Minimum sizes of posts and beams are set by engineering requirements and are strictly governed by local building codes.
Roof support beam spacing.
Before beginning construction consider finishing all of the lumber you will be using.
If there is also a beam in the middle of the roof divide the total load by three.
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.
Metal roofs and pole buildings.
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.
A 2 2x10 can span 10 feet and so on.
Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size.
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.
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 a joist spans between two beams or a beam and a ledger each beam or ledger supports half of the joist.
If our example roof has only one beam it must carry half of the total load or 4 000 pounds.
Depending on the roof design and the roof rafter spacing.
Rafter spacing depends on the roofing panel size.
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.
In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart.
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.
The beams support the roof rafters or joists which in turn hold the roofing material.
The numbers in gray indicate the distance between the support posts.
If the roof is not completely square you can decrease the space between joists but never increase the space.
An essential part of planning a patio roof or gazebo project is determining the number size and spacing of rafters beams and posts according to the loads they will carry.
A double 2x12 beam can span 12 feet.
Building codes such as the icc s 2012 international building code section 2308 10 roof and ceiling framing typically specify that where rafter ties are used they are required at intervals ranging from 12 to 24 o c.
A roof joist is always spaced no more than 16 inches apart from another roof joist.
