Industry Interview with Structural Engineer Rhett Schaefer of Rice Engineering

Industry Interview with Structural Engineer Rhett Schaefer of Rice Engineering

In this Industry Interview, Monarch Metal CEO Brandon Bingham speaks with Rhett Schaefer, Structural Engineer with Rice Engineering , one of the nation’s leading engineering firms specializing in exterior cladding, curtain wall, rainscreens and sunshades, and more.

Can you please tell us about how Rice Engineering got started and where it is today?

It started off with Dave Rice who had years in the curtain wall industry, thermal engineering industry. And he opened up a business basically out of his attic. And he was just a one-person shop with basically two clients doing curtain wall calculations.

So that’s where we started off and he incorporated it in I believe in 1999. And kind of moved on from just curtain wall to doing hand railings calculations, sunshades, panel systems, obviously the curtain walls, well still window wall. Basically anything that’s cladding, we have a hand in providing engineering calculations for it. So it grew from that one-person shop to today we have roughly sixty employees and forty-five engineers on staff.

Pier 17, New York – Rice Engineering

When do you typically become involved in a project and who among the project roles typically hires you?

So when we typically are involved in the project, it’s usually after the architectural drawings have been submitted and projects are going out for bid. So I have a few clients where we’ll perform preliminary engineering for them. So they can provide more accurate bids for the project and usually that’s like with a clip type system, like a clip and rail rain screen system. Or we can provide a good rough idea for ninety percent of the building, what your clip spacing is going to need to be. So that is a few of the clients, but mostly it comes from after the project has been awarded by a client, then they come to us to perform the engineering calculations on their product they’re providing. 

And typically who comes to us, is, most of the time it’s either an installer, or a manufacturer. Those are your two largest, we’re rarely ever hired by architects directly.

Can you tell us about the testing standards you typically reference when working on a project?

So, the thing with the testing standards are, there is a testing standard, or an ASTM, for anything you want to put out there. So typically we aren’t really referencing, us personally aren’t referencing the standards. Usually they’ll be included in the project specifications say this curtain wall system needs to meet the E330 or water infiltration testing. So usually that’s provided by the project specifications which is directed by the architect or, whatever the manufacturer wants to provide for a specification for the product. So it’s hard to pinpoint which one you would really need to use, I mean ASTME330 which is the standard test method for structure performance of exterior windows, doors, skylights, and curtain wall systems. And we don’t really have a good one for like stone panels or fiber cement panels for testing standards so we typically follow those same testing standards.

It is the standard test method for structural performance of exterior windows, doors, skylights, and curtain walls by uniform setting air and pressure differences.  So basically it’s just the air and water tests for those types of systems. And that’s usually what you’ll use for when you perform a wind tunnel, or not a wind tunnel study but actually doing performance testing on the components. 

Can you please talk about the difference between finite element analysis and systems analysis and which each is suitable?

Okay so finite element analysis, or FEA models, is basically you’re breaking down the component into, hundreds or thousands, of small, I guess, pieces if you will. So you’re breaking down that whole element and it’s going to be into thousands of different little, tries to make it a cube or trapezoidal shapes. And what it’s doing is the stresses are sharing and how they’re interacting from each individual node and shape throughout the entire component. So it’s a much more accurate analysis of how stress is transferring through a component. 

So when we would use that is more so when it’s difficult to determine based off of simple static calculations that are provided to us by the steel code, aluminum codes, or anything of that matter. So when we typically have to run a FEA model, is when we have perforated panels that are unique shape that have unique patterns like I’ve had a panel that is in the shape of a leaf, they did a perforation pattern in the shape of a leaf.  Well it’s really difficult to just kind of determine how that load is going to transfer through there, so we run models that will show us our stresses and deflections and shears through the components.  So it’s really when we get into complex geometry that we use that FEA modeling.

Brandon: And then the systems analysis would be something like when we bring you our cladding substructure to hang like a Trespa or Fundermax panel then?

Exactly we have basic calculations provided to us by codes and then just by pure, static calculations, and some the stresses that are backed up by testing that they were able to provide theoretical calculation for. So like a weak axis suspending of a bracket, which is what we would typically do, deal with Monarch is with the, just do the L-rail for instance. We have calculations, I’ll check the whole section for bending, torsion, shear, tension, and that we can also do the local flanges for their bending through just the individual components of the L profile. And that’s where we can use that analysis. 

