Roof Joist Depth

No end notches where the joist is supported greater than 1 4 the joist depth.

Roof joist depth.

Flat the most economical flat truss for a roof is provided when the depth of the truss in inches is approximately equal to 7 of the span in inches. The difference in the joist sizes applies to the width of the boards which determines the height of the ceiling. These joists easily handle spans that wood systems cannot handle while their lightweight construction makes them much less costly than steel beams. Considering the cross section of a typical joist the overall depth of the joist is critical in establishing a safe and stable floor or ceiling system.

D out to out depth of the joist in inches el value from table above for tji 110 210 230 and 360 joists δ 22 5 wl4 2 el 2 67 wl2 d x 105 for tji 560 joists δ 22 5 wl4 el 2 29 wl d x 105 material weights include tji weights in dead load calculations see design properties table at left for joist weights. Builders can adjust their choice of lumber size and spacing depending on circumstances. These welded steel products are used to support a building s roof and floors. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak.

Rafter run outer wall this should be measured starting from the center of the roof span and then extending to the very edge of the exterior wall. The maximum depth of a notch at the end of a joist where it rests on a wall or beam can t exceed one quarter of the joist depth. A 2 by 4 inch joist for instance hangs into the room by 4 inches which may leave the ceiling high while a 2 by 12 inch joist in the same position hangs 12 inches into the room which decreases the ceiling height by 8 inches. 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.

About o donnell metal deck. Here the number is 941 86 inches. No notches deeper than 1 6 the joist depth. Most economical when the difference in slope between the top and bottom chords is at least 3 12 or the bottom chord pitch is no more than half the top chord pitch.

No notching in the middle third of a joist. Maximum notch depth in the outer third of a joist is one sixth of the joist depth. The wider the spacing between the joists the deeper the joist will need to be to limit stress and deflection under load. Limit the length of notches to one third of the joist depth.

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. Do not make square or rectangular cutouts.