Lexi: Welcome back to another episode of Metal Minutes by Cornerstone Building Brands. My name is Lexi, and I’ll be your host. With me today I have Jacquie Baker. She is the estimating manager at Star Building Systems. Hi Jacquie.
Jacquie: Hi, how are you?
Lexi: Doing well and yourself?
Jacquie: Well, thank you.
Lexi: Okay, so today’s topic will be what to know when building and engineering mezzanines in your metal buildings. I think the first thing to discuss is what is a mezzanine and what does that mean?
Jacquie: Yeah, absolutely. Mezzanines are your second floor, your third floor. It’s not the floor sitting on the ground. It’s something where we’re attaching it partway up on columns.
Lexi: Okay. Pretty straightforward. Let’s start off with what we need to know as we’re approaching building a mezzanine. So what are the most important things to consider?
Jacquie: Well, we always start with loads, right? We can’t go anywhere or do anything with the building, unless we… We don’t know about our loads. The two main ones for our mezzanines you want to be concerned with are your dead load and your live load and something to remember, and because it’s really named the same thing, your mezzanine live load is different from your roof live load. And with these loads, of course, the bigger the load, the greater the load, the more impact to the cost of the mezzanine. And so you always want to make sure that you’re using the correct loads.
Lexi: So you mentioned a few different kinds of loads. Let’s talk about the first one you mentioned, what is a dead load?
Jacquie: Yeah, this is anything that’s not going to move. It’s attached to the floor in the sense of your concrete or your plywood, your steel deck. Like I said, think of it as being the self weight of the permanent decking. We also internally take care of the dead load for the beams and joists, but that’s not something you have to worry about because that’s not something you know until it’s designed.
Jacquie: So we just need to know for the dead load, what are you putting on there? So if you’re putting a plywood deck on there, we’re looking at a pound per square inch for every quarter inch of thickness, which is a little confusing. But if you have a one inch plywood deck, then your dead load is going to be four pounds. And so that’s an idea for plywood.
Jacquie: We can also look at concrete decks, typically around four inches. If you’re using normal weight concrete, you’re going to have about 50 pounds of dead load. So you can see that there’s a pretty big difference between using plywood or concrete. And so that’s why we say make sure you know how thick your concrete is so that we know that we have the right weights for your concrete.
Lexi: Okay. So the dead loads are basically the things that are pretty permanent to the structure. You’re not going to be able to change those very easily.
Jacquie: Right, right. With these weights being so different, if you’re middle of the US, your loads on your building are really sunshine loads or wind loads, your dead weight of your mezzanine isn’t going to come into play as much as if you were in a high seismic area. Areas like surprisingly Charleston, South Carolina, or you’re near the New Madrid fault in Missouri, or you’re in Alaska, Hawaii, California, anywhere there on the ring of fire, your high seismic areas. These weights are going to play a big role because when you have your building, it’s like having an eraser on top of a pencil. And the bigger that eraser is, if you move it back and forth, that pencil wants to throw itself back and forth in your hand. So when you’re in high seismic and your building’s moving, that heavier deck is going to push your building back and forth quite easily.
Jacquie: And so when we’re in an area that’s high seismic, if you can use a plywood deck, we can take an exception in the code that would allow us to use ordinary moment frames. The reason that this is so significant is that if we have to use a concrete deck, we’re going to end up having to use special moment frames and they are special just like they sound. And they cost three times more, if not even a little more than that, than your typical ordinary moment frames. And so being able to understand what your dead loads are and being able to possibly use that plywood exception if you’re in those areas of high seismic will really make a big savings on your project.
Lexi: Okay. So the dead loads or some of the things that go into calculating the dead loads, that could change based on your geographic location?
Jacquie: Well, the weight will still be the same, but how your building reacts to that weight is going to be different.
Lexi: Interesting. All right. So you had also mentioned live loads that go into the engineering of building a mezzanine. So let’s discuss what live loads are.