However, like a job I actually, someone else at Monarch had sent over about perforating that L profile, that’s where we might be now going into FEA modeling to more accurately determine the structural adequacy of the system. 

Brandon: Yeah that’s a great example they’re trying to achieve some type of open rate and you need to now analyze because the property has changed for the L rail. 

Exactly and it’s difficult to determine so we have dead load hanging out there and we have to make sure it can hang, hold that weight. But now instead of having a solid material, you now have twenty percent of material taken out of the L profile. So how it’s not going to be a direct transfer from the front of the L profile to where it’s attached to the bracket. So now we kind of have to go through a modeling software so it’s not as conservative of a check because if I was going to check it with typical methods or typical statistical methods, I would have to reduce the section properties of the material by a considerable amount to be conservative to make sure that we’re not over-stress at those areas. 

Can you tell us about the variables you consider when you recommend fastener spacing for mounting rain screen panels? Such as negative pressure, panel material size and weight, fastener pull-out values. How does that all come together to give you the spacing variables? 

Well it’s not the best of answers but it really depends on what kind of system we’re using to hold up these rain screen panels and what type of system the rain screen panels are. If we’re talking ACM panels, aluminum composite panels, or aluminum plate panels that have perimeter extrusions and clips. Typically those are designed from the panel manufacturer that the clips and the perimeter extrusions will not fail before fastener pull-out. 

So typically when we’re seeing that we’re just making sure that those, it’s really about the load transfer. That’s the main thing to figure out what are fastener capacity is going to be, how load transfers through the system.

Yeah so the components that we have to go through to determine our load transfer is of course all of those that you mentioned and the negative pressure. Positive pressure typically isn’t the issue because most of the time that’s just going to be bearing, substructure is going to be bearing directly into the structures so it’s not so much tension unless you have a high weight hanging off the building. 

But then you have panel weight, how far that panel weight is set off from the attachment of the fastener. So if we’re three inches out from the building or twelve inches out from the building, that is a much bigger difference on the tension on those fasteners attaching the substructure to the structure.

And then fastener pull-out capacity is obviously the largest function of, how or what we’re looking at for the actual fastener performance. 

Brandon: So the fastener is what we, as a building person, we’d want to make sure the fastener’s not going to fail?

Yeah essentially, as a building person yes but when you’re providing the brackets or the profiles you’ll want to make sure that the fastener is the weakest part of the system, right? So it’s just a balancing act that way. And it depends on, again how the load is transferred back. So you have a bracket with a back flange of say, four inches wide that’s attached back to the structure. And the fastener is installed right in the center of those four inches. Well, depending on how the load transfers, that could be more tension on the fastener than say if it’s one inches over from the web of that bracket. So that’s just extra eccentricities that we need to determine when looking at the fastener capacities as well. It’s not like you’re putting up your vertical L profiles in your brackets. That’s going to be straight tension based on the wind load in the area. That is not necessarily what’s going to be the tension on the fastener. There may be added tension on the fastener because the load isn’t lined up directly over the fastener. 

What type of safety factor do you typically plan for when engineering a system? 

Okay again, it depends on the system, what’s the defining factor is, what type of failure mode will the system have? So if we have a brittle failure, or a sudden failure, like you would have with fiber cementitious panels, or especially stone panels like limestone or a quarry product. Well a quarry product is going to differ greatly from one quarry to the next on what mechanical properties that stone will have. So there is where we would use like a factor safety of eight. On the bending strength of that material just because it’s so varied.

Products that are manufactured, like a terracotta panel, or even the fiber cementitious panels, they’re actually manufactured in a shop. We can reduce that safety factor and per all the codes, to maybe anywhere from like three to five, just depending on what kind of panel system it is. But that’s because it’s a manufactured product, it’s more predictable what those values will be for the modulus of rupture, bending strength, shear strength, and tensile strength of the material. And then again pull-out values for the fasteners. 

So, in aluminum, that’s not going to be a sudden failure. You’ll see if the aluminum profile were to start failing it would start yielding first. So since we have more of a flexible material that has a yielding failure but wouldn’t meet its rupture quite yet, we only have a safety factor of 1.65 as indicated by the aluminum design manual. Because again it’s a more predictable material, there’s so much design that goes involved with all these. And we have a good idea of how this profile will perform. 

Some people may not understand what a safety factor is. Can you give a layman’s definition of that?

