Shear wall design in small residential homes 7

[davidl13]

I've just started out doing my own thing on the side and working on some small residential renovations. In this case, the client wants to take down a load bearing wall and have it resupported with a flush beam (wood). I've designed wood beams before but I was wondering if there are any special considerations in terms of the analysis and the detailing for a flush beam vs. a regular drop beam?

In addition, I was wondering how to approach it from a lateral system point of view. I don't have any existing drawings and the house is inhabited so I can't just request to open probes anywhere I want. I don't have that much experience with residential construction, but I assume that any load bearing wall must also act as a shear wall. Is there any way I can justify that ripping down this wall won't have an impact on the integrity of the lateral system in general? Typically, these homes may have been overdesigned and maybe I can justify it numerically that it would still work if we reduce the total length of the shear walls by like 10% for instance?

I'm asking strictly from a safety point of view, less from a permit standpoint.

Any comments/advice would be greatly appreciated!

 

[GaStruct]

I don't care and it doesn't legally matter.

Irrationally hostile response. Take it up with Terry Malone lol

You can't produce an unsafe or inadequate design to ensure a profit on the job.

That is literally the point of the post and the book

 

[Eng16080]

If this were a hypothetical question, then sure, fine, that exceeds the standard of care, asking about something you don't know how to do properly, but in this case, the project has already been agreed upon, the assignment accepted, and now the most basic questions are being asked. I'm not on board that that is "exceeding" the standard of care, and I never will be.

Perhaps I should not have mentioned the term "standard of care" in my comment. I was merely making an observation that from my own experience, it appears that many, if not most, practicing engineers in my area who do residential work give little consideration to lateral design. I'm not saying this is right, and I'm not saying that OP should proceed in this manner. Also I'm not a lawyer, and I'll admit I'm not entirely sure what "standard of care" really even means or how a jury might interpret it.

What I do think is that most of these other engineers who are creating potentially negligent designs aren't on eng-tips or elsewhere trying to fill in their knowledge gaps. Most aren't asking these questions, nor do they likely recognize their own deficiencies to begin with. Everything considered, just by asking the question, I'd consider OP a better engineer than most.

Another thing is that it's often incredibly difficult for an engineer to even realize where their designs might be deficient. Getting meaningful feedback is not easy in this profession. Buildings rarely fall over, and most engineers don't get to work for the perfect company for 10 years under the perfect mentor before starting their own practice.

For residential work in particular, if it's true that those of us who are more attentive to lateral design tend to lose bids to those who aren't, then the unfortunate outcome will be that most engineers doing residential work are not considering lateral design. And then, most firms doing residential work are not considering lateral design. And finally, most new engineers hired by such firms are not being taught this aspect of the design properly and are not considering lateral design.

I'm generally happy doing residential work, and I fully agree with the comments here concerning how complex it can be. I've occasionally had conversations with other engineers who don't think residential is "real" engineering and I've never understood that. I'll typically spend more hours on a 5,000 square foot luxury home than a multi-story office building with the same footprint on every floor. But yeah, it definitely sucks when I have a two and a half story cathedral wall facing the water packed full of steel and LVL framing while the last engineer did the same thing with a couple 2x6 walls stacked one on top of the other.

 

[rabuilt]

Consider a copy of the reference below. It's gross overkill for most of what I do but, at the same time, pretty much everything that you might want to know about light frame wood lateral systems is in there.

It's like having the bible close to hand when your immediate concern is really just whether or not to kill your neighbor.

View attachment 2244

This is a great resource... I highly recommended it.

 

[XR250]

I was merely making an observation that from my own experience, it appears that many, if not most, practicing engineers in my area who do residential work give little consideration to lateral design.

But yeah, it definitely sucks when I have a two and a half story cathedral wall facing the water packed full of steel and LVL framing while the last engineer did the same thing with a couple 2x6 walls stacked one on top of the other.

Ever since the 2018 IRC, we are required to do a rudimentary lateral analysis. It is something they typically check during plan review. Honestly, I know of zero instances of a lateral failure in my area so even the 70's all-glass modernest, non-engineered houses seem to be performing adequately.
We have a few engineers who would be doing those tall gables with 2x4's!

 

[Enable]

 

[KootK]

what you said reads to me like you don't care about competence or experience, I don't see how that can be read any other way

Then it seems that you are not a very strong reader.