Jacquie: Yeah. So these live loads, you can think about it, it’s something moving. It’s alive, and obviously it’s not all alive, but things that can move. So people, furniture, filing cabinets, storage racks. In some cases where we have a grain storage building or somewhere where they’re manufacturing and moving grain around, they might even have grain stacked on these mezzanines. They’re not permanent. They can be moved around and they may not necessarily always be in the same place at the same time. If you think about your office in 2020, I’m sure it looks very different now than it did a year ago. Cubicles have been moved, people have been adjusted and a lot of those buildings are changing how they’re operating because how we operate these days. And so those are live loads.
Jacquie: The building code has a minimum for our live load requirements. So when you look into the building code, it’ll say for a light storage mezzanine, you’re looking at about 125 pounds per square foot. But if you have just an office, the minimum is 50 pounds per square foot. So it’s a big difference. It’s about 75 pounds per square foot, whether you’re building a storage mezzanine or an office.
Jacquie: This is important again, because our beams supporting this are obviously going to get bigger with those bigger loads. So you have to make sure that you know what you’re using. For both dead load and live load, one thing that’s really fantastic is no matter which Cornerstone software you’re using, we have a cheat sheet in there for you.
Jacquie: So if you click on the help button at the bottom of the tab where you’re inputting your mezzanine, you’ll get a cheat sheet that pops up and it’ll give you your averages for your dead loads. And then it also gives a description of the different types of live loads. Of course, it doesn’t encompass all. I don’t think the code could encompass all live loads if it wanted to, but it gives you a very good range so that you have an idea of what you want to use.
Lexi: Okay. That’s some great information. So my next question is how do you even start to configure something like live loads? When it’s something that’s so easily moved or changed, how do you estimate what those are?
Jacquie: Yeah. When you’re looking at the live loads, you just know what the general use of your building is. Is it going to be a stage or is it going to be a classroom? So you know what you’re going to be using your second floor for typically. So the entire floor will be designed for that load. So even if you have a desk two feet from the wall, and then you have nothing for another 15 feet, and then you put another desk between that desk and the next 15 foot section, it’s still being designed if it’s an office for that 50 pounds per square foot, because maybe you move the desk over, maybe you readjust your floor. And so every part of your floor will be designed for that.
Lexi: Okay. That makes sense. So we’ve talked about the dead loads and we’ve talked about the live loads. What else do we have to consider when calculating loads for mezzanines?
Jacquie: So the next one is our partition load. This one’s a subset of a live load, but we keep it in its own category because the code gets a little crazy with what it wants you to do with these partition loads. So the partition loads account for any walls or any partitions, anything that’s going to be sitting on the mezzanine that you would think of as a partition, like a wall. Something that’s separating two areas. The reason we, like I said, keep it in their own category is because of the code and the code applies it differently, depending on the use of your mezzanine, which gives you your live load.
Jacquie: So when we’re talking about anything that’s below 80 PSF, that’s going to be your laboratories, your walkways, your office use, your classrooms. Anything like that, you’re still going to have to put in a 15 PSF partition load.
Jacquie: And the reason is, is that the code thinks, Well, maybe right now, you haven’t put a partition in there.” But I don’t know how many of you guys have dealt with this, but on our floor, they started building offices and started putting up walls were walls weren’t before. And so as we expanded, we built more offices. And so our partition could go there. So we do have to apply that 15 pounds per square foot load if we’re using 80 pounds per square foot or less. And that 80 is our magic number.
Jacquie: If your live load is then between 81 and 100 pounds per square foot and you know that you’re going to install walls, you have to put your 15 pounds per square foot partition in, and this gets full of numbers. And there’s one more set of numbers that I’ll give you.
Jacquie: But at the end of the day, the best thing to do is to call one of your representatives, call your district sales managers, call your estimators. We are more than willing to help you because we’re nerds and we like this kind of thing. And most people don’t want to sit there and stare at a code all day long, right?
