Roof pitch is the steepness of a roof expressed as a ratio of inch(es) rise per horizontal foot (or their metric equivalent), or as the angle in degrees its surface deviates from the horizontal. A flat roof has a pitch of zero in either instance; all other roofs are pitched.
Display of roof pitches 1/12 through 18/12A roof made of thatch, one of the oldest roofing materials, needs a steep pitch to drain properlySome types of stone roof have a very restrictive roof pitch, which can lead to leakingWorking on roofs with pitches too steep for safety requires a staging of scaffolding boards secured with roof brackets
A roof that rises 3 inches per foot, for example, would be described as having a pitch of 3 (or “3 in 12”).
The pitch of a roof is its vertical 'rise' over its horizontal 'run’ (i.e. its span), also known as its 'slope'.
In the imperial measurement systems, "pitch" is usually expressed with the rise first and run second (in the US, run is held to number 12;[1] e.g., 3:12, 4:12, 5:12). In metric systems either the angle in degrees or rise per unit of run, expressed as a '1 in _' slope (where a '1 in 1' equals 45°) is used. Where convenient, the least common multiple is used (e.g., a '3 in 4' slope, for a '9 in 12' or '1 in 1 1/3').
SelectionEdit
Considerations involved in selecting a roof pitch include availability and cost of materials, aesthetics, ease or difficulty of construction, climatic factors such as wind and potential snow load,[2] and local building codes.
The primary purpose of pitching a roof is to redirect wind and precipitation, whether in the form of rain or snow. Thus, pitch is typically greater in areas of high rain or snowfall, lower in areas of high wind. The steep roof of the tropical Papua New Guinealonghouse, for example, sweeps almost to the ground. The high, steeply-pitched gabled roofs of Northern Europe are typical in regions of heavy snowfall. In some areas building codes require a minimum slope. Buffalo, New York and Montreal, Quebec, Canada, specify 6 in 12, a pitch of approximately 26.6 degrees.[3]
A flat roof includes pitches as low as 1/2:12 to 2:12 (1 in 24 to 1 in 6), which are barely capable of properly shedding water. Such low-slope roofs (up to 4:12 (1 in 3)) require special materials and techniques to avoid leaks.[4]Conventional describes pitches from 4:12 (1 in 3) to 9:12 (3 in 4).[4]Steep is above 9:12 (3 in 4)[4] (21:12) (7 in 4) and may require extra fasteners.
US convention is to use whole numbers when even (e.g. "three in twelve") or the nearest single or two-digit fraction when not (e.g. either "five and a half in twelve" or "five point five in twelve", each expressed numerically as 5-1/2:12 and 5.5:12) respectively.
Definitions vary on when a roof is considered pitched. In degrees, 10°(2 in 12 or 1 in 6) is considered by at least one reference a minimum. [5]
In trigonomic expression, exact roof slope in degrees is given by the arctangent. For example: arctan(3/12)=14.0°
Framingcarpenters cut rafters on an angle to "pitch" a roof. Lower pitched roof styles allow for lower structures with a corresponding reduction in framing and sheathing materials.
Historic expressions of roof pitchEdit
A building in the Black Forest of Germany with a pitched roof
Historically, roof pitch was designated in two other ways: A ratio of the ridge height to the width of the building (span)[6] and as a ratio of the rafter length to the width of the building.[7]
Commonly used roof pitches were given names such as:
Greek: the ridge height is 1/9 to 1/7th the span (an angle of 12.5° to 16°);
Roman: the ridge height is 2/9ths to 1/3 the span (an angle of 24° to 34°);
Common: the rafter length is 3/4 the span (about 48°);
Gothic: the rafters equal the span (60°); and
Elizabethan: the rafters are longer than the span (more than 60°).[7]
^"Pitch" Sturgis, Russell. A dictionary of architecture and building: biographical, historical, and descriptive. New York: The Macmillan Co. ;, 1901. 152. Print.
^[1] Miter angles and miter saws, thisiscarpentry.com
^ abc"Slope" def. 1. Schmid, Karl F.. Concise encyclopedia of construction terms and phrases. New York: Momentum, 2014. Print.
^Dictionary of Architecture & Construction, C.M.Harris.
^ ab"Pitch" def. 2. Knight, Edward Henry. Knight's American mechanical dictionary: being a description of tools, instruments, machines, processes, and engineering; history of inventions; general technological vocabulary; and digest of mechanical appliances in science and the arts.. vol. 2. New York: J.B. Ford and Co., 1874. 1719. Print.