Okay so safety factors, we do everything in allowable stress design. What a safety factor is, it’s taking at number that this panel will break, or will exceed its bending stress at three thousand PSI. Alright we apply a safety factor, so you divide that ultimate three thousand PSI divided by, so we have a safety factor of four, divide that by four, well let’s do three make it a little easier. Then we’ll only be holding our stress value that we can bring it to a thousand PSI. 

So essentially all we’re doing is making it so it’s technically three times, and I don’t want to say over designed but, you would be less likely for you to see a failure because we’re not taking it to its ultimate failure value.

Can you tell us about the difference in planning with a metal stud wall versus a CMU or a concrete wall?

Yes so, metal studs, typically we’re assuming we can only have attachment either from sixteen to twenty four inch horizontally on-center, that’s typically what we’ll see for range. And we like to assume sixteen gauge studs, because that gives us a better pull-out value. We get a pull-out value for a quarter-inch fastener of around two hundred and sixty to two hundred and eighty pounds. When you go down to an eighteen gauge stud, that same fastener only has a pull-out value of around 130 to 160, let’s say, pounds per fastener. So that’s quite a big dip in capacity. So when you’re securing to eighteen gauge studs, you’ll have less capacity and then therefore closer spacing vertically because we can’t change the spacing horizontally, right? So you’ll have different spacing vertically because you’ll have so much less capacity in your anchor, just because it’s a thinner material essentially. Even though the engineering firm that’s providing the studs, they will meet the wind loads and everything else, but are they really accounting for clip systems being put ever forty four inches vertically along the stud? Most likely not. 

And then when it comes to hollow block CMU, that’s usually the worst condition we have. You can only account for one in a quarter inch minimum embedment at most with fasteners; most of them are designed for only one inch minimum embedment. So we’re only looking for hollow blocks CMU of pull-out strengths of between a hundred pounds and 150. Because CMU anchors have to have a safety factor of five, it’s such a variable building material you’re anchored into. 

So therefore again, if you’re installing into sixteen gauge studs versus hollow block CMU, well that hollow block CMU will have much closer spacing of a bracket system. 

And then grout-filled block you can get a lot better capacities because we can put in, embedment depths much deeper. So it just depends on what anchor and each anchor will have different values that we’re using, CMU anchors. For grout-filled CMU, they will have a lot of ICC report testing and ESR reports. In hollow block there’s only a couple that I can think of, that have the ICC reporting. And then into concrete, so there’s, [laughter] this kind of came when I first started here at Rice maybe five years ago; we were finding in the codes that where your design assumed cracked concrete. So that means and I’m not saying that you see a visible crack in there you’ll see an inch deep, inch wide crack. I’m talking about micro cracks that you can’t really see with the human eye inside the concrete. This is occurring when the concrete is in tension zone. So if you have a wall and it’s loaded from the backside, well it’s going to want to flex. And the inside will be in compression, the outside will be in tension. Concrete’s poor in tension so it has a tendency to do these micro fractures, unless the concrete’s designed with the proper reinforcement to prevent this. 

So the code tells us we have to assume cracked concrete, when we’re designing concrete anchors. And those are much more expensive anchors, they’re much beefier anchors but they allow for the seismic zones too. Any anchor into like a seismic category C or D is going to have to require you to be cracked concrete approved just because the, you’re going to see seismic activity in that lifetime of that structure.

So that was the biggest change the contractor saw when we used to be able to call out these small quarter inch fasteners that will only need to go in two inches deep. Well now you have ¼ inch maybe, but those are also going in 3/4 inches deep, or even, much larger anchors. 

The only way we can get around that from our aspect of design, when we’re in the design is going back to the architect or engineer of record and seeing if they will allow us to use non-cracked concrete anchors. Typically that’s difficult to get past because it’s hard to prove that concrete will not experience cracking in its lifetime.

In wall bracket systems like Monarch’s, can you tell us about the static load versus wind load with brackets?

Okay, yeah so like with Monarch’s brackets you have a double bracket, let’s say roughly a little over six inches long, and then the wind load bracket which is only roughly three, three and a half inch, Brandon: six and a half and three and a quarter, Rhett: Okay perfect.

