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Floor Joists Table

Common Floor Joists Materials - Span Table

These tables state that the given floor joists will not deflect more than 1/360th of the span as long as they are spaced no greater than 16 inches on center and the load will not exceed 40 pounds per square foot (PSF) live loading plus 10 PSF dead load. Span is defined as the greatest distance along the bottom of the joist between supporting beams or columns. If there is any doubt in your mind, contact a structural engineer.

If you are planning a house or a room addition, be sure to consult with a structural engineer. Have him or her specify the actual floor joist size. In addition, ask the engineer to verify that the wood joist delivered to the jobsite is, in fact, the correct material. Look on the side of the joist for the grade and species stamp!


Common Floor Joists Materials-Span Table

Lumber Species





Southern Yellow Pine #1 Grade
9'-11" 13'-1" 16'-9" 20'-4"
Southern Yellow Pine #2 Grade
9'-9" 12'-10" 16'-1" 18'-10"
West Coast Douglas Fir #1
9'-11" 13'-1" 16'-5" 19'-1"
West Coast Douglas Fir #2
9'-9" 12'-7" 15'-4" 17'-10"
Hemlock-Fir #1 Grade
9'-6" 12'-7" 16'-0" 18'-7"
Hemlock-Fir #2 Grade
9'-1" 12'-0" 15'-1" 17'-7"
Spruce/Pine/Fir Southern #1
8'-10" 11'-8" 14'-10" 17'-7"
Spruce/Pine/Fir Southern #2
8'-7" 11'-4" 14'-2" 16'-6"


3 Responses to Floor Joists Table

  1. I have built trusses for a patio cover and need to know if a 2x8 doubled up as a header on each side will carry the load? The 2x8s will be spanning 14'. The trusses I am sitting on them are a 20' span and are constructed from 2x8s as well on a 4/12 pitch. I will have 5 trusses sitting on the 2x8 headers spaced equally across the 14' span. The roof will be sheeted with R9 27 ga steel panels 2x8 headers will be #2prime Southern yellow pine

    • Mike, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  2. Over the winter my patio heaved from the frost and the deck on top of it is now back pitched. I ran level a line level on my 2"x10"x12' joists.
    My question is if i lower the front 1-1/2" how far will the back of my deck move. I did set up some boards and raised the front 1-1/2" and measured the back after i lowered the front and had hardly any movement. Thanks, Rick

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