Depth Of Floor 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.

Depth of floor joists.

The floor joist spacing is the distance between the centers of any two installed joists. The bulk of the floor s thickness comes from the joists which are the horizontal beams that carry the floor s weight. 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. Reading the table you ll see that 2 x 8s installed 16 apart on center can span 12 4.

No notching in the middle third of a joist. To this number add 2 for the depth of the joist in inches. Maximum floor joist span for no. Builders can adjust their choice of lumber size and spacing depending on circumstances.

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 maximum depth of a notch at the end of a joist where it rests on a wall or beam can t exceed one quarter of the joist depth. For 19 32 and 5 8 inch panels joists should be 16 or 20 inches on center. So our house would look like the picture below with all floor joists 2 x 8.

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. Half this is 9 add 2 which gives 11 inches for the depth. 1 ft 0 3048 m. Joists in home construction are usually made with 2 by 10 or 2 by 12 lumber.

No notching or boring anywhere. Maximum notch depth in the outer third of a joist is one sixth of the joist depth. Limit the length of notches to one third of the joist depth. E g for a span of 18 feet.

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. Joist span and spacing is set by your local building code. 2 grade of douglas fir are indicated below. See the image below for an example of joists spaced 16 on center 16 o c.

Dead load weight of structure and fixed loads 10 lbs ft 2. Live load is weight of furniture wind snow and more. For 23 32 and 3 4 inch panels joists should be 24 inches on center. You should check with your local building department for construction requirements in your area.