And so when we’re laying out these types of clip systems, the whole idea of these rain screen systems, if it’s a vertically running system especially, is that it accounts for thermal movement. You will have clips along a vertical wall, say we’re running a rain screen system, we’ll just say fiber cement panels for instance. And we’re attaching to these vertical L profiles. Well that vertical L profile for aluminum, anything over ten to twelve feet, is starting to get to quite a bit of thermal movement. So that’s what we like to limit our vertical spans ten to twelve feet. Also we don’t like to span over building deflection joints because the system cannot accommodate somewhere up to three quarters of an inch movement vertically each direction. It’s not going to allow for a total of one and a half inches of movement. It allows more for just the thermal which can be just roughly like a quarter-inch expansion, quarter-inch contraction. So when we’re designing those types of systems, the reason why we have a dead low bracket, which is the double bracket, is it’s six and a half inches long, is because that will be handling the whole weight that is imposed upon that vertical profile. So it will be holding the whole weight of that component. 

Well since we have the six inches there, we can through-fasten that profile to that clip instead of installing it into slots, because we want that just to be held in place. That is the point where we’re not going to be, able to allow any thermal movement all through a movement will have to be driven from that dead low bracket, either upwards or downwards. We like to stick with one bracket per profile that’s a double bracket or dead load bracket, because we want to make sure it accounts for that thermal movement over those ten feet.

If every single one of them were to be dead load brackets, then there would be a no-allotment for thermal movement and you could have issues because the profile is going to move. Thermal is a very powerful force it’s going to have to move somewhere, so it’ll either try to bow-out or bow-in. We just want to prevent that by allowing you to have movement from that dead load bracket. So the reason why I need to be deeper is because we need more fasteners to hold up the dead weight of the structure, since all that panel is being held on say one L profile or two L profiles. 

The wind load clips are smaller and have slots. Those we need to take wind load in and out so they’re taking less load of the system. So they typically can be smaller lengths because we don’t need to take as much flexure, they won’t be taking as much flexure or moment force through. So we’re installing those fasteners from the L profile into the slots, again, to allow for that thermal movement. There is no reason why we need to dead load the entire L profile. And it’s more of a waste of material if we’re calling out double brackets for the entire length of profile and more than likely we’re not going to need it for the wind forces.

What are the common design considerations for planning for strapping?

So strapping so we’re talking about say two to four inch tall, light gauge, strap going from stud to stud, to bridge the area in case you need to throw brackets in between stud spacing. So the issue with strapping is those thin gauge flat plates are horrible for deflection and horrible for stresses. Typically the only ways to get those to work if you’re installing after the sheathing has been installed, so we’re installing it right over the sheathing, is you would have to look at it as a tension member. So we’re pulling out with, I would say in the center of that span on that strap or pulling out on that, it’s going to restrict that deflection, it’s going to send really high shears into the adjacent fasteners into the studs. So you may need three or four fasteners at each stud location to account for those shears. Who’s really going to be putting in four fasteners per stud per strap? It’s not very realistic and it may overload the stud that we’re not designing. I mean studs are usually by others while we’re doing these so someone would have to check that down the line. 

The best way when we’re allowing for strapping is if you can get it installed, directly to the studs, in between the studs and the sheathing. Because then we have that sheathing to help with the deflection issues when we’re pulling out. You have so much rigidity and that sheathing to help with the deflection of that strap. So if we’re designing 18 gauge straps that are spanning 16 inches, we hardly could ever get that to pass through our calculations because it’s usually going to fail in stress, bending, or deflection. When it’s behind the sheathing, then all we really have to worry about is getting the stress to work. Which is a little bit easier than a deflection because there’s just no depth, there’s no depth to a strap. So that’s why it’s so poor for deflection. If we have to call out straps over sheathing, it’s not going to be like it’s a 16 gauge material. It could be up to ⅛ inch thick steel, 3/16 inch thick steel, it just doesn’t make sense. It’s just too thick, too beefy, of a route to go with that. It just doesn’t seem like it’d be cost effective to go with that strap. 

Yeah I mean again there’s ways we can get them to work but, again, they would have to take really high shears. And I don’t know if it’s realistic to expect them to be installed where they’re going to have that many fasteners per stud, per strap. Also the other thing thinking about those straps is, okay we’re spanning over the sheathing and waterproofing. If we’re installing fasteners between studs, well your fasteners will now be penetrating the vapor barrier and sheathing between studs so therefore you’d have to worry about more waterproofing. Because when that strapping deflects, and comes out, it’s going to pull away from the sheathing. So it’s very difficult to then waterproof behind those fastener penetrations.

