Floor Joist Size In Residential Construction

Solid lumber is generally the most economical choice for joists though price will vary based on wood species board size and lumber grade.

Floor joist size in residential construction.

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. Considering the cross section of a typical joist the overall depth of the joist is critical in establishing a safe and stable floor or ceiling system. Common joist spacings are 12 inches 304 8 mm 16 inches 406 4 mm and 24 inches 609 6 mm. In many countries the fabrication and installation of all framing members including joists must meet building code standards.

Choosing the correct floor joist size depends on your building application joist spacing and several other factors these include the length of the span as well as the type and grade of the lumber being used. In typical deck construction with a ledger on one side of the joist and beam on the other the size of the joists is driven by the size of the deck and based on the general maximum spans mentioned above. Putting all these factors together gives the minimum size joists needed for various types of wood grades of lumber sizes of boards spacing of joists and the load that will be placed on the floor. You should also check your local building codes before starting construction and consult a structural engineer in unusual or extreme situations.

2x10 to 15 feet and 2x12 to 18 feet. A 2x8 up to 12 feet. Floor joist span tables for surveyors floor construction surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors. 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.

The following table gives details of allowable spans and spacing between joists for the most common timber sizes used in floor construction. Joist span and spacing is set by your local building code. True floor joist span calculations can only be made by a structural engineer or contractor. The larger the deck the larger the joists.

Joists must exhibit the strength to support the anticipated load over a long period of time. When building a house or even a deck it is important to confirm you have the correct joist sizes spans and spacing before you get started. Solid lumber joists were once the only option but modern building materials and construction technologies have rendered them less common in new homes.