External linksEdit
How to determine roof pitch
Roof pitch calculator
Online roof pitch calculator
Aerial Roof Measurements
September 27, 2023
roof, pitch, steepness, roof, expressed, ratio, inch, rise, horizontal, foot, their, metric, equivalent, angle, degrees, surface, deviates, from, horizontal, flat, roof, pitch, zero, either, instance, other, roofs, pitched, display, roof, pitches, through, roo. Roof pitch is the steepness of a roof expressed as a ratio of inch es rise per horizontal foot or their metric equivalent or as the angle in degrees its surface deviates from the horizontal A flat roof has a pitch of zero in either instance all other roofs are pitched Display of roof pitches 1 12 through 18 12A roof made of thatch one of the oldest roofing materials needs a steep pitch to drain properlySome types of stone roof have a very restrictive roof pitch which can lead to leakingWorking on roofs with pitches too steep for safety requires a staging of scaffolding boards secured with roof bracketsA roof that rises 3 inches per foot for example would be described as having a pitch of 3 or 3 in 12 Contents 1 Description 2 Selection 3 Historic expressions of roof pitch 4 See also 5 References 6 External linksDescription EditThe pitch of a roof is its vertical rise over its horizontal run i e its span also known as its slope In the imperial measurement systems pitch is usually expressed with the rise first and run second in the US run is held to number 12 1 e g 3 12 4 12 5 12 In metric systems either the angle in degrees or rise per unit of run expressed as a 1 in slope where a 1 in 1 equals 45 is used Where convenient the least common multiple is used e g a 3 in 4 slope for a 9 in 12 or 1 in 1 1 3 Selection EditConsiderations involved in selecting a roof pitch include availability and cost of materials aesthetics ease or difficulty of construction climatic factors such as wind and potential snow load 2 and local building codes The primary purpose of pitching a roof is to redirect wind and precipitation whether in the form of rain or snow Thus pitch is typically greater in areas of high rain or snowfall lower in areas of high wind The steep roof of the tropical Papua New Guinea longhouse for example sweeps almost to the ground The high steeply pitched gabled roofs of Northern Europe are typical in regions of heavy snowfall In some areas building codes require a minimum slope Buffalo New York and Montreal Quebec Canada specify 6 in 12 a pitch of approximately 26 6 degrees 3 A flat roof includes pitches as low as 1 2 12 to 2 12 1 in 24 to 1 in 6 which are barely capable of properly shedding water Such low slope roofs up to 4 12 1 in 3 require special materials and techniques to avoid leaks 4 Conventional describes pitches from 4 12 1 in 3 to 9 12 3 in 4 4 Steep is above 9 12 3 in 4 4 21 12 7 in 4 and may require extra fasteners US convention is to use whole numbers when even e g three in twelve or the nearest single or two digit fraction when not e g either five and a half in twelve or five point five in twelve each expressed numerically as 5 1 2 12 and 5 5 12 respectively Definitions vary on when a roof is considered pitched In degrees 10 2 in 12 or 1 in 6 is considered by at least one reference a minimum 5 In trigonomic expression exact roof slope in degrees is given by the arctangent For example arctan 3 12 14 0 Framing carpenters cut rafters on an angle to pitch a roof Lower pitched roof styles allow for lower structures with a corresponding reduction in framing and sheathing materials Historic expressions of roof pitch Edit nbsp A building in the Black Forest of Germany with a pitched roofHistorically roof pitch was designated in two other ways A ratio of the ridge height to the width of the building span 6 and as a ratio of the rafter length to the width of the building 7 Commonly used roof pitches were given names such as Greek the ridge height is 1 9 to 1 7th the span an angle of 12 5 to 16 Roman the ridge height is 2 9ths to 1 3 the span an angle of 24 to 34 Common the rafter length is 3 4 the span about 48 Gothic the rafters equal the span 60 and Elizabethan the rafters are longer than the span more than 60 7 See also EditList of roof shapes Shed roof Flat roof Types of Pitched roofReferences Edit Roof Slope Multiplier Roof Online Retrieved 2018 05 19 Pitch Sturgis Russell A dictionary of architecture and building biographical historical and descriptive New York The Macmillan Co 1901 152 Print 1 Miter angles and miter saws thisiscarpentry com a b c Slope def 1 Schmid Karl F Concise encyclopedia of construction terms and phrases New York Momentum 2014 Print Dictionary of Architecture amp Construction C M Harris Pitch def 24 c Oxford English Dictionary Second Edition on CD ROM v 4 0 c Oxford University Press 2009 a b Pitch def 2 Knight Edward Henry Knight s American mechanical dictionary being a description of tools instruments machines processes and engineering history of inventions general technological vocabulary and digest of mechanical appliances in science and the arts vol 2 New York J B Ford and Co 1874 1719 Print External links EditHow to determine roof pitch Roof pitch calculator Online roof pitch calculator Aerial Roof Measurements Retrieved from https en wikipedia org w index php title Roof pitch amp oldid 1162371412, wikipedia, wiki, book, books, library,
