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How to calculate roof height at ridge given roof slope & building width (C) Daniel Friedman Roof Slope Table

  • ROOF SLOPE TABLE, TYPES, WALKABILITY - CONTENTS: Table of roof rise, run, slope, types, & walkability, complete table of roof slope, rise/run, walkability, angle or slope expressed as grade, and classification of roofs as flat, low slope, and steep slope. Definition of low slope & steep slope roofs.
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Roof slope, pitch, rise, run, typw & walkability table:

This table lists all of the common roof slopes expressed as rise / run, roof angle, roof slope, slope grade, and walk-ability.

This article series gives clear examples just about every possible way to figure out any or all roof dimensions and measurements expressing the roof area, width, length, slope, rise, run, and unit rise in inches per foot.



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Table of Roof Slopes, Roof Types, Walkability

A-frame roof structure, Hovland Minnesot (C) Daniel Friedman

The A-frame style roof shown just above, located on Highway 61 just South of Hovland Minnesota, is built at a 75° angle and is considered a very-steep roof. The table below describes different roof slopes, giving roor slope in rise/run in inches and re-expressing the same slopes as angle, grade, walk-ability, and roof type or class. [Click to enlarge any image]

Common Roof Slopes Expressed in Rise/Run and Angle + Slope expressed as Grade

Roof Slope Expressed as Rise / Run in Inches Roof Slope Expressed as an Angle Grade  Walkability Roof Type
0 / 12  0 ° or 180 ° 0 % Easy to walk on Flat Roof
1 / 12 4.76 ° 8.33% Grade Low-Slope Roofs
2 / 12 9.46 ° 16.67%
3 / 121 14.04 ° 25.0%
4 / 12 18.43 33.33% Steep Slope Roofs
5 / 12 22.62 ° 41.67%
6 / 12 26.57 ° 50%
 
7 / 12 30.26 ° 58.33% Walkable, but with caution
 
8 / 12 33.69 ° 66.67% Walking not advised, use extreme caution
9 / 12 36.37 ° 75%
10 / 12 39.81 ° 83.33%
   
11 / 12 42.51 ° 91.67% Too steep to walk-on, roof-jacks, scaffolding, affixed ladders, etc. needed for installation, inspection, repair
12 /12 45 ° 100 % Grade
13 / 12 47.29 ° 108.33%
14 / 12 49.4 ° 116.67%
15 / 12 51.34 ° 125% Grade
16 / 12 53.13 ° 133.33%
17 / 12 54.78 ° 141.67% Grade
18 / 122 56.31 ° 150% Grade
19 / 12 57.72 ° 158,33%
20 / 12 59.04 ° 166.67%
21 / 12 60.26 ° 175% Grade
22 / 12 61.39 ° 183.33%
23 / 12 62.45 ° 191.67%
24 / 123 63.43 ° 200 % Grade
48 / 12 76 ° 400 %
72 / 12 80.5 ° 600 %
120 / 12 84.3 ° 1000 %
9999999 (infinity) / 12 90 ° 8333325 %

Notes:

1. Low slope roofs are from 0 to 3 / 12 in pitch. Some sources consider low slope to include 3 / 12 pitch roofs. If asphalt shingles are to be installed on a low slope roof, special steps are required to avoid short roof life and roof leaks.
See LOW SLOPE ROOFING

2. Slopes greater than 18 / 12 are found on A-frame roofs and some Mansard style roofs. Clearly once we get near 90 ° we're describing a wall, not a roof, that is vertical or near-vertical surface.
Also see ROOF ARCHITECTURAL STYLES

3. If asphalt shingles are to be applied on steep slope roofs or on near-vertical surfaces, special methods are required.
See ASPHALT SHINGLES on VERY STEEP ROOFS

See ROOF MEASUREMENTS for an explanation of all of the ways to measure roof slope, size, area, etc. from the ground, the air, from inside the attic, or from on the roof.

See ROOF SLOPE DEFINITIONS for definitions of rise, run, roof slope, pitch, angle, grade.

Table © 2016 InspectApedia.com Daniel Friedman

Roof slope definitions and illustrations (C) Carson Dunlop Associates

[Click to enlarge any image]

The illustration of roof slope types shown above is provided courtesy of Carson Dunlop Associates, a Toronto Home Inspection and Home Inspection Education firm.

Building & Roof Measurement Articles

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Continue reading at ROOF SLOPE DEFINITIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see ROOF FRAMING TIES & BEAMS collar ties, rafter ties, tension ties, structural ridge requirements

Or see ROOF SLOPE CALCULATIONS for an explanation of various ways to calculate slope, pitch, or grade.

Or see ROOF MEASUREMENTS where we describe all of the methods for measuring roof slope, area, etc.

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ROOF SLOPE TABLE, TYPES, WALKABILITY at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ROOFING

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