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Old 07-31-2015, 06:38 PM   #1
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Detached Garage Sheathing / Bracing


I'm about the begin building a detached garage and have encountered a few issues that are giving me a headache. Before I get into those, here's some basics about the project:

- 22' x 24' Structure
- Floating Slab w / shoulder footings
- 1 Course 6" block (8" tall)
- 2x4 Framing
- 8'8" wall height, including the block
- Engineered 10/12 pitch "room in attic trusses"
- 16' Garage Door Centered on Gable End
- Location is Minnesota
- Slab is down, materials have been ordered, but no construction yet.

Here are my issues:

(1) Because the structure is within 5 feet of the property line on two ends, I'm required to install a 1 hour rate fire wall on both sides of the rear gable and left bearing wall. My thought was that I would use exterior 5/8" firecode drywall sheathing, but not I'm confused about bracing... do I need to put wood sheathing beneath the gypsum for bracing purposes? If not required, would there be any good reason I should do it anyway?

(2) My plans have a service door very close to the corner of the right bearing wall near the rear. Do I have any narrow wall bracing concerns with this or am I okay as the rest of the wall will be covered in 7/16" OSB.

(3) On the overhead door opening gable side, I'll have 34.5" on each side of the door. Inspector is telling me I need to apply narrow wall bracing guidance, which I'm heaving a hell of time interpreting. Everything I can find on the topic shows the header extending the entire length of the wall to the corners. Am I going to need a 22' engineered header? The materials list (provided by big box store where a pro estimator helped me with materials) shows 18' 2x12s for this. Please help me understand this.

Thanks in advance for your help. I can upload a plan if that helps visualize.
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Old 08-01-2015, 08:03 AM   #2
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It does not matter what we think. The local inspector is the person who must answer these questions.

IMO, for our codes here, two 2x12's with a 1/2" plywood core bearing on at least 3 jack studs on each side are all you would need for a gable end garage door opening.

Hurricane bracing in addition to sheathing is generally notched into the exterior wall studs on a 45 degree angle from the top plate to the bottom plate. Kinda of pain to cut but really adds strength.
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Old 08-01-2015, 11:09 AM   #3
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also don't forget to have a minimum of 4' between the breaks on the top and double top plate for garage walls...
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Old 08-01-2015, 03:46 PM   #4
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Where are you located?

Welcome to the forum!

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Old 08-01-2015, 07:49 PM   #5
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You should consider getting a carpenter's help. You got your how to build info from homedepot and that worries me, a lot. I'm in NJ and there is a homedepot every 5 square miles. Not one has an "expert" that I'd ask for a definitive info. That's around 20 years, I believe.
For example, double 2x12 will not span 18'. It will dip on its own, unless there is a mid support. You must use lvl if you want to be sure. Call the manufacturer for the engineering info.
Span the header end to end, and build the narrow wall under it. Double stud each end of the wall. The wall should be no narrower than 12". Cover the wall and the header with 3/4 cdx ply on both sides. I mean the face and the back of the wall. Use the whole piece and cut out the opening. Using one continuous piece on both sides will get you the bracing. 8d nails, 4 every 12" on the header and every 6" on the studs.
BTW, I'm not an engineer, nor did I look at a table. It is something I did for my house with one wall that had 2 large openings, and passed the inspection. Take it as a starting point for your plan. Submit it as a plan and see if the inspector will accept it. Otherwise, you should get an engineer.
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Old 08-01-2015, 09:22 PM   #6
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What is the purpose of a header under a truss?

Maybe you need a header under each truss to hold up the roof?
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Old 08-01-2015, 11:15 PM   #7
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The narrow brace guidance -

maybe he was talking about this

http://www.strongtie.com/products/st...age-portal.asp

http://www.homeownersnetwork.com/boo.../wall-bracing/

something you see in CA in new garage construction for siezmic requirements.

As for the rear wall, I redid ,my garage and applied 7/16" struct 1 for shear bracing, then 5/8" drywalled over it, as my house is a 1954, and has minimal bracing ( let in bracing ), and the walls are 2x4 ad some what bowed ( sistering another stud along side helped ). I also did this so I could hang cabinets / shelving / benchtop and not really worry about backing.
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Old 08-03-2015, 01:39 PM   #8
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Thank you all for the responses.

