Roof Support Beam Spacing

Although the standard spacing of roof trusses may be the same as that of rafters with 24 inch spacing being a common option the design of a truss may allow for the use of a lower grade of lumber than would be required for rafters with comparable spacing and span.

Roof support beam spacing.

Depending on the roof design and the roof rafter spacing. The beams support the roof rafters or joists which in turn hold the roofing material. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope. In most cases it s much easier to apply a finish.

In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart. If one side of the roof is supported by the house and the other side is supported by the beam divide the total load by two as the beam is only supporting half of the roof. Dimensional lumber deck beam span chart. A roof joist is always spaced no more than 16 inches apart from another roof joist.

The length of joist span actually supported by a beam is what determines the force that bears upon that beam and therefore the distance that a given size of beam can span before another post is required to support that beam. If our example roof has only one beam it must carry half of the total load or 4 000 pounds. Metal roofs and pole buildings. This allows the panels to be securely attached to the rafters for maximum stability.

If a joist spans between two beams or a beam and a ledger each beam or ledger supports half of the joist. When placing rafters for a tin roof also frequently referred to as corrugated metal or steel it is common to set the distance between rafters based on the size of the roofing panels. If there is also a beam in the middle of the roof divide the total load by three. A 2 2x10 can span 10 feet and so on.

Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot. Rafter spacing depends on the roofing panel size. If the roof is not completely square you can decrease the space between joists but never increase the space. A double 2x12 beam can span 12 feet.

The numbers in gray indicate the distance between the support posts. Minimum sizes of posts and beams are set by engineering requirements and are strictly governed by local building codes. When supporting joists that span 12 feet with no overhang beyond the beam a double ply beam can span in feet a value equal to its depth in inches. Before beginning construction consider finishing all of the lumber you will be using.