Size Of Timber Floor Joists

Joist span and spacing is set by your local building code.

Size of timber floor joists. In fact there are no standard joist sizes and the joist spacing depth thickness wood type and load capacity must also be considered before ordering. Some newer homes have manufactured i beam shaped joists. All the figures are based on normal domestic floor loadings where the floor construction is typically 18 25mm floor boards sheets with up to 12 5mm thick plasterboard and skim underneath. A floor s framework is made up mostly of wooden joists that run parallel to one another at regular intervals.

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. These tables can help calculate whether floor joists are strong enough to support themselves and the load they carry without the help of any walls underneath. 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. If the joist spacing will be 16 inches 406 4 mm a joist size of 2 x 8 should be used even if the length is only 8 feet 2 44 m.

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. Even when a contractor knows which kind of joists would be best for a specific project he can t just go about placing an order with nothing but floor joist spans to guide him. Floor joists capacities carrying capacities of domestic timber floor joists grade c in metric units floors live loads floors and minimum uniformly distributed live loads maximum size of duct or pipe through steel joists k series joists and maximum size of ducts and pipes. Find the column for your dead load and spacing and the row for your timber size to find the permissible clear span in metres.

These spans were calculated using our floor joist calculation engine. Floor joists or beams provide the below surface support for the wood subfloor of a room. Ceiling joists are usually 2 by 6s or sometimes 2 by 4s if it is an older home. Click on a span to generate a full calculation you can adjust the exact span.

The following table gives details of allowable spans and spacing between joists for the most common timber sizes used in floor construction. Though joists may be any size that you desire using typical floor joist and beam specifications ensures that you can find hardware to fit the joists and that the floor provides adequate support for furniture and other items in a room. Surveyors and structural engineers use data from tables below to help calculate the size of timbers necessary to give adequate support to timber floors.