Explore the intricacies of measuring units in various construction processes. This article breaks down the different units of measure used for different materials and labor involved in construction projects, from general conditions to carpeting requirements.
Key Insights
- The unit of measure used in construction varies by material and labor type, for example, general conditions are measured by duration, site work and grading usually use square feet or acres, and reinforcing steel could be measured in linear feet or by the ton on larger projects.
- Understanding the units of measure used by suppliers for materials and subcontractors for labor is essential in determining the cost of labor and material based on their units of measure. This includes understanding that some materials are sold differently than they are used, leading to potential waste.
- Each type of material or labor has its own unique measuring units. For instance, wood framing uses board feet, structural steel is measured in tons, roofing tile is based on squares, and plaster is priced out by the square yard.
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So let's talk a little bit more about units of measure. And the question might come up: how do you know what to measure something by? It just comes with practice, and with a little bit of research to find out exactly how things are being priced out. But the first step, as mentioned earlier, is to find out from your suppliers how the material is sold.
Then also find out from your subcontractors, if you don't already know, how the labor is going to be performed. Because the bottom line is, you're going to look at the cost of labor and the cost of material based on their units of measure. So here we have general conditions.
General conditions are measured by months or weeks—it's a duration in time. So whatever it costs for your company to operate that project per month, and then you know it's going to be a six-month project or a 12-month project, that’s how you determine your total general conditions cost. Remember, general conditions are similar to—or the same as—GCs.
Site work and grading typically use square feet, acres, or cubic yards. Reinforcing steel could use one or the other as a unit of measure. It could be either linear feet, or it could be priced by the ton on larger projects.
Understand that when it's priced by the ton, it’s going to say a ton of what. Well, it might be a ton of number five rebar or number four rebar. So more information might be required, but typically that’s how your reinforcing steel would be priced. Concrete footings—again, that’s a volume calculation—so that’s going to give you cubic yards.
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Concrete slab is by the square foot. We touched on that as well. Your masonry.
Masonry walls have different thicknesses. They go deep into the structure. It could be six inches wide, it could be 12 inches wide.
That doesn’t matter, because in masonry, it's going to be a square foot cost per square foot of surface area, and that has to be factored in with the type of masonry being used. Is it six inches wide? Is it nine or 12 inches wide? But typically, that’s how your measurements are calculated with masonry—by square foot. Wood framing and lumber use board feet as a measurement.
That’s 12 inches wide by one foot long by one inch thick. That is considered one board foot. Most of the stores—most of the supply houses you go to—will sell you the wood differently, and it’s a little bit easier to work with.
“I’ll take 20 two-by-fours” or “I’ll take two-by-sixes, ” except they need a thousand feet of those. They can be priced that way, or they can be priced by the board foot. The board foot itself can actually be a preliminary number overall based on square footage.
It will be approximately a certain number of board feet. This will not be part of the estimate, but it’s important to understand or recognize BF as meaning board feet, should you ever come across it. Let's talk about plywood.
It’s measured by the square foot, but keep in mind that when you purchase it, you have to purchase it by the sheet. There are a lot of products like that, so there could be a lot of waste associated with it. If you're going to price it out by the sheet, it’s still going to be a total of four by eight—or it could be, you know, four by ten or even four by twelve, if you can find it that large.
If you use one unit to measure square feet, keep in mind that you might have to find out how it’s purchased, and you may have to buy additional feet. In other words, it’s going to generate perhaps a lot of waste that you hadn’t anticipated. We'll talk a little bit more about the waste factor as we get into the class, but it's important that you get compensated for every square foot or linear foot of material that might be out there—whether or not it’s all installed.
Structural steel—this is the real heavy stuff. This is what we refer to as the structural element of a building. It is measured in tons, and that’s tons per foot. When you have certain size I-beams, those I-beams are going to range in length, but the tons per foot doesn’t change unless you get into a larger size altogether.
So TN for tons is not uncommon. It is typical for structural steel measurement. Sheet metal is by the square foot, but then again, understand that a lot has to do with the gauge of material, which will drive the price up.
It’s all measured by the square foot, but the price of the different types of sheet metals and thicknesses makes all the difference. Roofing tile is a little bit unusual, which is why I included it as well. Roofing tile is based on squares—not a square foot, not a square yard, but a square of roofing material.
So technically, you have a 10 × 10 area as a square. But if you think about it, roofing tiles overlap each other. Well, what about all the overlap? How is that factored in? Well, technically, the roofing tile for a square already factors in the tile that’s going to get lapped over the next layer or the next row. So theoretically, roofing tile covers considerably more square feet than just a 10 × 10 area.
Doors and windows—these are priced out, and labor is performed, based on “each” or a count. Plaster is another unique one. It’s priced out by the square yard—and if you’re going to ask me how we came up with square yards, I honestly don’t know.
It’s been around forever. It’s nine square feet of surface area for your plaster. Although the plaster itself is actually purchased in bulk—by certain size sacks that mix with water—or it’s going to be priced per cubic yard as well.
So keep in mind that plaster by the square yard is synonymous with—or very similar to—stucco, even gunite, Venetian plaster, or whatever it may be. It’s a different measurement in thickness for each one of them, but at the same time, it’s still measured by square yards. Metal studs are measured by the linear foot. But keep in mind that within a metal stud itself, there are many other factors to consider such as the gauge of the stud, the width of the stud, whether it's structural, considered structural, or galvanized, and so on.
All studs—for metal framing, for example—are measured in linear feet. Drywall is measured in square feet, and similar to plywood, note that you could have a total square footage, but when you purchase the material, are you going to purchase it in four-by-eight sheets, four-by-ten, or four-by-twelve sheets? Each one of them has different factors regarding how much waste will be involved.
So in this particular case, you’re only going to have exact quantities of surface area for your labor to install drywall—but you’re going to have to purchase considerably more in square feet. You might look at how many sheets you need to purchase, which will tell you the total square footage. Floor tile is typically measured by the square foot. Carpet—there are two types of carpet measurements that we may come across.