That’s why it’s a little bit easier again when we have a strapping between the stud and sheathing because it would deflect the same amount with the sheathing or it’d be so rigid it won’t deflect.

What are the design elements that you see architects maybe not get right that you’re correcting when plans come to you? What are some of the major things you see?

Alright so what we typically see, and I’m coming from panel standpoint and rain screen system standpoint, there’s plenty of others with curtain wall and sun shades but, typically it is, when we’re seeing the architectural drawings, they’re not fine details, so we have to, not necessarily change things to make them work but add more framing, or sub-framing, or stiffeners to make the items work. So like coping panels, panels around a knee wall at the top of the building parapet. So those will be spanning 10 feet long, and they will not allow for, they’ll be held from uplift of the ends, but on the front fascia, there’s nothing preventing uplift. So you have to rely on these clips that are 10 feet apart from each other to prevent uplift which can be upwards to 70 PSF. So we have to either change how we’re attaching those coping panels to allow prevention of uplift along the fascia. Or provide Z keepers just hold them in place. 

So that’s from a panel standpoint that’s the largest one I see and deflection joints as well as installation of panel systems spanning from floor-to-floor, over floor deflection joints. Those floors have to allow for some kind of movement. So typically as an engineer what we like to see is the sub-framing systems or the panels do not span over floors so you don’t have to worry about bridging that deflection joints. Because once you bridge that to the floor deflection joint, if that floor were to move down, well you’re going to shear through your fasteners more than likely that’s holding that together. Or something else is going to be an issue, all buckling of your vertical frame members or whatnot. A lot of issues can derive from that and sometimes it’s caught, sometimes it’s not, or more it’s the engineers’ challenge of that delegated design to figure out a solution. So we just like to say again, start and stop, have four lines, you wouldn’t have as much of an issue, or there’d be no issue.  That is the largest thing we see. 

And then after that it’s just more typical detailing maybe they’re not preventing disengagement just how they’re drawn. So like again it’s like with the coping panels or we have a fascia panel that returns to soffit, well is there anything really preventing the disengagement of the system from negative loading? That’s the common things that we see that were not caught in architectural work.

But for rain screen systems and particularly a system that Monarch would provide with those brackets and vertical profiles, it’s deflection joints that is a major issue of concern to always be looking how to accommodate floor movement. 

I mean there’s so many details that they have to get on paper. They don’t know the systems aren’t necessarily specified out while they’re making architectural drawings and the system that you’re bringing in, may change from what they originally thought was going to be installed. So therefore, how are you supposed to know what the details are, if you don’t even know what the system is?

What would you say is your main focus as a structural engineer, I know you do a lot on the exterior cladding, the building envelope, but what would you tell someone what your main focus is?

Alright so me personally I’m the manager of one of the panel engineering groups. Typically what I focus on is composite panels, like when I say that I mean like ACM metal panels, flexible panels there. And then their panel systems for attachment to a substructure like Z framing, hat framing, Monarch’s system of the brackets and vertical profiles, those types of framings. And then along with that comes fiber cementitious panels. I do the perforated panel modeling. And then any other stone, a rigid panel, phenolic panel, which is basically compressed, pressed paper or wood fibers essentially. So I really focus on those rigid panels, and then their framing system to the structure. Everything I do I start at the exterior of the building and make my way to either the stud framing, the concrete structure of the CMU wall. I really don’t have any design of those areas. So that’s not my area of expertise. I really stopped from the exterior wall really of the structure. 

And then as an engineer what I’m focused on is making sure that the components that I’m designing meet code. That’s really what everything is; just make sure they meet code [laughter]. So performing calculations, determining the wind loads, the weight of the panel, snow loads, all the loads that are derived from codes, ASC7 is typically where we derive most of our codes from. Determining how that transfers through the system, and making sure every component in that system meets codes per stress, shears, and fastener pull-outs. Just making sure every part of that system is going to be meeting code; it will be safe per code standards. 

If I’m designing a building with exterior cladding what are the structural priorities I want to keep in mind? So you’ve hit on a few of those so could you reiterate those again?

Okay so the priority structural priorities for when designing rain screen systems or whatnot. So first off it’s making sure that the wind loads are calculated properly. So we have wind loads, weight of the system doesn’t typically control unless it’s like a curtain wall system but for rain screen systems unless it’s a heavy, heavy panel system, like a 2-inch thick, limestone those little light metal panels aren’t really going to control for weight. You’re still accounting for that but those usually won’t be the design concerns. 

