Bottom Chord Attic Not Connected

The architect had drawn in an attic condition that stepped up and over the floor joists at one end of the building.

Bottom chord attic not connected.

See table r301 5 for the above and then this note below the table. A triangle is the simplest form of a truss and the bottom chord is the base piece. Where ceiling joists are not parallel to rafters rafter ties shall be installed. In other words the attic truss had no bottom chord.

Attic with storage is 20 psf versus 10 psf for attic with no storage. The design was 2 mono trusses sistered together at a ridge girder over the attic space. The bottom chord therefore carries combined stress of both tension and bending of the truss. Lay a 2 by 4 across the truss with its bottom end on the top edge of the lower cord and centered on the mark you made between the end of the truss and its center.

Several common wood truss splice joint configurations were tested at varying levels of. A the top and bottom chord dead load. O limit attic room bottom chord l d to max 23 for example attic truss with 2x10 bottom chord lumber in the room should not have room wider than 17 9. Attics without storage are those where the maximum clear height between joist and rafter is less than 42 inches or where there are not two or more adjacent trusses with the same web configuration capable of containing a rectangle 42 inches high by.

A rafter tie forms the bottom chord of a simple triangular roof truss. This anomaly did not make it into the 3rd printing of asce 7 10 in 2013 but did create a discrepancy in the 2012 2015 irc. O no top chord splices in haunch of attic room as shown below. Plating o do not reduce minimum plating defaults.

About the bottom chord. The horizontal beam of the triangle of a bottom chord is used in this simple triangle truss construction. Recently a project came across our desk that was an unusual attic design. Given that this section of the bottom chord is likely where one of the connector plates that hold the truss together is located you may need to nail through a metal plate on one side of the truss.

Metal plate connected mpc splice joints were tested in combined tension and bending to generate data that were used in the development of a design procedure for determining the steel net section strength of bottom chord splice joints of mpc wood trusses. Center the 2 by 4 on the mark on the upper cord as well so that it extends from the lower cord at a 90 degree angle. O no bottom chord splice directly over a bearing within a room. Where ceiling joists are not connected to the rafters at the top wall plate joists connected higher in the attic shall be installed as rafter ties or a continuous tie should be provided.

D sketch the loading diagram and calculate the reactions. The remaining portions of the bottom chords shall be designed for a uniformly distributed concurrent live load of not less than 10 lb ft2 0 48 kn m2. The attic space is considered uninhabitable but will be used for storage. B the top chord live include snow load as a live load and bottom chord live load.