at
> that angle. Other pictures on the site show a better picture.
your link answers your question
"Engineered trusses are designed to transfer any lateral forces directly
downward onto the side walls. This eliminates the need for upstairs post
and beam supports"
kickstart
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| Darryl Bailie 2006-08-25, 9:25 am |
| You must be able to get something like this in the States
http://www.alpeng.co.uk/publication...russ%20clips%22
Darryl
<jbusboom@gmail.com> wrote in message
news:1156366535.626993.199580@m73g2000cwd.googlegroups.com...
>I don't know what glide shoes are and couldn't find a good explanation
> on the net...the trusses I am using are made onsite and use plywood
> gussets at all of the intersections. A picture can be found here:
>
> http://www.barnplans.com/trusses.html
>
> It's the top picture, although you can't see the truss very well at
> that angle. Other pictures on the site show a better picture.
>
>
> Darryl Bailie wrote:
>
| |
| RicodJour 2006-08-25, 1:25 pm |
| Darryl Bailie wrote:
> When we specify raised tie trusses we specify that they sit on glide shoes.
> These let the trusses spread without inducing lateral loads on the top of
> the wall.
The knee walls have to be able to carry the lateral loads from seismic
and wind loading. It's not just a question of the truss and truss
connections. Balloon framing is probably the easiest way to go.
R
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