Competent engineering is important but a distant second.

Basically an admission that you've routinely practiced outside your area of competence.

Absolutely. What, am I supposed to put a pin in myself and grow no further just because I'm practicing independently? Fat chance of that. If I'm a lot out of my depth, I engage competent help. If I'm a little out of my depth, I sort it out myself.

Where did you say you were practicing again?

Alberta, British Columbia, Ontario, Nova Scotia, Washington, Oregon, California, Colorado, Wyoming, Iowa, Wisconsin, Ohio.

 

[EngDM]

I hate it when the parents fight.

 

[KootK]

This attitude is dangerous and negligent and I'm asking you to stop advocating it.

Hard pass.

I share my candid views on such things precisely because I feel that our profession tends to be opaque when it comes to how the practice of it really works. And I feel that we do one another a disservice when we are not forthright about that.

The fact that someone such as yourself would quote a zillion lines of legalese in the context of this conversation is precisely the problem in my view.

Here's how all of those lines of legalese came to be:

1) Engineers decided that they wanted a pseudo monopoly over their work by way of licensing. And, to a lesser extent, they wanted better public safety.

2) Engineers created / influenced the associations to produce the current set of rules which increase public faith in the profession and justify the monopoly.

3) With the monopoly nicely in hand, engineers take some liberties, as they always have.

It is a fine thing that our monopoly and public safety are able to march somewhat in lockstep this way. But it is a myth that engineers were just hanging out, minding their own businesses... and along came a regulator. That's just naïve.

The practice codes are who we wish to be in the eyes of the public. Who we actually are invariably falls a bit short of that.

 

[KootK]

hate it when the parents fight.

Meh, it won't be worth running for the popcorn.

It's impossible to really prove anything in space like this that is non-technical. So it basically ends at an exchange of viewpoints.

 

[rabuilt]

With just words, not image, not dimension, it's really difficult to answer this question. That said, there are some alternatives that in employed here that could save the problem. Keep in mind, I work in the northwest, and we never have 2x4 construction for residence... insulation requirement requires the volume of 2x6 walls.

The problem with these "prow" front or big window and no wall is there is no way to get a lateral system to hold the roof diaphragm in place during wind and seismic events. However, if you meet the criteria of a 3-sided diaphragm, you can resolve the later system that way. Another way I've done it is with cantilever diaphragm. If there are interior walls that can be used for shear wall and meet aspect ratio, they can be design for the lateral force. if all else fails, then there are Simpson strong walls. Depending on the load, you can use 12", 18" or 24" panel to resist the lateral forces.

These methods take a little more time to resolve, and the budget needs to be there for that. If I lose out on an opportunity because my estimate is higher, so be it. I would make it clear in my proposal so the clients understand. Secondly, I will note this via a phone call or email.

 

[XR250]

1) Engineers decided that they wanted a pseudo monopoly over their work by way of licensing. And, to a lesser extent, they wanted better public safety.

2) Engineers created / influenced the associations to produce the current set of rules which increase public faith in the profession and justify the monopoly.

3) With the monopoly nicely in hand, engineers take some liberties, as they always have

Hmm, I never considered this and I don't buy it. How is our profession a monopoly? Do you want any random yayhoo designing structures?

 

[KootK]

How is our profession a monopoly?

I described it as a pseudo monopoly. That, because one dimension of professional licensing is market protectionism. You can charge a bit for a thing if doing that thing requires a credential that is difficult to acquire. This is the case with most, if not all, licensed professions.

Doctors are constantly complaining about being overworked. They are overworked because there are not enough doctors. And there are not enough doctors because their profession deliberately keeps the pool of doctors to a restricted sized that keeps their salaries high.

Same goes for lawyers, aestheticians in Illinois... so on and so forth. To an extent, a professional gets paid in proportion to how hard their license is to acquire.

As the state has a monopoly over the use of violence, so license structural engineers have a monopoly over the use of ETABS.

Do you want any random yayhoo designing structures?

No. Ideally it would be just me.

I never said that I wanted the licensing to go away. I simply want our community to have a healthy and accurate understanding of how that system works.

 

[XR250]

You can charge a bit for a thing if doing that thing requires a credential that is difficult to acquire. This is the case with most, if not all, licensed professions.