Seismic, seismic conditions, seismic category C or D which you’ll usually see those more towards the coast, especially in the California, Oregon, and Washington areas. Making sure that you can accommodate the lateral movement, as well as the vertical movement, for those systems from a seismic perspective, allowing for vertical movement, for thermal, and for the floor movement joints. Making sure the system is allowed to move and doesn’t tie everything together where you’re going to have issues like we had discussed earlier.

So making sure that, again, meets code and that would mean deflections of members, deflections of panels. That will be specified in the project specifications, but also per IDC international building codes, they also direct us on what deflection limits typically should be, depending on what kind of panel system we have, rather they be rigid or flexible. And that’s the majority of what we’re looking for when we’re trying this.

So when you’re at say, bidding a job or don’t have an engineering background, what items you should be looking for more so. What your substrate is, again if we have hollow block CMU stud or blank gauge 18 gauge studs, well you got to keep in the back of your mind you’re going to have a lot closer clip spacing then if you’re installing to concrete, or thicker like a 12 gauge or 16 gauge stud, assuming that the system fails due to the fastener. But then again it’s just checking through, making sure every component meets its individual code. Like all the steel components meet the cold form steel manual, or the structural steel manual, AISC in particular. The aluminum components meet ABM standards, aluminum design manual standards for stresses and deflections. 

I guess that’s another thing for architects, going back to the architects, is making sure there’s an allotment for those seismic conditions. That’s another one we see is, we are having all this lateral force and movement. I mean that, we’re going to have issues with joints, I mean if our panels are only allowed to rack, say half an inch, but the joints only a quarter-inch in architecturals, well that joints going to need to increase otherwise you’re going to have panel systems hitting one another and possibly crushing or cracking. So that’s another one from a previous question about, not necessarily what architects get wrong but some items that we see and need to identify and correct.

Why do companies in the commercial construction industry choose to engage a structural engineering firm, are they required to? Do they make the conscious decision to do it? 

Okay so, two reasons. Sometimes project specifications do require stamping of shop drawings. They require stamping and seal the shop drawings, stamp and seal of the calculations. So it can be included in the project specifications, why you’ll need engineering calculations or support or guidance. 

Other than that too is, you can make sure that the product that you’re providing is safe, and installed per code, so it’s as safe as code provides. So if you were to have a wind event that’s higher than what was provided by code, but it was designed per code, well at least you’re covering yourself because you did the due diligence of providing engineering calculations that confirm that this system should be able to handle typical code conditions. So it’s helping protect yourself as well, when it comes to if there’s a failure, if you don’t have engineering versus where you have engineering. The failure shouldn’t occur nearly as much, if at all, when you have engineering, unless again you have an event that’s outside of what code calls for because we can’t design for every single wind event right? I mean that, you’d be over designing everything and everyone already thinks we do that.

Speaking of using you as a structural engineer, what states do you currently have stamps in?

So Rice Engineering has stamps in all 50 states. I believe all of Canada, there might be one province I’m missing out. Mexico I believe, possibly Puerto Rico in the Virgin Islands. Basically anywhere in the States we can do, and then most of Canada. 

What are the top three advantages to working with a structural engineering firm?

Yeah so again it’s just to ensure building codes are met. Ensure your project that all building codes are met. We can also, I know working with Monarch, try to help optimize systems. So we can look at systems, you’ll send over an L profile or whatnot. Well can I just make this portion slightly thicker and cut down material on this portion of the component? And then maybe we can optimize how the system performs without increasing material everywhere and therefore cost. So we can help with optimization of any component or rain screen system. 

And not just optimizations of the systems themselves, but when we get a project, we can look at how it’s being installed, and maybe there’s a different way where they’re not accounting for lateral movement, or maybe there’s just so many parts and pieces, we don’t really need to meet codes or whatnot. We have come into that, again. So maybe we can remove some framing or space clip systems or horizontal railings and help further, try to save money that way.  So we can actually look at your details or see, okay this is just not going to work here you’re not preventing this panel to basically not even stay on the building for how this is installed currently. So we can help direct on ways to actually secure the system. 

