Multi-wythe brick wall retrofit loose lintel - how do the jambs work?

[bones206]

Architect is adding windows to an existing non-bearing & non-lateral exterior wall with clay brick on the outer faces and solid 4" CMU brick for the interior wythe. It's easy enough to shore the wall and add some loose lintels (3 angles in my case), but what's the magic trick to create jambs and transfer mechanism for the out-of-plane wind reactions from the exterior lintel?

The architect is averse to any kind of brick reconstruction/toothing-in due to concerns about matching mortar etc. They just want to sawcut the opening and stick the window in. So this obviously limits what I can do with the jambs. I can probably negotiate this point if rebuilding the jambs is an absolute necessity, but I'm looking for any tips or tricks out there so I can at least say I've exhausted all options.

 

[XR250]

what are the dimensions?

 

[bones206]

This is basically it. There are some other details that complicate matters, but I don;t want to muddy the waters too much in hopes of keeping this topic a little more generic. I realize there is probably a certain size opening where a supplemental steel frame is warranted, but for the sake of this question I'm more interested in any lower cost solutions that people use to make the numbers work on something like this.

 

[KootK]

Mostly radio silence here...

What lame ass "tricks" there be are these:

1) Assume that the wind load has a competent load path from window to jamb, which it likely does not.

2) Assume an effective width of unreinforced masonry pier to use as the structural jamb. Here you can surely have most of it at mid-height.

3) "Design" the jamb using P/A + M/Sx unreinforced masonry design principles that probably won't work.

I'm not suggesting that I'm holier than thou and don't do this kind of stuff myself. I'm saying that this is how I know it to be done.

Another useful "trick" is to lay claim to the use of "engineering judgment" in a situation where that judgment has never actually be validated via numerical calculation. This one approaches the level magic that you seek.

 

[Enable]

I have two, admittedly not great, options for consideration.

Option A: Corner Angles

What's the clearance between the window and the opening? If you have at least 3/8" for caulking you might be able to get a 1/4" angle to act as a cleat underneath the loose lintels above. Connect the angle to existing masonry with epoxied threaded rod (weldable so you can plug weld it to reduce protrusion into opening). Not super duper but low profile that should be okayish for nominal loading. EDIT - Length of anchor was shown as relatively small but I was thinking you go far enough back to grab several bricks/blocks. Maybe add two or three relatively small anchors to facilitate greater epoxy binding.

Option B: Spira-Lok Helical Ties

If you put enough of these guys into the masonry above the window opening, perhaps you can consider the masonry above the window as a beam of sorts for the out of plane wind loads. You might consider drilling vertically (from within the opening) as opposed to horizontally since the load application is orthogonal to the usual direction. This has the added benefit of not going through the mortar on the outside, which a horizontal application entails.

EDIT - Also should have said to add the ties into the masonry jambs from inside the opening.

 

[XR250]

Another useful "trick" is to lay claim to the use of "engineering judgment" in a situation where that judgment has never actually be validated via numerical calculation. This one approaches the level magic that you seek.

That made me laugh

 

[XR250]

I suppose if you assume the wythes have some composite action, KootK's idea of assuming a trib. width of the jambs might pan out for 12" masonry.
You could chip out the CMU in the jamb where accessible and add rebar and grout. Won't get you all the way to the top but maybe you could reach the bottom if you are determined.

 

[bones206]

I like all the ideas presented, especially the engineering judgment one since it simultaneously solves my problem and feeds my ego. I ended up dealing with this by taking out the entire center portion of the wall from floor to ceiling, then bracketing that opening with full height C5X6.7 jambs. Infilled with CFS framing with proper header and sill anchored to the C5 jambs. The architect is going to wrap it all with something fancy and make it a feature. But I'm still interested in the problem from a general standpoint as I seem to be working on a lot of old brick buildings these days.

I did look at the helicial ties and I think that will be my preferred choice in the future. I just couldn't use it for this case because there's also a W24 beam coming out of the page that limited the lintel height to 5". This thread (thread507-506678) had some good discussion brewing on the helical ties. It's still not closed if people want to explore the tie idea further, especially as is pertains to multi-wythe. I think I would have needed something like that to make the wythes act together compositely.