You're probably familiar with typical AEC new construction descriptions:
150,000 square feet!
11,500 yards of concrete!
3,300 tons of steel!
Don’t get me wrong, as AEC professionals, we love numbers. But what do those numbers actually mean? Do you ever feel like your brain is only impressed because it knows it’s expected to be impressed? Somewhere behind the part that’s going “Ooo, wow!” is a quieter part saying “Um…I don’t mean to be rude, but you really have no idea of what that actually means in real life...”
How big is 150,000 square feet? What does 11,500 yards of concrete even look like? And 3,300 tons is definitely a lot of weight, but still incomprehensible.
Ultimately, you have no scale of reference to put things in perspective. You just know that those are big numbers that are supposed to raise eyebrows.
So I’m here to help! Here are some basic rules of thumb for wrapping your head around the common building construction stats of square footage, volume of concrete, and tons of steel. The secret? Using “units” that you’re actually familiar with…
Personally, I like to imagine commercial building areas in units of rooms, apartments, houses, and Walmarts.
Yes, you heard me. Walmarts. We’ll get there in a minute
If you’re just dealing with a few hundred to a few thousand square feet, you probably already have a general feel for what that is.
100 - 250 square feet is about the range of a small to large bedroom to a living room.
500-1,000 square feet is a small to average one or two bedroom apartment.
1,500-2,500 square feet? Now we’re in the standard single family home range.
10,000 square feet? Getting bigger, about 5-7 houses squished together. But it’s starting to get a little harder to wrap your head around.
100,000 square feet? That’s a lot of houses.
So now we’re into the Walmart units. Most people are familiar with Walmarts and have a general feel for the size. And since I’ve spent most of my career working with Walmarts in new design or forensics, I also happen to know how they stack up in terms of rough square footage.
Walmart Neighborhood Market = 41,000 square feet
Typical Walmart Supercenter = 150,000 - 200,000 square feet
So, an office building that’s 32,000 square feet? Just slightly smaller than the Neighborhood Market where you grocery shop.
150,000 square feet? About the size of your local Walmart Supercenter. Way easier than trying to picture 100 houses together, right?
Yards of Concrete
Concrete volume is typically measured in “yards,” which is shorthand for “cubic yards,” or 3 ft x 3 ft x 3 ft blocks. Incidentally, a cubic yard ends up being somewhere between the size of a washer and a refrigerator.
Now, you could imagine concrete volume in terms of hundreds or thousands of washers and refrigerators, but there’s another unit you’re probably pretty familiar with: the concrete truck.
Everyone’s passed a standard concrete truck on the road or seen them on a job site. You have a pretty good idea of how big they are, and knowing how many trucks it took to pour the concrete at a building could be a useful frame of reference.
A standard concrete truck can hold 10 yards fully loaded, but often will have more around 8 yards.
So, if you’re told a project has 11,500 yards of concrete, you can do some quick math and realize that it took almost 1,500 trucks. Not insignificant. Just ask our special inspectors who have spent many a day and night monitoring concrete pours.
Tons of Steel
This one’s a little tougher. Assuming you’re mortal, your frame of reference on weight is probably limited to a bar and a few plates at the gym ‒ or if you’re like me, a few dumbbells (darn you, 15’s!).
But the concept of tons of steel can actually be broken down into something a little more tangible: flatbed trucks.
Per DOT regulations, trucks are limited to 80,000 lb total weight (including the self weight of the truck and trailer), which typically leaves about 46,000-48,000 lbs available for hauling.
So, imagine the last flatbed you saw going down the highway hauling steel wide flange beams or open web steel joists. Let’s say it’s conservatively hauling around 45,000 lbs, or 22.5 tons. So, when you hear about a job with 3,300 tons of steel, you can know that that’s closing in on 150 nearly-fully-loaded flatbed trucks.
A little more perspective? If you assume an open web steel joist is 48 ft long (about the length of an average flatbed trailer) and weighs 20 pounds per linear foot, that's 46 joists per truck!
Using these rules of thumb, the next time you read an AEC project description, you can at least have some tangible starting points for understanding square footage and common material quantities. Comprehensible “units” like “Walmarts,” “concrete trucks,” and “flatbed trucks” can help add some perspective to square footage, yards of concrete, and tons of steel so you can really grasp how projects stack up. With these new perspectives, next time, you won’t have to pretend to be impressed, you can actually be impressed (or maybe not, as the case may be…)