Yeah and then also items that are not constructible. So there might be times where there’s really no way you can install this fastener how it’s drawn. Okay well now we have to think of how we can actually install this system, because I mean what’s the point providing engineering on something that you can’t actually install? So then actually identifying what’s constructible and what’s not is also a service that engineering will be providing in their engineering calculation package. 

I am curious to know what you would say people are most surprised about when doing business with a structural engineering firm? I’m learning so much talking to you all the time Rhett, and so, what would you say the biggest surprise people get from working with you?

So I’m going to take it back to a previous answer and kind of tie it in, like with the cracked concrete anchors. 20 years ago, I’ve been in this business for 20 years [laugher], this is what I’ll hear, “I’ve been in this business for 20 years, we never had to do this before, what’s changed?” Well codes don’t always, but tend to, get more stringent [laughter]. So something that worked ten years ago, doesn’t work now. And that’s usually due to, okay we have more empirical data from say, we have more wind speed data, okay hurricanes are becoming more prevalent in this area. Do the wind speeds need to be upped? And that’s always defined by the boards on whoever provides the codes, like the ACI concrete, or that ASCE, it seems like every time we have an update to that code, we have different wind speeds that we’re designing towards. 

So that is the biggest thing you’ll see as a surprise. We’re not trying to make anything more costly, just that to meet code they’re always finding new information to make buildings ultimately safer.

And then there are also those clients that are working between states. How varied those codes could be from say, Minnesota compared to Florida especially. So if they do all their work in Minnesota and they’re going to start to do installation jobs in Florida, that wind speed is totally different, [laughter] when it comes to that. ASE710 for typical building we’re designing for, 115 mile per hour winds in Minnesota. Or if we were in Miami County, we’re looking at 170 plus mile an hour winds. It knows if you can get with us early on and we can inform you before you underbid a project, hopefully, and you actually account for having to change a lot of spacing or system thicknesses, like gauge thicknesses, on framing, and all that. So I’d say that is a major surprise too is just how surprised people are between codes between the states.

And then also reviewing boards too as there’s some stringent reviewing boards that review calcs and shop drawings.

Typically you’ll see that with like a hospital or something especially out in California where they have a lot of seismic, and those we’ll see a lot more reviewing bodies, even certain towns or counties, like I mentioned Miami County. Miami County and Broward County in Florida have much higher wind speeds than just Tampa Bay on the other side of the state. So local codes, county or city codes can also be different. I know LA for one requires a Coaler report which is basically an ESR report. It basically is just a verified testing of each fastener that you can use the job. So you have to have true test reports, and that are stamped and certified by the reviewing board to use in that county. So we will direct you to which fasteners to use that can meet those conditions. 

How have you personally seen the U.S. cladding market change while you’ve been involved in it?

I’ll go with rain screen panel systems first. It used to be everything was just a sealed joint. So we’re installing these metal panels, you have like this ⅝ inch joint in between for an ACM or just a typical metal plate panel. And so you’d only have one layer protection of water infiltration. Well now we have all these rain screen ACM systems that have like a little ACM insert. And they will allow, you’ll stop basically 90% of the water, let’s say 7% of that moisture gets in, but we’re allowing for that moisture to get in. There’s like two layered systems for water infiltration. Those are also tougher to design [laughter]. So it’s getting those but you’re more worried about water infiltration, and you don’t want just a one-step to prevent anything right? We want some redundancy in design, so that we can prevent any water infiltration issues or actual failures. 

Another one that we’ve seen coming across here a lot more is a push to going green. So what I mean by that is more thermal performances, more companies want to see thermal modeling of systems. And again, a lot of times I’ve seen a lot of these rain screen systems that are clip and rail, because that’s less penetration through the insulation layer. Your bracket systems can be every 44 inches where before we’re fastening through every 16 or something like that. Going green is a major item that we see coming through and it’s just driving how we’re doing all these systems. 

Another one is we’re seeing a lot of European designs and components coming through and what I mean by that is a lot of glass fiber reinforced concrete panels, phenolic panels, and stone panels. Those are coming more and more and more prevalent. Those companies that are over overseas are starting to get in the US markets again, and architects are really pushing to have those types of components on their cladding. So we’re seeing a lot that will require some kind of sub framing system that ties into quick installations. And quick installation would be a componentized, sub framing system. So you have these brackets they can [install] on the wall, they can throw up the rail. It has adjustability, you don’t have to shim out, before it used to be everything was Z’s and hats.

