Residential Engineering 8

[xkcstructural]

So I've been posting on here cause I came from commerical and started at a residential firm.

And things are happening that I wouldn't do in commerical or design that way. I am having a hard time understanding where the disconnect it. At first I thought it was my understanding of residential design so I took the year to learn how things are done and after that year I still have the feeling that it's not up to par. Anytime I bring up something not being built to code like rebar at 3" clear cover or bolts not being installed properly (at an angle, not flush with base plate, wrong size....etc) it's "It's probably fine, it's residential loading" but then I have to write a letter saying it was built per plans and specification with out including the deviations from plan or code.

Is this normal?

 

[TheDW]

We do a ton of residential and have never written a letter saying that everything meets plans and specs. That implies that we went around measuring all of the nail spacings and whatever else they could have missed.

We will write in 'lawyer speak' saying that 'based on what we could observe it meets the design intent' or something. But never all encompassing certification that everything was done right.

 

[MyCupboard]

I have to write a blanket letters that says everything has been done and meets our plans and specifications which I find to be a little lazy and negligent. If your not willing to justify why you accepted an installation then should you be accepting it in the first place. It really is a dumb position to put people in and makes me question not residential but just this place.

Yeah, no chance I’d ever risk my license and entire career on something that could eat me alive in court - like saying something is installed per the plans and specifications when it doesn’t meet the assumptions to my specifications (things be installed in the correct orientation, etc.)

 

[Enable]

I've worked in residential only a handful of times but my experience is things really depend on the scale and type of build. My first foray was large mega-mansions when I was rather young. Those projects were reasonably well coordinated and resembled commercial builds (we often had the big deep shoring companies on them, etc). The fact that they let me lead those projects in early 20s still scares me!

Later I did some additions, and renovations (take out walls and add beam type thing). While some of the contractors were absolute rubbish, I honestly didn't feel that they were that terrible in some innate sense; rather, it's that they just didn't know when things changed enough that the way they were used to building wasn't quite the right way to go. Inertia in building practice is much more of a thing in residential in my experience. I'd surmise that's probably due to the fact margins are lower so there's not a lot of room for deviation. And as a contractor myself, I can sympathize whole heartedly with them on that score.

Anyhow what I found was that if you gave them a set of detailed prints, similar to a commercial job, everything washed over them. However, if you gave them a bare bones set of plans with key items highlighted (such as this is a shear wall with different fastening pattern in big bold letters) they tended to do it reasonably well. Now that I've moved several hours north of civilization I am starting to do a bit more residential, and this is how I am doing it. Seems to be working.

From reading XR250s posts I think this is how he approaches it as well.

 

[YoungGunner]

Having worked in residential for 7 years now, I have a few thoughts on the matter:

First off, the IRC already shows questionable engineering compared to our "big boy" design standards/codes. Before reading this thread, I was just now wracking my brain around how 1) the IRC gets away with using 1/2" dia. lag screws for deck ledgers without meeting the NDS requirement for 4D penetration into the main member AND 2) in calculating what they expect the lag screw capacity to be, I'm finding it to be DOUBLE that of an NDS calc would have, even excluding a wet factor.

In reviewing the tables for rebar in IRC foundations, the spacing FAR exceeds any limits the ACI would set and never meet temperature/shrinkage values. Whenever I calculate the strength of those basement concrete walls per ACI, they always fail. The allowable wood stud heights and spacings have always failed when I try calculating them per NDS. The IRC even allows for wood stud walls on a wider sill plate on crushed gravel as acceptable for a foundation, something I still wouldn't do.

I've also been to homes that were built many years ago and in analyzing the member strengths per NDS codes, I find that the beams should've been 100% inadequate - yet they've stood through those design-level snow storms. Come to find out, wood design is super conservative, and doing the math once, I found that a beam that technically passes by only 1% really could pass by near 300% due to safety factors, the significant penalization to most wood members due to uncertainty in quality and knots, and other factors.

And what of lateral design? Well, that one is more tricky because the 700 year wind storm and maximum considered earthquake haven't happened in my area, yet. When they do, I'll get back to you on how these structures performed.

In short - the "codes" are conservative. Super conservative. Based on my observations of the IRC, we cannot hold residential structures to the same standard as a commercial structure, nor should we - the risk associated with collapse of a single home is much less than that of a store, an office, a school, even a warehouse that is full of workers. ASCE has hard guidelines for lateral that would shut down a significant number of residential structures because the number of non-stacking walls that exist. But should a small, residential structure, with all it's redundancy, be held to the same standard as a commercial structure, which has little redundancy? I leave that open ended.

I don't think an engineer should stamp anything that they aren't comfortable with and can reason through, but to succeed in residential, you have to drop that comfort level from what you did on commercial. The more I try to compare IRC reasoning with the design standards, the more comfortable I've become with not perfectly adhering to every particular of the hefty design standards/codes, and better at picking my battles with what is more likely to fail or more likely to result in a lawsuit.

 

[xkcstructural]

I'm on board with what you've said young. But what I'm seeing is anchor bolts not being installed flush or vertical or rebar allowed to be in contact with grade.

