Roof Pitch - How to find the best roof pitch for your metal, slate, tile or asphalt roofing material.
Pitch - The slope of the rafters as determined by both the rise and the run of the roof.
Rise is the vertical distance between the ends of a slope. Or the distance between the eave(bottom gutter line) and the ridge or top of the roof.
Run is the horizontal distance between the ends of a slope.
Pitch is commonly referred to as vertical distance in inches to horizontal distance in 12 inches.
For example; 1-12, 3-12, 12-12, or 1 in 12, 12 in 12, etc.
For a better full size diagram of roof slopes in rise and run, pitches and degrees click here Roof_pitch_degree.jpg
The pitch of the roof should be determined by both the local climate, against which it is to act as a protection, and the roofing materials being installed.
Although there are no hard and fast rules regarding roof pitches, it is best to design the roof with slope suitable to local conditions and to use roofing materials best adapted to meet the climatic changes.
In hot and dry regions of the country, the roof needs only enough pitch to shed water; but the roof must be well constructed and water tight, to be able to handle the large but short lived volume of rain that is common in those areas.
1/2 - 12, or 4 Degrees to 3 - 12, or 15 Degrees for the roof pitch and materials such as Coal Tar Pitch, Hot built up roofing, single-ply membranes, or modified bitumens.
In colder and temperate areas of the country, rain and snow are driven by high winds and the pitch of the roof should to be steep to shed the more frequent rain and and build up of snow.
4 - 12, or 20 Degrees to 12 -12 or 45 Degrees and up for the roof pitch and materials such as Slate, Tile, Metal or Asphalt compostition shingles.
Architecturally, the roof pitch is determined by the style to which they belong.
For Grecian design, a roof pitch of 12 to 16 Degrees or 2 1/2 - 12, to 3 1/2 - 12
The Parthenon is a good example.
For Roman design, a roof pitch of 23 to 24 Degrees or 5 - 12
For Gothic design, a roof pitch of 45 Degrees or 12 - 12
For Elizabethan design, a roof pitch of 60plus Degrees or 22 - 12 to 24 - 12
To find the pitch of your roof, simply hold a 12 inch ruler level with the edge of your roof shingles with the ruler tip on the shingles and the end towards the roof peak. At the inside end of the ruler, measure vertically to get your pitch.
Roof pitch, the angle/slope of a roof plane, should not be confused with coal tar roof pitch. Coal tar roof pitch is a type of coal tar bitumen that is used in built-up roof systems(BUR) using coal tar saturated roofing felt. Coal tar roof pitch is used on dead level roof structures and works very well.
For many roofing materials, the pitch of the roof needs to be within a certain range. Coal tar pitch, asphalt built-up, lead sheet, all require a rather low slope to perform well. Asphalt shingles, slate and tile roofing can withstand a wider range of roof pitch. Copper sheet metal is probably the best all around performer in any situation, both as water proofing and aesthetics.
Copper roofing can be used with no pitch, as in this pond liner;
Recommended pitch for tile roofing.
For tile roofing, minimun pitch standards should be followed to ensure a watertight system. For low pitched roofs proper underlayment must be used.
Interlocking shingle tiles like the Ludowici Americana, Classic,Lanai etc should be set at a minimum 3/12 pitch.
One piece barrel tiles similar to the Ludowici Spanish tile should have a minimum of 4/12 pitch.
Two piece barrel tiles, Mission,Cubana and flat shingle or slab tiles like the Norman or Provincial need a minimum of 5/12 pitch.
