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?

I am second-guessing myself about my shed plan.  One wall, a gable end wall,
is non-load-bearing but is a shear wall.  Its plan has an 8x8 door opening
in a 12' wide by 9' high wall.  I don't have the background to determine
whether such a wall will have sufficient shear strength.  I'm using
conventional 2x4 framing 16" OC with APA-rated 7/16 OSB sheathing, no
interior sheathing is planned.

The obvious things would be to reduce the door opening, to use heavier
sheathing, and/or sheathe it inside and out.  But first I would like to hear
any advice this august group has to offer, and with my thanks.

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u...@asgard.slcc.edu 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?
> 
> I am second-guessing myself about my shed plan.  One wall, a gable end wall,
> is non-load-bearing but is a shear wall.  Its plan has an 8x8 door opening
> in a 12' wide by 9' high wall.  I don't have the background to determine
> whether such a wall will have sufficient shear strength.  I'm using
> conventional 2x4 framing 16" OC with APA-rated 7/16 OSB sheathing, no
> interior sheathing is planned.
> 
> The obvious things would be to reduce the door opening, to use heavier
> sheathing, and/or sheathe it inside and out.  But first I would like to hear
> any advice this august group has to offer, and with my thanks.
> 

Traditional way, in addition to stiff sheathing, was to cut in angle 
braces on all the corners. Try to create as many triangular sections at 
right angles to each other as you can. A large header, corner post to 
corner post, helps as well. On the addition to my house down south, we 
actually used about 35 feet of glue-lam all the way from the original 
house, over the open carport bay, and tied into the far corner of the 
new garage beyond. It has worked out real well- no movement in 2 
hurricanes since then. Carports in Louisiana hate hurricanes almost as 
much as mobile home in Arkansas  hate tornadoes.

I'd bump up the walls to 2x6 (so you can hang shelves on the walls), use 
thicker sheathing (real plywood beats OSB), consider using adhesive and 
nails on the sheathing, and use all recommended tie straps for your 
area. Truss or stick-frame roof? If you aren't finishing the inside at 
all, you can face-apply the triangular braces mentioned above on the 
inside, including tying the adjacent walls together at the level of the 
ceiling joists. That will make for very stiff corners.

Standard disclaimer- I'm not an engineer, but that is how I saw it done 
as a wee lad, and how I would do it.

--
aem sends...

In article <4...@localhost>,
 u...@asgard.slcc.edu 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.

On Sun, 28 Jun 2009 15:25:36 GMT,
u...@asgard.slcc.edu 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?
>
>I am second-guessing myself about my shed plan.  One wall, a gable end wall,
>is non-load-bearing but is a shear wall.  Its plan has an 8x8 door opening
>in a 12' wide by 9' high wall.  I don't have the background to determine
>whether such a wall will have sufficient shear strength.  I'm using
>conventional 2x4 framing 16" OC with APA-rated 7/16 OSB sheathing, no
>interior sheathing is planned.
>
>The obvious things would be to reduce the door opening, to use heavier
>sheathing, and/or sheathe it inside and out.  But first I would like to hear
>any advice this august group has to offer, and with my thanks.

You don't say whether or not you're in earthquake country....

If not, standard let-in diagonal bracing combined with properly
applied and nailed sheathing should be fine. 

If you are in earthquake or high-wind zone, or just want a beefier
design, Simpson makes pre-engineered shear walls designed for the
narrow walls next to garage door openings:

http://www.strongtie.com/products/strongwall/

Googling "shear wall design" will get you lots of info.

HTH,

Paul F.

"Smitty Two" <p...@earthlink.net> wrote in message 
news:p...@newsfarm.iad.highwinds-media.com...
> In article <4...@localhost>,
> u...@asgard.slcc.edu 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....... 

On Sun, 28 Jun 2009 17:18:21 -0400, in alt.home.repair, "benick"
<b...@fairpoint.net> wrote:

>
>"Smitty Two" <p...@earthlink.net> wrote in message 
>news:p...@newsfarm.iad.highwinds-media.com...
>> In article <4...@localhost>,
>> u...@asgard.slcc.edu 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...

Yeah, but it did make me stop and think.  I think he's partly right.  My
thinking did not take into account the roof structure and how it rigidly
ties all of the walls together.  It's certainly not the first "duh!" moment
I've had on this project, almost certainly not the last.

Thanks to all who have replied so far, you're giving me plenty to think
about.

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Due to Usenet spam, emailed replies must pass an intelligence test: if
you want me to read your reply, be sure to include this line of text in
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u...@asgard.slcc.edu wrote:
> On Sun, 28 Jun 2009 17:18:21 -0400, in alt.home.repair, "benick"
> <b...@fairpoint.net> wrote:
> 
>> "Smitty Two" <p...@earthlink.net> wrote in message 
>> news:p...@newsfarm.iad.highwinds-media.com...
>>> In article <4...@localhost>,
>>> u...@asgard.slcc.edu 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...
> 
> Yeah, but it did make me stop and think.  I think he's partly right.  My
> thinking did not take into account the roof structure and how it rigidly
> ties all of the walls together.  It's certainly not the first "duh!" moment
> I've had on this project, almost certainly not the last.
> 
> Thanks to all who have replied so far, you're giving me plenty to think
> about.
> 

yes typically the roof is pitched to the sides of the garage, not front 
and back - even if the garage is roughly square.  You don't want to have 
to walk through the wall o' water(tm) running off the garage roof to 
open the door, do you?  so if you have a garage design where there 
really is limited area for sheathing to provide support around the 
garage door you could add some bracing on the inside between the wall 
framing and the last roof truss

nate

-- 
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On Jun 28, 5:18=A0pm, "benick"  wrote:
> "Smitty Two"  wrote in message
> > In article <4...@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 sheathin=
g
> 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.

R

On Jun 28, 5:38=A0pm, u...@asgard.slcc.edu wrote:
> On Sun, 28 Jun 2009 17:18:21 -0400, in alt.home.repair, "benick"
>
>
>
>
>
>  wrote:
>
> >"Smitty Two"  wrote in message
> >news:p...@newsfarm.iad.highwinds-media.com..=
.
> >> In article <4...@localhost>,
> >> u...@asgard.slcc.edu wrote:
>
> >>> In a free-standing garage, where one wall is almost entirely absent t=
o
> >>> make
> >>> a door opening, what parts of the structure prevent the door wall fro=
m
> >>> racking?
>
> >> The back wall.
>
> >You've NEVER seen a garage...LOL...Sorry about laughing but that was
> >funny...
>
> Yeah, but it did make me stop and think. =A0I think he's partly right. =
=A0My
> thinking did not take into account the roof structure and how it rigidly
> ties all of the walls together. =A0It's certainly not the first "duh!" mo=
ment
> I've had on this project, almost certainly not the last.
>
> Thanks to all who have replied so far, you're giving me plenty to think
> about.
>
> --
> Due to Usenet spam, emailed replies must pass an intelligence test: if
> you want me to read your reply, be sure to include this line of text in
> your email, but remove this line before sending, otherwise my filters
> will delete your email with all due prejudice. =A0Thanks!- Hide quoted te=
xt -
>
> - Show quoted text -

But then I have seen, and currently have, a double car garage with 2
8' doors that _has_ racked.  Mine is very old (don't know how many)
and has only about 1 ft between the door openings and the corners.

Harry K

RicodJour wrote:
> On Jun 28, 5:18 pm, "benick"  wrote:
>> "Smitty Two"  wrote in message
>>> In article <4...@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.
> 
> R
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.
--
aem sends...