Ground Floor Timber Joists

Ground floor hollow or timber floor.

Ground floor timber joists.

Creating a vapor barrier only delays the effects of moisture on the wood of the floor. A round timber with one flat surface and in barns long joists were sometimes supported on a sleeper a timber not joined to but supporting other beams. Wood may be sustainably sourced but a lot isn t. The following table gives details of allowable spans and spacing between joists for the most common timber sizes used in floor construction.

The span table for a 30 psf live load 10psf dead load floor indicates a required fb value of 1 315 and a minimum e value of 1 800 000. Building a wooden floor on top of a dirt floor will lead to eventual rotting of even treated wood though the barrier will delay the onset of this for several years depending on the environmental conditions of the building region. Timber floor joists shall be adequate for the spans and loads and be correctly installed. Hollow floors also known as suspended or timber floors are simply timber joists suspended across and supported by load bearing walls under the floor.

Unlike softwood joists timber i joists do not warp over time providing a quiet floor while open metal web joists can provide an easy means of installing services beam and block ground floors the most popular option. Wood and similar structural floor materials timber floorboards. The ends of these timber joists are built into or suspended by joist hangers from the external walls of the property. Joists on the ground floor were sometimes a pole pole joist half round joist log joist.

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. 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. When choosing a timber structural floor layer and timber joists and bearers as well it s important to consider the source of the timber. Joists left out of an area form an opening called a well as in a stairwell or chimney well.

Where the tables do not apply or where there are concentrated loads floor joists should be designed by an engineer in accordance with technical requirement r5. In the example the joists have a spacing of 16 inches and a span of 11 feet 2 inches.