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Garage door header space

Durant

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Aug 6, 2012
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86
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Oklahoma
Installation of garage door openings, where the distance (height above garage door opening) exceeds the header size, is it acceptable to put the cripple wall below the header? Still can't get the hang of downloading pictures.
 

tmurray

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Jun 10, 2011
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NB, Canada
It really depends on what you are comfortable with. We've always allowed a couple of feet because the main load you are contending with is the roof and storeys above. The cripple wall above should not be a major problem unless it become very large.
 

zigmark

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Jan 21, 2011
Messages
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Durrant-

It certainly is acceptable to put the header at the top of the wall and frame down below it to the height of the opening.

ZIG
 

globe trekker

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Oct 19, 2009
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Durant,

I will dissent from the others on here and ask, ..what is the

size & type of beam that you plan to install over the garage

door opening?

I am dissenting, because the weight of the beam itself might

be an added weight issue on top of the cripple wall "below" it,

which could add to a non-acceptable amount of deflection over

the span of the opening.

In this locale, the cripple walls are usually installed "over" the

garage door opening beams. ;)

.
 

GBrackins

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Nov 11, 2009
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454
Location
Fairhaven, Massachusetts
if the header is above the cripple wall, then the cripple wall does not support the weight of the beam, the kings and jacks for the header support the header. the cripple wall would simply be hung from the header. would need to account for the additional weight of the cripple wall for the beam. or am I missing something?
 

KZQuixote

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Nov 9, 2010
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Location
Bend, Oregon
GBrackins said:
if the header is above the cripple wall, then the cripple wall does not support the weight of the beam, the kings and jacks for the header support the header. the cripple wall would simply be hung from the header. would need to account for the additional weight of the cripple wall for the beam. or am I missing something?
No, you're correct GB. If the wall was below the beam it would have to be strapped to the beam or have its own beam which would be wasteful. One problem with a cripple wall below the beam would be that it would not be able to resist the perpendicular loading that a garage door opener would impose, at least not as well as the beam itself could.

Bill
 

Francis Vineyard

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For those of us that are now past the 2006 IRC, didn't we have a good time with this design?

Portal.jpg


Francis
 

GBrackins

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Fairhaven, Massachusetts
in my area due to being in a 110 mph basic wind speed hurricane prone region garages are typically framed using the Engineered Wood Association's Wood Portal Frame using a continuous header at the top of the wall from side wall to side wall (with continuous plate above and below header), and of course some metal strapping, wood structural panel sheathing and lots of 8d nails. typically there is a smaller header above the actual garage doors to support the cripple wall and provide for attachment of overhead garage door.
 

DRP

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Sep 14, 2010
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Location
VA
The problem with a cripple wall of any height on top of a beam, like in Francis' picture, is that the beam under load is not laterally restrained. If the beam is up tight to the floor diaphragm it cannot buckle out of plane. With a cripple wall between the beam top and the load above the beam wants to bow outward as well as deflecting down under load.
 

TimNY

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Jan 13, 2010
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Charleston, SC
Trying to figure out Francis' reference to the 2006 IRC... do subsequent editions of the IRC require that beams be at the top of the wall? What section?

I definitely understand what DRP is saying...

Once your garage door span is over 8 feet.. and you are building a "cripple wall" below the beam... what do you think about R602.7.2?

Tim
 

Francis Vineyard

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Charlottesville, VA
Hi TimNY, for years the header was below the pony wall until as DRP aptly wrote then APA revisit the method after the '09 code change was approved to prescribed the header at the top.

Link courtesy of DRP in more words: Drop Header Design Guide



Link courtesty of APA and Southern Pine Council Help Desk can put it back where it was: APA Form J740





Francis
 
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Durant

Bronze Member
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Aug 6, 2012
Messages
86
Location
Oklahoma
It's a standard two car opening, around 16'3" I think. I'm home, saturday morning. Good Sabbath :)

The strap requirement could be a problem with the narrow walls. Don't see how the strap on the inside would reach the header and still work thru the cripple. This might be a good project for an engineer to check out. How would the cripple wall below the beam effect the PFH or PFG methods: Portal frame with hold-downs, Figures R602.10.3.3/R602.10.3.4 in 2009 IRC ?

