The pitch of the roof determines the roofing material you can use.
Roof frame spacing.
For heavier material such as gage steel the metal roof purlins spacing length could go up to 4 feet.
For the lighter material such as lightweight aluminum the common spacing length is 4 inches of clear gap.
In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
A super basic a frame roof will require anywhere between 4 and 8 depending on the size of the rafters with plumb cuts necessary for each angle in the brace.
Most roofs utilize 16 inch spacings for strength and rigidity.
Very simple trusses work on a principle of thirds.
It must meet the local codes for thickness at least 3 8 which is also based on the rafter or truss spacing.
There are special shingles available for 2 12 but you re better off using other materials.
Stick framing combines roof rafters with ceiling joists.
As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes.
The rise or height of the roof at its peak is the altitude of the triangle.
Asphalt shingle can be installed on a pitch of 2 over 12 or greater.
The tables below give maximum spans for rafters and beams.
Stockbyte stockbyte getty images 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.
The figures are based on quality materials.
A roof truss is a structural framework usually made from wood that bridges the space between the ceiling of the top level and the roof structure.
If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.
The run or half the building span is the base of the triangle.
Like wall studs and floor joists rafters and trusses are spaced every 16 or 24 inches from center to center.
Metal roofs and pole buildings.
Designing roof trusses for proper placement on post frame buildings.
And the line length measurement from the roof peak to the building wall is the hypotenuse.
The framing of a basic gable roof is based on a right angle triangle and the various roof framing components fit the triangle.
The rafters are usually positioned directly above the wall studs.
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.
For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.
