Floor Joists Span

Reference data and engineering information about floor joists span for building and construction applications.

floorjoistsspan

Overview

Engineering reference data for Floor Joists Span in building construction.

Key Formulas

U-value

$U = \frac{1}{R_{total}}$

Overall heat transfer coefficient.

Heat Loss

$Q = U A \Delta T$

Heat transfer through building envelope.

Variables

Symbol	Description	Unit
$U$	U-value	W/(m²·K)
$A$	Area	m²
$\Delta T$	Temperature difference	K

Maximum Floor Joist Spans

The following tables provide maximum floor joist spans for No. 1 and No. 2 Grade Douglas fir lumber under specified live loads. Dead load is assumed to be 10 lbs/ft².

11 rows

Maximum Floor Joist Span, Live Load 30 lbs/ft² (1436 N/m²)
Nominal Size(in)	Joist Spacing (C to C)(in)	Selected Structural Grade(ft-in)	No. 1 Grade(ft-in)	No. 2 Grade(ft-in)
2 x 6	12	12' - 6"	12' - 0"	11' - 10"
2 x 6	16	11' - 4"	10' - 11"	10' - 9"
2 x 6	24	9' - 11"	9' - 7"	9' - 1"
2 x 8	12	16' - 6"	15' - 10"	15' - 7"
2 x 8	16	15' - 0"	14' - 5"	14' - 1"
2 x 8	24	13' - 1"	12' - 4"	11' - 6"
2 x 10	12	21' - 0"	20' - 3"	19' - 10"
2 x 10	16	19' - 1"	18' - 5"	17' - 2"
2 x 12	12	25' - 7"	24' - 8"	23' - 0"
2 x 12	16	23' - 3"	21' - 4"	19' - 11"
2 x 12	24	20' - 3"	17' - 5"	16' - 3"

Source: engineeringtoolbox.com

12 rows

Maximum Floor Joist Span, Live Load 60 lbs/ft² (2873 N/m²)
Nominal Size(in)	Joist Spacing (C to C)(in)	Selected Structural Grade(ft-in)	No. 1 Grade(ft-in)	No. 2 Grade(ft-in)
2 x 8	12	13' - 1"	12' - 7"	12' - 4"
2 x 8	16	11' - 11"	11' - 5"	10' - 8"
2 x 8	24	10' - 5"	9' - 4"	8' - 8"
2 x 10	12	16' - 8"	16' - 1"	15' - 0"
2 x 10	16	15' - 2"	13' - 11"	13' - 0"
2 x 10	24	13' - 3"	11' - 4"	10' - 7"
2 x 12	12	20' - 3"	18' - 7"	17' - 5"
2 x 12	16	18' - 5"	16' - 1"	15' - 1"
2 x 12	24	15' - 10"	13' - 2"	12' - 4"
2 x 14	12	23' - 11"	20' - 10"	19' - 5"
2 x 14	16	21' - 8"	18' - 0"	16' - 10"
2 x 14	24	17' - 9"	14' - 8"	13' - 9"

Source: engineeringtoolbox.com

Unit Conversions

For reference, the following unit conversions are commonly used in structural engineering:

1 psf (lbf/ft²) = 47.88 N/m²
1 ft = 0.3048 m
1 in = 25.4 mm

References

Original Source

Source: engineeringtoolbox.com