The most basic things with out doing any design check is not meeting code requirements for basic installation and EOR not requiring the contractor to fix it and then writing a letter saying it's built to plans.

I'm still learning about what your talking about and I'm finding my level of comfort with what's acceptable design wise. I've gone down rabbit holes here and in code on prescriptive design and how we use it in our region even though we're in a high wind region over the 140 mph.

 

[YoungGunner]

I'm on board with what you've said young. But what I'm seeing is anchor bolts not being installed flush or vertical or rebar allowed to be in contact with grade.

To be fair, I think we would tell the contractor to retro new anchor bolts or pour more concrete to cover the rebar. We feel pushback sometimes with the builders, and it is frustrating when their argument is "we've been building this way for 40 years" or "I jumped on it a few times and it feels real solid - aint going anywhere." But we push back we simply won't stamp it unless it meets such and such expectations. We actually gain credibility with some of our clients for this reason, and as they work with other engineers that would allow rebar to be in contact with grade, they recognize the malpractice.

(Unfortunately that doesn't help you with your situation with your EOR. Unfortunate that they would allow for even that kind of stuff.)

 

[jerseyshore]

In my previous job, we specifically avoided calling any site visits "inspections" as that connotates that you looked at EVERYTHING. We made "observations" in the site visit letter, especially noting that we did NOT look at everything.

This x10000. Wording is very important. We had a lawyer years ago gives us a sheet of DO NOT USE words and phrases. 'Inspections' was number 1. We changed how our letters were written and it helped during issues and legal matters. I suggest a consult with a lawyer for that reason.


I also think accessibility is important in residential to getting things done the right way. If you answer your phone/ email consistently, builders and architects and owners will reach out. If you're one of those guys who takes a week to get back to someone with an answer, they are going to say eff it and build it how they want and let you figure it out later.

I try to emphasize it a lot, but I'd much rather have guys call or text me on a Saturday then have them botch the beam-to-pile connections, fail Monday's inspection, then have to figure out a repair detail by the re-inspection on that Wednesday.

 

[XR250]

I agree with everything Jerseyshore has said so far - except contact on weekends. That is a no for me. We seem to have similar clients and work, though.

@Enable - yes sir, you are correct.

 

[jerseyshore]

XR250 - well I am trying to grow my own business from the ground up so I try to be 24/7 right now.

But the idea is the same, be available so people can reach out. I did a job with an architect who was always out on his boat. Tuesday at 2 pm guys on the boat already. Then the builder is calling me for answers.

 

[milkshakelake]

I did the 6-7 days a week thing (plus working 10-12 hours per day) for about 5 years. Wasn't fun, but it got the business running. Now I have my weekends back. If I knew what I know now, I would've had weekends a long time ago, but hindsight is 20/20. If anyone calls over the weekend or during a vacation, unless it's an emergency with lots of $$ attached, it has to wait.

 

[jerseyshore]

First time I ever had this happen, but a couple of weeks ago I had a homeowner asking me to finish their retaining wall plans as soon as possible by offering additional money for me to push it to the front of the line and finish it over the weekend. I said no thanks, I'll get to it as soon as I can. I've done a million residential jobs, but don't recall anyone ever offering a "rush shipping" fee. Do other people get this and/ or actually take it? That's not a precedent I want to set personally.

 

[milkshakelake]

@jerseyshore Yeah, a few thousand to put someone's project in front of the line. Happens all the time to me. It covers overtime, and is lucrative. It also gives an opportunity of flexibility to employees if they want to work more this week but take a day off in the future. And if you meet the deadlines, the client is happier than ever. Win-win, baby!

 

[gte447f]

xkcstructural,

Yes, residential construction quality is piss poor in general.

No, you should never compromise your integrity. That includes writing letters that make statements that are not true.

I feel for you. I have been in the position as a subordinate engineer feeling pressure from clients and the boss EOR to push things through. It sucks, but you should stand up for your convictions as best you can. Like others have pointed out, a lot of it is a matter of the words you chose in the statements that you make about the construction and what you can and cannot attest to.

Some of this stuff sounds ridiculous though. For example, what the heck are you even doing on site if you see rebar laying in the dirt at the bottom of a footing excavation and you don't tell the contractor to pick the rebar up out of the dirt and to chair them up from now on?

If you are lenient, they will do even crappier work in the future. If you are strict, they may take a hint and do better, or they may get pissed and make your life miserable, but if they do, guess what? You probably won't have to work with them again. So be it.

Who is asking for these letters and why are they required? In my neck of the woods, the building permit department does framing inspections. The engineer rarely gets involved. Frankly the contractors don't want the engineers onsite because they want to be able to get away with stuff.

Also, who is typically your client? Owner, architect, or contractor? Who requests and pays for these "inspections"? In my area, nobody wants to pay the engineer for construction phase services. They just want the stamped drawings, and they never want to see or hear from you again.

 

[amigoprojects]

The residential houses are generally not in great shape when they are acquired. an inspection should always be considered whenever you go for a new place. do not compromise regarding this matter as the blame for poor quality may be given to you.