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Re: Cantilevers through a solid beam

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In a message dated 2/2/99 5:26:26 PM EST, 73527.1356(--nospam--at) writes:

<<  > I have a design problem where I need to build out the face of a patio
 . > the supporting beams by 16" - and add a parapet above this. The problem
 . > that the total depth of the beam and roof framing is limited to 16 inches
 . > - which happens to be the size of the Parallam required for a 24'-0" 
 . > span. The back-span of the rafters is less than 15 feet and the 
 . > cantilever is suppose to be, as I mentioned, 16 inches.
 . > 
 . > An idea came to me that I wanted to run by this group.
 . > 
 . > I need to extend at least a 2x4" member over the beam - which is not
 . > possible because of the restricted depth. Since this is the compression 
 . > side of the beam, I thought that I might be able to notch out the 2x4 in 
 . > the top side of the Parallam (3.5" depth) and extend the 2x4's through
 . > beam. When loaded, the beam will be in compression and the bottom of the
 . > rafter is above the neutral axis so that it remains in compression. I can
 . > strap this to compensate for a possible uplift by wind or seismic that 
 . > might place the upper side of the beam in tension.
 . > 
 . > Any thoughts on this?
 . > Any better suggestions?
 . > 
 . > Thanks,
 . > Dennis Wish PE
 . > 

You might try a piece of 1/4" bent plate, vertical leg about 6" and horiz. leg
about 4", notched over the top of the parallam.  The vertical leg is bolted to
the back span and the the cantilever.  You can notch the plywood around the
horizontal leg so you don't have to notch the parallam.  Provide a  3" wide,
1/4" steel stiffener plate each side of the parallam welded to the angle, this
will serve as a bearing plate for the vertical leg of the cantilever portion
of the angle as the cantilever portion trys to deflect forcing the vertical
leg against the side of the parallam.  You can also through bolt the stiffener
plates each side of the parallam to help with uplift.  At the end of the angle
you can put a saddle to bolt a facia beam or joist if you want, to align under
the parapet wall.  Space these bent plate every so often along the length of
the parallam as necessary, but probably not more than 8'-0" maximum.   Use 4x8
for the cantilever joist bolted to the bent plate.

Not the cheapest solution, but may not all that expensive.  We have used this
on an apartment walkway where there were occasional pop-outs and had a 3-6"
tall guard wall built on top of the end of the cantilever.  

poor picture:

             ____________________ bent plate notched over parallam w/ two
bolts each side of parallam
             |    parallam         |
            \|/   thru-bolt         \|/              ___ saddle at end of
-----------------------------|-------------------      /
        |   +       +   |_\|/__|    +    + |    /
        |__________|       |________|___
  backspan         parallam      16" cantilever

Good luck,

Michael Cochran