Absolutely. So what? I don't want my Doctor to have had an easy time getting his license.
Many licensed non-professionals make nearly as much or more than I do - such as building contractors, plumbers or HVAC peeps

 

[KootK]

Absolutely. So what?

So doctor salaries are artificially inflated by their deliberately restricting the pool of doctors through licensing and medical school admission policies that may be more onerous than they need to be. And that's the pseudo monopoly.

I don't want my Doctor to have had an easy time getting his license.

Me neither. You keep erroneously suggesting that I do want licensing for doctors and structural engineers to be easy or non existent. I don't. I personally benefit from both the public safety and market restriction aspect of licensing.

That said, you have no idea whether the rigor imposed incoming doctors is at the appropriate level, too lax, or too high. As a consumer, you simply trust them to set their own standards appropriately and you pay what they tell you is justified by that. Such is the benefit of the pseudo monopoly.

Many licensed non-professionals make nearly as much or more than I do - such as building contractors, plumbers or HVAC peeps

So what? There are lots of ways to make money and the economics of all of those activities have their own nuances. Have a license. Have special knowledge. Work crazy hard. Sacrifice time from your family. Join a union. Do something dirty (literally or societally).

Other fields having earning power doesn't, logically, change the situation of how we have come to have some degree of earning power.

 

[GaStruct]

As the state has a monopoly over the use of violence

Nice to see someone else who has read Murry Rothbard

 

[Envelope3]

NO. This attitude is dangerous and negligent and I'm asking you to stop advocating it. This is the "fake it until you make it" and it does not ethically fly in engineering. I'll unhappily point to OceanGate (six dead was it?) and Harbour Cay (11 deaths as it happened during construction), the Kansas City Hyatt collapse (114 deaths), and Berkmann Plaza II ("only" one death, again, during construction) where the record is quite clear, and we can put the FIU Bridge Collapse (6 deaths, again, during construction), and Champlain Towers South (98 deaths) in the at least maybe category where four out of five dentists think there were issues that were fairly obvious.

x2 From time to time, I get into engineering liability cases involving failures and engineering negligence, and after reading the OP, I question whether or not it deserved reporting to an engineering board. At a minimum, eng-tips probably needs to take the thread down. It's one thing to ask a targeted engineering question but the OP seems to be laying out a background that I have seen backfire.

 

[KootK]

I would like to see this forum remain a safe space where any engineer can ask anything without fear of being reported to an engineering board. All that would achieve would be to drive people into the shadows where they do not have the ability to query their understanding as they do here.

 

[Eng16080]

. . . after reading the OP, I question whether or not it deserved reporting to an engineering board

That's going way overboard!

For almost any question asked on this site, I'm sure there's somebody who would find it outrageous that another engineer would ask such a thing. In my experience it's the people not asking questions who are usually creating problems. You're better off reporting engineers/builders responsible for these massive window walls framed with 2x4s. Even then, I guarantee nobody will care unless there's an actual failure.

The few times I ever reported something sketchy, where the builder was clearly in error and I was truly concerned, it was like pulling f*ckin teeth trying to get anybody to do anything about it.

 

[Envelope3]

Had he not presented the background as he had, I probably would feel differently. He is literally laying out that he has no experience in residential design but is going for it anyway and then following up with an EIT question on an internet forum.

He better pray he's not practicing in Florida; they come down hard on this kind of scenario.

 

[EngDM]

Had he not presented the background as he had, I probably would feel differently. He is literally laying out that he has no experience in residential design but is going for it anyway and then following up with an EIT question on an internet forum.

He better pray he's not practicing in Florida; they come down hard on this kind of scenario.

Different strokes for different folks I guess. Coming from a commercial backround with very little residential experience (aside from treating shearwalls as engineered and moving on with my life) I found a lot of the replies pretty helpful, even got a fight better than Tyson v Paul out of this thread. Prescriptive design is a whole other beast and can feel like the wild west/unconservative at times, so at least from where I stand OP's questions are reasonable, and nothing appeared to indicate that they aren't qualified to do this work; they're doing the due diligence and using this forum as intended.

The fact that this thread is this long and this controversial over residential is insane.

I was going to go through a bunch of y'alls thread history to find some pretty stupid questions to prove my point, but that's just me being petty.