Laying Out Floor Joists

The floor joist spacing is the distance between the centers of any two installed joists.

Laying out floor joists.

It s important to lay out floor joists correctly. Remove any screws or fasteners that may be protruding from the surface of the joist. Floor joists are typically 2 by 8s 2 by 10s or 2 by 12s. You ll use the same size lumber to assemble the rim joists as you will for the main floor joists.

Use a water management system such as a drip cap or flashing wherever framing meets the home to move moisture away from the home and deck. Tack a 2x block to the rim joist at the house. Joists range in size from 2 x 6 to 2 x 12 based on the distance being spanned. The rim joist sits vertically on top of the sill plate along the outside of the frame to create a lip for the main floor joists.

The rim joist is not going to help you build the deck floor because you won t trim the deck joist outer ends to an exactly uniform length until all of them are in place. On this deck the extended joists were sistered on the side with the blocks meaning that the new joist layout was offset by 1 1 2 in. True floor joist span calculations can only be made by a structural engineer or contractor. Joists are generally 2 by 8 inch or 2 by 10 inch boards.

Measure the size of the area where you are laying out the floor joists to determine how many joists you need. A floor s framework is made up mostly of wooden joists that run parallel to one another at regular intervals. 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. Ceiling joists are usually 2 by 6s or sometimes 2 by 4s if it is an older home.

Laying out the rim joist is an optional step and one i have never seen a carpenter do but according to some it does come in handy when you need to check to see that the. Tack another 2x block to the rim joist over the first beam and then extend a string line that s aligned with the blocks to transfer the layout. For most jobs 2 in 5 1 cm x 10 in 25 cm boards are an ideal size. See the image below for an example of joists spaced 16 on center 16 o c.

Joists must be level and in plane for a flat surface. Look for high low uneven joists using a tight string line. Laying a floor joist in a wood frame house is a simple procedure that can be done in 4 easy steps. Wood joists are structural framing members that are laid upright on edge and nailed equally spaced usually 16 inches on center onto the wall plates.

Some newer homes have manufactured i beam shaped joists.