Steel Knee Brace to stud wall 2

[13bob1313]

Hello, I have a situation with a steel knee brace coming into a wood stud wall. This is a residential balcony, I have no input on balcony design. Only being asked to size studs and advise on connections. My question is on the connection of the knee brace to the wall.

Ideally I'd like to sandwich a steel plate between studs with bolts,and come through the wall, but the architect would prefer to avoid penetrating the metal siding with the plate. The other option (see sketch) is to fasten a steel plate to the face of wall (outside OSB and standing seam siding) with lag screws into the stud wall.

My question is whether the second option is even workable. My first concern is that you have stand off distance between the steel plate and the stud, and NDS states the design values are for when "the connected members are in contact." Maybe this isn't a concern in reality, I would think the OSB would provide some bearing on the screw, and the siding is think gage material. But still, we don't have direct contact between the plate and stud. The second concern is screwing into the side grain of a stud, I'd probably require using a 6x6 post rather than (3)2x6 so there are no edge distance concerns. Lastly, it just doesn't feel right. The majority of my experience is with steel in industrial settings, so this is out of my normal range, but holding up a balcony with screws feels off (the KB load is only ~1300 lbs).

Appreciate any opinions or comments. I don't have much experience with wood, especially wood connections, so feel free to tell me I'm dumb and point me in the right direction.

 

[EIT231]

if this is an existing building - and the balcony is an after addition - there will be penetrations in siding unless you drop a column and wrap it outside wall - that being the case the open heart surgery is required and placing structure inside wall is easy and straight forward - bearing on OSB not recommended nor is it designed for those lateral loads (wind is the exception over the sheet not point loading)
you will absolutely have to look at vertical support member and possibly double the stud if not add a column - but balcony loading will dictate that design

 

[XR250]

I second the 6x6 idea. The chance of getting a lag dead center on a stud is slim to none.
If the KB load is 1,300 lbs, the vertical component is about 925 lbs (assuming 45 deg.)
I would consider using 1/4x3" simpson SDS screws - 6 ought to do it.
You also have to worry about bending of the wood column and its attachments top and bottom.
Finally, the knee brace will pull the deck away from the house. Make sure you address this.
As a rule, I always cantilever things instead of kneebrace-ing them. Much easier

 

[Lnewqban]

Consider that the location of the wall studs are unlikely in symmetry with the balcony and the knee braces; that applies to both options.
That may force you to run some anchoring beam between wall studs.
An articulated connection between plate and knee will eliminate moment and deformation of plate or poor welds introduced by inaccuracy in angles.

"Engineering is achieving function while avoiding failure." - Henry Petroski

 

[13bob1313]

Thanks for the replies, good points all. Couple things, this is new construction, so no issues detailing it how I want. Yes, cantilevered isn't an option, and that would be ideal. Stud/column has been sized for bending, and I believe I have a good handle on other load path details. I did not consider bearing on the OSB, but since the horizontal component is so small (~800 lbs) i don't think that's an issue, I'll look into that though.

My main concern is the stand off on the screws, and the idea of supporting a balcony with lag screws. But I'm not seeing any major red flags with the direction.