So you’d have a solid Z going across this building and you’d have to shim out maybe every other fastener depending on how off whack, off plumb the wall is. Well now with systems, like what Monarch has, where you can have adjustability in the field, that’s becoming a big market whenever we’re talking with contractors. They want that adjustability; you have to have that adjustability. 

Where do you see exterior cladding in the US in five or ten years from now? I mean you’ve kind of described where you’ve seen it come to, what do you think are the next steps logically?

I was talking with a few other engineers that have been around here for 25, 30 years, that have even more experience but in pre-engineered systems. So you can just go out and pick this system and we already know that it has testing to back it up. And engineering calcs ran on it for like you say, well if a lot more E330 testing on systems so you can just bring them by the system and already engineered you have to need to worry about it, you can spec it out as an architect, throw up on the wall, we’re good. Just make sure that the wind loads are still within that realm, which speeds up the whole engineering calculation process, and is easier for architects and contractors to determine what system to use. 

I’ve seen something like a lightweight stone panel, where they do a panel veneer. Which is maybe a quarter inch thick, and it’s like granite or limestone or whatever kind of stone we want to use here. And they do a honeycomb backer, like this aluminum honeycomb backer, and that’ll be like ¾ of an inch. So if the architect wants an inch deep panel, well now instead of an inch thick of heavy stone, you’re now a quarter of the way to that. I can see that becoming a major push in the future. Hopefully, it’s a lot nicer to engineer when it comes to those actual bracket systems. 

Obviously everything is trying to, everything’s going to get more expensive right? Materials are more expensive than that so we have to find ways to optimize and maximize the materials and the spacing of systems. So that’s a never-ending push but might as well mention it nonetheless.

I already mentioned sub framing system adjustability. Again that’s going to keep carrying out.

Leed requirements, so basically that energy efficiency again, they may be wanting more recycled content in panel systems. So for instance, like those glass fiber reinforced panels, if they need more recycled aggregates to use in those panels for instance. I could see that being more of an issue or concern going forward. Again that also helps with trying to cut prices on everything that’s increasing. 

Possibly, along with that Leed requirement, more fiberglass may be involved. Like fiberglass thermal clips or something of that nature. Just because then you don’t have as much thermal bridging between your sub framing system and going back into your structure. The only thermal transfer or the most thermal transfer then would only be through the fastener penetration that would bridge. I can see that becoming a larger portion of the market. 

Another big one too is, when I first started, project schedules from start to install. Okay I mean you may have a year, year-and-a-half of planning and actual manufacturing. I’m only seeing the project schedules getting more and more and more condensed [laughter]. And now it’s everything is, okay we can get that done in eight months, six months, engineering needs to be done in two or three weeks [laughter]. The project schedules, which again, is really going to push that sub framing system adjustability and the pre-engineered systems.  

Brandon: It’s interesting you mentioned honeycomb, I don’t know if I’ve told you Rhett, but we brought to market at the end of last year, a new honeycomb deform nut rail and clip system.

Rhett: Oh yeah?

Brandon: Yeah so if you do have any of those honeycomb jobs come along, we now have some things on our website and everything. And we did a really fabulous couple jobs in Los Angeles already or Santa Clara. And so it’s another exciting product that Monarch’s brought to market.

Rhett: Perfect, yeah, being able to cut that weight down, especially when you’re trying to provide also your own adjustable sub framing system that only helps even further so we don’t need to rely on having two or three dead load clips per profile, helps out even more.

Monarch’s Honeycomb Sandwich Panel Installation System
for progressively installing veneered honeycomb panels

Another item too would be that we could see going forward is, NFPA220 more enforced. So that’s the fire rating of panel systems, I don’t know if you recall but in the news a couple years ago there was a building in, I want to say London, where we had the ACM panel fire. And there’s going to be more fire rated composite panels for sure. But also, it seems like there’ll probably be more testing on a lot of components when it comes to this. You’re only going to see more components being tested for this. And there needs to be. 

We’ll see in the cladding especially, is okay was there a horizontal break at every floor? Or was that fire allowed to just chimney effect which is what it seems like they made a chimney effect where, there was no horizontal break between the vertical panels. So that fire could just spread all through the exterior of the building straight through the panels, and then it creates a chimney effect. Well is there going to be more requirements where we have to have a break so we have to have some kind of insert at every floor line, so this doesn’t occur? So we stop a fire at that floor, prevent the quick spread of that. 

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