It is clear as mud, but it covers the ground and the confusion makes me head go round. :)

I see 6 of one and half-dozen of the other. We don't seem to have a consensus.
 

DRP

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VA
I wouldn't say that off the cuff. When a joist or beam exceeds a breadth to depth ratio we require blocking or bridging, lateral restraint, to prevent rotation or lateral displacement. This is touched on in R502.7 for floors but the reference and thinking comes from the NDS, section 4.4.1 "Stability of bending members". We normally build with the top edge of beams continuously braced by a diaphragm and blocking as needed to restrain deep beams. With a dropped header there can be a situation where neither edge is really laterally braced. As the depth to breadth grows and the span lengthens it can cause problems.

A human scale thought exercise went through my head, it might help. A 1x8x10' standing upright on its edge is strong enough to support a 200lb man at midspan. Secure both ends of the beam by nailing to some framing and sling a rope over that 1x8 beam in the middle. Put your foot in the loop at the bottom of the rope and step up to load the beam. Did it simply deflect vertically or did it bow out of plane and put you on the floor? Now do it again but run a perpendicular strut to stabilize the middle of the beam in plane.

Then, think about what can happen as a cripple wall on top of a beam goes out of vertical. At vertical all load is delivered to the beam vertically. As the cripple wall slopes out of plumb the load becomes a combination of vertical and horizontal. A slightly out of plumb condition delivers most of the load to the beam vertically and a slight horizontal thrust to the beam. The beam deflects laterally in response to that lateral thrust and the wall tips a bit more, causing a greater horizontal thrust, bending the beam out of plane more, etc. It can be like a ponding problem, a self feeding loop.

Those are good links from Francis. For further reading, if you have a copy of the AISC manual handy flip to the beginning of the beam tables, there again you will find "lateral support of beams" and an explanation that the beam span tables depend on the designer providing lateral support at given intervals to yield the capacities in the tables.
 

Daddy-0-

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Oct 24, 2009
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Powhatan, Va.
Also, if you have too much tall infill framing you get into some horizontal wind loading issues especially with a side load garage where it is on the gable end.
 

Durant

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Aug 6, 2012
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Oklahoma
Francis,

I downloaded the APA J740 and it is a big help for cripple wall over the header. Does not show show cripple wall below the header.

I could not link to the other one, probably a computer problem I'm having.

Thanks
 

Sifu

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Sep 3, 2011
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1,676
I see a posible issue with the portal frame as well. A bigger issue I have encountered here a few times is the exterior cladding and what supports it. May not apply to you but I went to a frame inspection recently with the header at the top of the wall, about 6 feet above the opening. Aside from the portal frame which isn't always obvious to the builder I asked him what was going to support the brick load above the door. He said the lintel. I asked him what will support the lintel. He said he was bolting it to the beam. I looked up and said HUH? He laughed and called an engineer. Subsequently they re-built the wall. It wasn't obvious when standing inside the garage but became pretty clear when standing outside. I'll admit it was an easy mistake to make, and I was glad I caught it and so was the builder. A change in perspective, literally, changed everything. I don't think there is any prescriptive requirement for how much dead load could be carried by the wall under the header but there is for how much the header can carry on it (or in this case the member report for the LVL). I would typically want to see the header at the opening for that reason alone, plus I have seen too many "smiling" garage door headers to want to add another one to the mix.
 

Francis Vineyard

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Charlottesville, VA
Durant said:
Francis,I downloaded the APA J740 and it is a big help for cripple wall over the header. Does not show show cripple wall below the header.

I could not link to the other one, probably a computer problem I'm having.

Thanks
Just tried it worked for me! Try this search "Drop header design guide i-joist.org"

Francis
 
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