Jacquie: So the last one is, is if your mezzanine is more than a hundred pounds per square foot, you don’t need to worry about your 15. So your hundred pounds per square foot, don’t have to worry about your 15. We’re already considering that if you have light storage or heavy storage, we can almost guarantee that what you’re storing weighs more than what a partition wall is going to be anyway. And so then we can completely ignore it.
Lexi: Okay. So it sounds like the partition loads are the loads that account for any future alterations to the building.
Lexi: So three loads that we have to take into consideration so far, what else?
Jacquie: And then we have collateral loads. And this one also, this one is variable. We have these live loads and we tell you, “This is your range.” And we have the dead loads and we say, “This is what it has to be based on the thickness.” Your collateral loads start to get a little variable, because these are for things like your lighting, your HVAC, your sprinkler system. You’re not setting it on top of the mezzanine because nobody’s going to run HVAC ducting across the floor to trip over, but you are attaching it underneath because the first floor is going to need lights. It’s going to need to be heated or cooled typically. You’re going to need those sprinkler systems. Maybe you’re putting in a drop ceiling, because nobody wants to look at the underside of their mezzanine.
Jacquie: And so these collateral loads will be given to us by our builder or whoever we’re working with so that we can apply those into the buildings. There are some typical general numbers for them, but as we get to the point that we’re ordering this, we need to know for sure. And that will come. The HVAC company that’s supplying your HVAC will tell you, “This is how many pounds per square foot you need to account for for my equipment.” Or the lighting guy is going to say, “My lighting here is only going to be a pound per square foot.” So you say, “Okay, write that down, tally them up and then throw them into the software for us.”
Lexi: Okay. So the things that go into calculating collateral loads aren’t necessarily sitting on the floor, but the supporting beams of the buildings still have to support the weight of them. Correct?
Lexi: Okay. That’s pretty straightforward. Then what else is important to know about building mezzanines?
Jacquie: Well, I think one thing is nobody wants to walk into a mezzanine, right? You don’t want to come through your three foot by seven foot door and smack your head into a mezzanine. So the other thing is, what kind of space do you have in your building to put this mezzanine in? Let’s say, we’re talking about a typical mezzanine and you have four inches of concrete on there. You’ve got an inch and a half of deck. You’ve got your joists, they have a two and a half joist seat. Then you’ve got the depth of your beam. So all of these little things are adding up. It might be four inches here, inch and a half there, two and a half inches. Maybe you get to your beams and you have 12 inches or you have 30 inches. How much room do you have to put this into your building where people aren’t, or equipment aren’t going to be interrupted by the mezzanine in the building?
Jacquie: And so that’s one thing we always need to think about is what is your headroom underneath the mezzanine and what kind of headroom do you need for that mezzanine to the roof? So that again, you don’t bonk your head or you don’t run a truck into it or any kind of equipment. And so one thing just to consider is what’s the allowable space? So do we have a foot and a half to put this mezzanine in or do we have four foot? And also we can do restrictions differently in the sense that our joist, we may be able to go lower with the joist, or we may be able to go higher with the joist versus our beams, which are all support members of the mezzanine.
Jacquie: And again, this is another one of those. It kind of gets hairy, call us. That’s what we’re here for. We’ll get you where you need to go with that. But yeah, headroom is a big one. And that really depends on your spans. So if you have really long spans of a mezzanine where its attachment points are from end to end, then you’re going to get much deeper members. If you have a 40 foot span, your beam that you’re resting that mezzanine on is going to be much deeper than if you have a 20 foot span and you have a shallower beam. And so that also plays into your headroom and plays into your cost. The bigger your spans, the bigger the beams, the more you’re going to pay for it.
Lexi: All right. This has been great Jacquie. Is there anything else you feel our listeners would benefit from knowing about understanding mezzanine loads?
Jacquie: No. Just if they have any questions we’re here. That’s what we’re for.
Lexi: Great. Well, Jacquie, thank you so much for joining me today. This has been some great information about this topic.
Jacquie: Thank you. It was a pleasure to be here.
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