To set everyone's mind at ease, I didn't use the big-box store for the design; I just had their estimator build me a materials list based on my specs, which I provided in my permit application and the city approved. In that plan I only had a double 2x12 non-LVL header, which they didn't comment on. They did circle the narrow walls though, referring me to a narrow wall bracing handout (same one circulating the internet, which shows corner to corner header). I've asked the city inspector, but the response I get is that I must follow the handout to a T or have an engineer sign off on anything that varies. Also, my dad is a retired carpenter of 40 years and he'll be helping me out so I do have some field know-how when it comes to the actual build. However, I am in charge of the permits and inspections and all of that stuff... which is why I'm here because I want to make sure this is done to code from planning to final signoff.

In any case, here's where I'm at since my last post:

(1) I'm going to sheath the entire exterior in 7/16" OSB, then cover the two firewalls with exterior fire-rated gypsum. This only adds a few hundred bucks and accomplish all intended goals.

(2) I'm going to go with an LVL header (double 1 3/4 in x 22') that spans corner to corner on the front garage wall with the overhead door opening / narrow panels. See attached for what I'm thinking for framing. Any feedback on this would be appreciated. FYI - I will be using 1,000 lb straps from top plate to jack stud on the interior but didn't include this on the drawing. See below for my questions on foundation anchoring.

This leaves a few more questions:

(1) I don't believe anyone answered my question about the service door. The door is 32" x 80" and will be located 16" from the rear corner on the bearing wall side. My plan with this is to just do a normal sized header for this door width and do nothing special with anchoring other than standard anchor bolts There will be one window opening also in this wall but other than that it will be continuously sheathed with 7/16" OSB. What I'm wondering is, do I have to do anything special with bracing / anchoring in that narrow section? Since the block is down I can't move the door now so I've got to work with what I've got.

(2) In my jurisdiction (Minneapolis, MN) I'm all but certain that I do need to meet the 4,200 LB hold down requirement on the narrow wall sections next to the overhead door. The concrete contractor didn't get these straps embedded into the slab because I didn't have it on my plan at the time of pour (and I'm not sure if these even work if you have a course of block on top of slab). So, I'm going to need a post-installed product that gives me 4,200 LB of hold down on each end of each narrow wall section. Can anyone give me any specific products or combinations of products that I can use for this? If there's nothing and I get flagged at inspection, I could possible have the concrete contractor install the heavy duty straps in the apron when that is poured, though he'd need to burn some extra concrete getting a large enough shoulder footing. Thoughts?

Thanks again for all of your help!
Attached Files
File Type: pdf Narrow Wall.pdf (9.0 KB, 64 views)
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Old 08-03-2015, 04:06 PM   #9
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Quote:
Originally Posted by jhaugen44 View Post

(1) I don't believe anyone answered my question about the service door. The door is 32" x 80" and will be located 16" from the rear corner on the bearing wall side. My plan with this is to just do a normal sized header for this door width and do nothing special with anchoring other than standard anchor bolts There will be one window opening also in this wall but other than that it will be continuously sheathed with 7/16" OSB. What I'm wondering is, do I have to do anything special with bracing / anchoring in that narrow section? Since the block is down I can't move the door now so I've got to work with what I've got.


Look into APA Narrow Wall Bracing Method (Google it). 16" is fortunate. Shear wall assemblies are possible down to 16" for garages with a wall height of 8,' without holddowns, I believe. You said that your plans call for 8'-8 wall height--which might need revision.

The LVL must extend the full width of the wall, and it sounds like you got that right. 22 feet? Get the specific details from your building authority. You can get it from IRC, but you might find code summaries easier to digest. There are many blogs and builder publications that cover it, too.

Make sure you know which code is adopted and which applies. I would verify the requirement for narrow wall bracing SPECIFICALLY with the authority who is going to enforce it. They should be able to answer your questions down to the letter.

Wall-bracing, IRC, Section R602.10.

(Disclaimer: I am not an engineer; a designer, commercial architecture.)
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