Non-structural Cladding & Soffit Design

[driftLimiter]

I have seen more and more projects where the structural team ends up designing all kinds of components and details for definitely non structural items.
For example soffit/fascia framing on structural steel projects. Due to the small spans, and loading of these types of elements they seem to fall well outside of normal structural elements we design. And consequently fall into a different category of conventional wisdom.

So my question is in your all experience, who is the best team to design something like this?
Should I start calling this stuff out as design by contractor, or deffered submittal maybe.

These little elements and details can end up taking more time than designing the structural system.

 

[Aesur]

I too have been noticing this trend. I'm not a fan of it and push back as I can, or ask for add services (we all know how that goes. I have been trying to limit my scope more and more by adding more verbiage defining what I am doing to my proposals, this somewhat helps get add services, but 9 times out of 10 "there is no additional money". Short of listing as deferred items or saying by contractor I'm not sure of a great solution to this never ending scope creep. I too am curious what others think.

 

[jjl317]

As a consulting engineer working in the cladding industry, I feel like we are seeing more projects where the cladding is located further away from the structure, which leads to the need for more of this supplemental engineering. Often times, it seems to be driven by thermal performance, with so many projects having 3-4" of insulation between the cladding and the structure. Not complaining, as it adds to our bottom line, but so many times I end up wondering if the EOR has fully considered all of this eccentricity. Plus, it often falls in between the cracks between the various trades, only to rear its head late in the process.

But ideally who should do this work? That is a good question. The EOR understands the complete structure, but may not be cost competitive if they include extra time to address these types of things. Outside consulting engineers may have a deeper understanding some of the cladding specific design requirements, but lack to overall knowledge of the project.

I will be interested to hear others' thoughts.

 

[Aesur]

@jjl317 - well said, this does seem to be more and more the case and as you said, typically related to energy codes. We are also seeing a lot of simple buildings being made complex due to newer architects not understanding what their pretty designs are actually doing or what they actually cost to build. Many times when the EOR puts together a proposal for a project they only have a basic description of the building and have to get to know their client over time to figure out if there will be any of these "architectural features". I for one have one client who is a 3x+ fee client due to a history of this and changes.

While I try to account for the eccentricity to the supporting structure, I have no doubt that many engineers ignore it.

It is my belief that the EOR should be designing the structure to support said components, but how they connect to the main structure is deferred as it many times may be by use of proprietary connections and the connection we design may increase the costs because we are not familiar with the specifics of that system, the system that often times isn't even known at time of design.

 

[MotorCity]

For non structural stuff, architects and contractors seem to handle it fairly well when supplemented with standard details. I think soffits generally fall into this category. Cladding I would argue is structural (i.e. components and cladding) as these elements are typically the first line of defense in resisting environmental loads. One of the litmus tests I use is "What is the consequence and risk of failure?"......If a piece of glass or stone cladding falls 200' off a building to the sidewalk below.....big problems.

 

[JedClampett]

I was at a seminar on delegated design a few months ago. I was shocked when I heard that the presenter knew about projects where almost all (I believe he said all) of the structural elements including roof, floors, shear carrying elements, etc. were delegated. Particularly the cladding or interior divider walls are commonly delegated, maybe just for the reasons you mention.
But it's a two-edged sword. There were representatives at this seminar from Building Departments who had a whole list of items that could not be delegated, such as Pre-engineered Metal Buildings (how does that work?), stairs (who knew?) and others I can't remember.
Finally, I know budgets are tight, but all you're doing is kicking the can down the road. Someone has to pay for the structural design, whether it's the supplier or the owner (to you). And if it's the supplier, it's going to take more time (once again, for you) to review the submittals.

 

[GeorgeTheCivilEngineer]

No way am I designing proprietary systems. But I do need to make allowance for them. Usually an early conversation about whatever the likely system will be and if it's changed later on then I can get a change request/RFI to bill to.