Deck Floor Joist Spans - Part 1
Floor Joist Spans For Decks - 12" Joist Spacing
Part 2 - 16" & 24" Joist Spacing
If you are designing a deck, one of the calculations that you need is the size of the lumber required to span the distances between the deck supports or deck supports and wall.
The lumber span is from the inside of the support on one end to the inside of the support on the other end, as shown in Figure 1.
Additional information on decks with hot tubs or spas.
Deck floor joist span
There are seven factors that enter into choosing the correct lumber size.
Figure 2 - Deck floor joist spacing |
- Species of the lumber
- Grade of the species
- Length of the span
- Spacing between Joists (Figure 2)
- Dimensions of the lumber
- Pounds per square foot (psf) - live load
- Pounds per square foot (psf) - dead load
Check with your local building department to find out the psf requirement in your area.
Following are tables for the two most common required psf loads for 12 inch joist spacing. Both tables are based on the use of #2 grade lumber.
Table 1 is for 40 psf live load and 10 psf dead load.
Table 2 is for 60 psf live load and 10 psf dead load.
Table 1 12 inch Joist Spacing, 40 psf live load & 10 psf dead load - Grade #2 lumber |
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Length In Feet |
2 X 6 |
2 X 8 |
2 X 10 |
2 X 12 |
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8 |
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9 |
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10 |
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12 |
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14 |
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16 |
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Includes CAD software, deck plans and designs.
Table 2 12 inch Joist Spacing, 60 psf live load & 10 psf dead load - Grade #2 lumber |
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Length In Feet |
2 X 6 |
2 X 8 |
2 X 10 |
2 X 12 |
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8 |
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9 |
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10 |
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12 |
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14 |
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16 |
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Continued..... 16" & 24" Joist Spacing