Calculate the size and spacing of floor joists needed for supporting floors in residential or commercial buildings.
| Span (ft) | Joist Size (inches) | Spacing (inches) | Max Span (ft-in) | Number of Joists |
|---|---|---|---|---|
| 12 | 2 x 6 | 16 | 10-3 | 10 |
| 14 | 2 x 8 | 16 | 12-6 | 12 |
| 16 | 2 x 10 | 16 | 15-0 | 14 |
| 18 | 2 x 12 | 16 | 17-4 | 16 |
| 20 | 2 x 14 | 16 | 19-6 | 18 |
| 22 | 2 x 16 | 16 | 21-8 | 20 |
| 24 | 2 x 16 | 12 | 23-10 | 24 |
| 26 | 2 x 16 | 12 | 26-0 | 26 |
| 28 | 2 x 16 | 12 | 28-0 | 28 |
| 30 | 2 x 18 | 12 | 30-0 | 30 |
A floor has a span of 20 feet, and you plan to place joists every 16 inches. How many joists are needed for the entire floor?
Solution: Convert the span to inches (20 x 12 = 240 inches). Divide by the spacing (240 ÷ 16 = 15) and add 1 extra joist. Total joists needed = 16.
You have a floor with a span of 18 feet. Joists are spaced at 12 inches apart. How many joists are needed for the floor?
Solution: Convert the span to inches (18 x 12 = 216 inches). Divide by the spacing (216 ÷ 12 = 18) and add 1 extra joist. Total joists needed = 19.
If a joist is 2 inches wide and spaced 16 inches apart, what is the space between each joist?
Solution: Subtract the joist width from the spacing (16 - 2 = 14 inches). The space between each joist is 14 inches.
A floor requires joists for a span of 24 feet, with joists spaced every 24 inches. How many joists are needed?
Solution: Convert the span to inches (24 x 12 = 288 inches). Divide by the spacing (288 ÷ 24 = 12) and add 1 extra joist. Total joists needed = 13.
A contractor needs to build a floor with a span of 14 feet using 2x6 joists. If the joists are spaced every 16 inches, how many joists are required?
Solution: Convert the span to inches (14 x 12 = 168 inches). Divide by the spacing (168 ÷ 16 = 10.5) and round up, then add 1. Total joists needed = 12.
You need to space joists every 12 inches for a 10-foot span. How many joists will be needed?
Solution: Convert the span to inches (10 x 12 = 120 inches). Divide by the spacing (120 ÷ 12 = 10) and add 1 extra joist. Total joists needed = 11.
A deck with a 30-foot span requires joists spaced every 24 inches. How many joists are necessary?
Solution: Convert the span to inches (30 x 12 = 360 inches). Divide by the spacing (360 ÷ 24 = 15) and add 1 extra joist. Total joists needed = 16.
If each joist is 1.5 inches wide, how much total width will 14 joists take up in inches?
Solution: Multiply the number of joists by the width of each joist (14 x 1.5 = 21 inches). Total width = 21 inches.
For a span of 22 feet, joists are spaced every 16 inches. How many joists are required?
Solution: Convert the span to inches (22 x 12 = 264 inches). Divide by the spacing (264 ÷ 16 = 16.5) and round up, then add 1. Total joists needed = 18.
A floor has a span of 26 feet and requires joists spaced every 12 inches. How many joists will be needed?
Solution: Convert the span to inches (26 x 12 = 312 inches). Divide by the spacing (312 ÷ 12 = 26) and add 1 extra joist. Total joists needed = 27.
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