Floor Joist Timber Floor Construction Methods

Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor.

Floor joist timber floor construction methods. Floor joists are typically 2 by 8s 2 by 10s or 2 by 12s. Building and understanding a suspended or hollow timber floor. 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. Some newer homes have manufactured i beam shaped joists.

The following table gives details of allowable spans and spacing between joists for the most common timber sizes used in floor construction. The international building code is a model code that has been adopted by all 50 states as well as the district of columbia. This problem can be solved by installing a beam in the floor joist system and hanging the floor joists on the beam. A floor s framework is made up mostly of wooden joists that run parallel to one another at regular intervals.

The beam is typically sized to be the same height as the floor joists. When a load is applied to a joist the wood fibers along the bottom edge go into tension and those along the top go into compression fig. Make sure to use construction adhesive in the seat of the hanger to prevent floor squeaks. Rather the reader is referred to the aisi standard for cold formed steel framing prescriptive method for one and two family dwellings aisi 2001 for guidance.

We explain how hollow or suspended floors are made and what the key building regulations that affect them are. But larger is not always better when builders are constructing a home or adding a room addition. 69 chapter 4 floor construction woodframe floor systems and concrete slab on grade floors are discussed in this chapter. Apa performance rated i joists pris are manufactured in accordance with pri 400 performance standard for apa ews i joists form x720 this performance standard provides an easy to use table of allowable spans for applications in residential floor construction allowing designers and builders to select and use i joists from various member manufacturers using just one set of span.

Although cold formed steel framing for floor systems also is permitted by the irc it is not covered here. A related code the residential building code has been adopted by all states except wisconsin. Purchase the type of lumber that matches the width of the existing joist. Most new construction uses 2 by 8 lumber for joists although 2 by 6.

The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example. Measure the width and length of the existing joist. Ceiling joists are usually 2 by 6s or sometimes 2 by 4s if it is an older home.