On Jun 29, 12:02*am, aemeijers wrote:
RicodJour wrote:
On Jun 28, 5:18 pm, "benick" wrote:
"Smitty Two" wrote in message
In article 4a47884e.691334325@localhost wrote:

In a free-standing garage, where one wall is almost entirely absent to
make
a door opening, what parts of the structure prevent the door wall from
racking?
The back wall.

You've NEVER seen a garage...LOL...Sorry about laughing but that was
funny...Once all 4 walls are up it will be fine...No extra thick sheathing
required..Use a 2X8 header with half inch sheating in the middle to make 3
1/2 inches for the wall thickness if using 2X4's.......

What does the header have to do with racking resistance? *A header
doesn't contribute to shear resistance. *Only connections and
construction that are designed to handle moments can resist the
racking.

Likewise one wall without the required shear strength will compromise
the entire building structurally. *You see shoddy construction all
over the place, and buildings that clearly don't have the structure to
handle the required present day shear loads, yet they are still
standing. *That doesn't mean that people should ignore the
requirements.

In the OP's case there is enough wall remaining in the door wall to
handle the shear. *The Simpson Strongwall is a more expensive
solution, but it works. *The diagonal bracing also works, but should
be let in to the studs as that increases its shear strength
considerably.

Sheathing either side of the door opening, inside and out, with glued
and nailed sheathing of at least 1/2" (nails not overdriven) would
probably be the easiest and strongest way to handle the shear load.
The specifics will depend on the local codes and design shear load.


If a header is strongly tied in to the wall corners, like with diagonal
bracing (or the gusseting of the corner sheathing), the whole wall can
be strong enough to resist racking. Almost like a bridge. If the header
is basically just sitting on the cripples at either end of the opening,
all it can do is catch weight from above. See my previous post about the
addition to my house down south- one continuous glue-lam header, from
original house wall, across added room, across carport bay, and all the
way across door wall of garage. Plywood sheathing on that end of garage.
Gone through 2 hurricanes so far- no twist, no sag, and overhead door
still operates with one hand.

Not that different from adding a 1x10 along the top back edge of cheap
pine shelving unit, to keep it from racking.

I was responding to Benick's post which is misleading. Headers are
also not usually built extending from corner to corner of a building
as you mention. They're cut to span the opening plus the length to
cover the supporting studs on either side. Of course you can modify
any construction to take shear loads, but just having a header doesn't
magically enable the wall-with-opening to resist moments. Your glulam
thing is not typical and not a basis for anything else other than your
house. You've had success with it, but it's not the way things are
usually built. I also don't know how your glulam was designed and the
details of the connection. It is still standing, so that definitely
means something, but I can't comment beyond that.

The shelving analogy has some merit, but it fails on the issue of the
magnitude of the forces. Wind design load can easily be +/- 15 PSF
simultaneously working on the walls and both sides of the roof. The
resultant force would be far greater than pretty much any typical
header connection would be able to withstand. This is why I said it
was misleading to imply that the typical header construction is
capable of satisfying the shear requirements. It can be done, but not
without knowing exactly what you are doing and the exact loads
involved.

Most shelving also has diagonal bracing and doesn't rely on resisting
a 6' moment arm (height of the shelving) with a 7"+ moment arm (the
1x10, fasteners 1" in from edges).

R