Bottom Bearing Floor Trusses

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.

Bottom bearing floor trusses. The live loads a truss is required to bear are determined by local building codes. Spans shown are in feet 4. Each type of floor joist offers its own unique benefits and drawbacks which is why those working in carpentry all tend to have their own favorite floor joist option though they are still required to be well versed in each type of floor framing. Inclined or horizontal member that establishes the bottom of a truss usually carrying combined tension and bending stresses.

Maximum 30 2 6 top chord panel length on flat wise trusses. Structural support usually a beam wall or post that is designed by the building designer to carry the truss reaction loads to the foundation. Maximum 48 4 top chord panel length on edgewise trusses. Ridge line formed by truss apexes.

Tcdl 10 psf and bcdl 5 psf 3. 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. The three main types of floor joists used in home construction are solid lumber i joists and open web floor trusses. A preassembled unit of floor joists subflooring.

Floor trusses offer four different bearing conditions for a wider variety of uses. Reaction the total load transferred from the uniform load psf applied to the floor truss deck then into the floor truss and ultimately to the floor truss bearing or support. If the bottom chord of a roof truss functions as a floor joist such as in an attic room it carries a live load that also varies by use but a typical live floor load for a residential space is about 40 pounds per square foot. Girder floor truss floor truss jacks a a bearing wall girder floor truss floor truss jacks bearing wall cantilevered floor truss two 2x rim joists 24 max.

Tcll top chord floor live load 2. Additional support for the floor joists is achieved by nailing the ends of the joists into headers. Section r502 10 of the international residential code states that header joists can be the same size as the floor joists when the header joist span isn t greater than 4 feet but if the header joist span is more than 4 feet you ll need to double the header joist and ensure that it s capable of. But larger is not always better when builders are constructing a home or adding a room addition.

Live load l 480 total load l 360 5. Top and bottom chords braced by structural sheathing 6. Roof floor truss manual 7 31 08 10 43 am page 12. The multiple bearing conditions make matching existing floor heights much easier when using floor trusses.

Rim joistan exterior transition member. Floor trusses maximum span to depth ratio of 20 for example a 14 deep truss should not exceed a span of 23 4. Elements that make a floor truss. Minimum duct chase offset from the bearing is of the truss span.