Depth Of Floor Joists

Live load is weight of furniture wind snow and more.

Depth of floor joists.

You should check with your local building department for construction requirements in your area. While most residential construction uses 2x8 joists with 16 inch spacing there are many other factors you need to consider when determining the proper joist span length. E g for a span of 18 feet. Since the example house we are designing for is 12 feet wide we need to find in the floor joist span table a joist size and centering that can span 12 or wider.

The floor joist spacing is the distance between the centers of any two installed joists. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal residential construction. The rule of thumb for the depth of common joists is to take half span in feet. Joist span and spacing is set by your local building code.

No notching in the middle third of a joist. Maximum notch depth in the outer third of a joist is one sixth of the joist depth. 1 ft 0 3048 m. Half this is 9 add 2 which gives 11 inches for the depth.

For 23 32 and 3 4 inch panels joists should be 24 inches on center. The bulk of the floor s thickness comes from the joists which are the horizontal beams that carry the floor s weight. Builders can adjust their choice of lumber size and spacing depending on circumstances. To this number add 2 for the depth of the joist in inches.

When accounting for joist width subflooring flooring and standard ceiling drywall a floor framed with 2 by 10s will be very close to 11 1 4 inches thick. No notching or boring anywhere. The same floor if framed with 2 by 12s will be 13 1 4 inches thick. With the same quantity of timber the deeper the joists can be made the stiffer and stronger they are the depth can be calculated by the rules given above or those in.

1 psf lb f ft 2 47 88 n m 2. 2 grade of douglas fir are indicated below. Dead load weight of structure and fixed loads 10 lbs ft 2. So our house would look like the picture below with all floor joists 2 x 8.

Joists in home construction are usually made with 2 by 10 or 2 by 12 lumber. For 19 32 and 5 8 inch panels joists should be 16 or 20 inches on center. See the image below for an example of joists spaced 16 on center 16 o c. Reading the table you ll see that 2 x 8s installed 16 apart on center can span 12 4.