Hypothetical Use of CMU Shear Wall in Single Family Residence

[the Paper Owl]

Howdy Everyone,
I had an interesting thought this afternoon after viewing an Australian documentary on architecture. The architect had placed a CMU block wall inside of the single story house (using primarily as an aesthetic feature) BUT rotated half of the blocks 90 degrees (along the x-axis) and created a checker pattern of open blocks within the wall system. Quite cool if you ask me (even if you were to simply have one or two of the top courses with an alternating design of standard block orientation / 90 degree block orientation).

Here comes the thoughts / discussion aspect as my mind began to wander. What if you were to detail a single family residence to have an internal CMU shear wall(s), for situations where such a design element would be overkill (the wall would be built similar to a shear wall tower in multistory wood apartment construction). I am aware of the inclusion of CMU walls for certain design aspects (I have used for a gun room / safe room prior in a house). My primary question is if a CMU shear wall(s) magically appeared within your design of a typical two story residence, how would you utilize it? I envision the wall becoming the basis of beam bearing / leveraged for strength by other assemblies within the house (My first thought would be to try and brace a majority of the roof assemblies / allow all purlin braces to bear on the wall as well). In regards to design and conveying a similar feeling to east coast row homes, having an internal "exterior" wall (much like the partition brick wall found in most Baltimore row homes that I have experienced) could break up the sea of drywall. Add a few 90 degree rotation oriented blocks within a few of the courses and now we're talking uniqueness in design.

I appreciate all that have read this blurb of thoughts and in summary wanted to discuss the possible benefits of having an interior CMU shear wall(s) within a lumber single family dwelling unit that would never have such an assembly BUT because of a collection of aesthetic benefits is now a part of the structural system.

Thank you in advance.

 

[MotorCity]

In theory, an interior cmu wall could absolutely be utilized for lateral resistance. However, practically speaking, I see 3 issues from such an arrangement becoming mainstream:

1. Compatibility deformation. Unless the entire structural uses cmu shear walls, you would have severe differences in stiffness if you were to mix wood and cmu shear walls.

2. Most homes in my area, the midwest, have basements. To support an interior cmu wall, you would need a load path to soil which would require a cmu or concrete basement wall below. $$$.

3. Another trade working on the job. Most residential builders crank out houses like a batch of cookies. I would venture to say that most new home construction in my area does not require a mason. It seems most houses have siding instead of brick. Builders will use less expensive finishes whenever possible to sell multitudes of homes. If you have to bring in a mason and need to rely on your framing crew to know how to attach wood framing to cmu, any little mishap and its going to cut into the builders profits.

All that said, its certainly no unheard of cmu to be found in residential home construction, but its by no means ubiquitous. I liken it to the popularity of steel studs in residential construction...its a unicorn.

 

[DoubleStud]

Any photos of what you are talking about?

 

[XR250]

I work mostly on custom homes. Builders I have as customers would not have a problem with this. However, unless the Architect is madly in love with the idea, I would try to get wood framing to do the job.

 

[the Paper Owl]

Thank you for the input and agreed on the differential stiffness of each assembly. I had pictured a house with a sealed crawl space where this new 'full height' CMU shear wall mimics the perimeter wall design apart from the fact that it now runs to the ceiling joists in lieu of terminating at the sill plate for the first floor platform assembly.

I've included a picture below (screenshot of the video) that sparked this thought below.

 

[the Paper Owl]

Pretty unique I have to say, I don't know if I've ever seen a rotated block in a CMU wall before.

 

[KootK]

That is cool. Cost aside, I'd totally welcome one of those in my house. It would make for a great wall from which to hang my many bicycles. I loathe doing that from drywalled, wood partitions. 1/4" diameter SDS screws into the narrow faces of studs are for your house, never mine.

Certainly, if there's a basement, you'll need something under the wall other than wood framing. That could be more wall, a steel beam line, or a concrete beam line which would be my personal favorite. Really, with some temporary shoring, the wall could be it's own beam so long as it's got a couple of piers to sit on.

As you suggest, I'd exploit the wall every which way for lateral and gravity resistance. If the wall sits on a concrete beam line, it might be slick to drop that and make it wider than the block wall to provide bearing ledges for the incoming framing. If the wall is its own beam, then I guess it's bolted ledgers on either side.

Laterally speaking, the design of wood diaphragms is pretty rough stuff to begin with. I'd not turn my nose up at the prospect of a kick ass masonry shear wall running down the middle of my wood structure just because I didn't know quite what to do with it analytically. If it's gotta be flexible diaphragm assumtion, so be it.

With a basement or a crawl space, you'd need some way to get the masonry wall shear load to ground without using a wood transfer diaphragm to get that done. As such, if the wall doesn't carry down, the framing line supporting it would probably need to tie into a concrete or masonry shear wall someplace. Really, this kind of interior feature is probably the domain of the kind of rich person home that has a concrete or deck slab main floor for a diaphragm.

Another consideration if it would be a multistory building would be differential shrinkage between the masonry wall on the adjacent wood wall systems. No big deal for a one story feature though.

Yet another consideration, in seismic areas at least, would be out of plane lateral support for the wall. That should be surmountable.

The wall would add cost, no doubt about that. But, then, the heart wants what it wants and some folks can afford some of what their hearts want.

 

[Tomfh]

I would absolutely use the wall for supporting the roof and as a long shear wall.

It needs some stability in the other direction of course.