To use the direct roof slope measurement procedure shown just abofe, in addition to safe access to a roof that won't be damaged by touching or walking on it, you need: a tape measure and a carpenter's level. Tan-1 (1.43) = 55 deg. What if the roof is inaccessible from outdoors, and there is no access to the building interior (i.e. Now let's figure run for 12" of rise for an 81 degree slope - HOLD ON! Griffin, Mcgraw-Hill (Tx); 2nd edition (July 1982), ISBN-10: 0070247838, ISBN-13: 978-0070247833, Concrete Folded Plate Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author), Butterworth-Heinemann, 1998, ISBN-10: 0340662662, ISBN-13: 978-0340662663. Apologies for the delay. In my sketch above if we travel up my triangle along (a) from left to right, we will cross a horizontal distance (b) and we will ascend in height an amount (c). Multiply the hypotenuse by the length of the roof. So really I could go just 9 degrees off of flat. Step 2: Determine leader size. This is often used in mechanical engineering and architectural engineering related fields, specifically hardness testing, axial stress, wind pressures, and terminal velocity.. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also, Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com. The roof area (RA) is calculated easily: we multiply the Roof Length (c) (which is the sum of building length plus the gable end overhangs of the roof) by the Roof Width of slope (a) that we just figured out above when we computed the hypotenuse of the roof triangle (that's why we needed the roof rise number). John Wiley & Sons, 2006. Roof Pitch = rise / run = Roof Slope = Tangent Function. Thanks 01-14-2005, 06:49 PM #2. slatta. If the mean annual rainfall is 252 cm .A horizontal projected roof area is 460 m² . Measure straight down to the roof surface from the mark you just made - the blue line in our sketch. For more complex roof lines with multiple pitch angles, it's a little more complicated but the same steps can be followed; just break down the roof into separate sections with a different square footage for each different pitch angle. Divide your roof pitch by 12. Total roof area - 500' by 200' = 100,000 sq. RL is simply the building width plus the amount of overhang at the two gable ends of the building. For an outdoor version of this same approach see our example of MEASURING ROOF SLOPE OUTSIDE at the gable end of a building. ft. or .0312 gallons per minute/sq. Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of "Choosing Roofing," Jefferson Kolle, January 1995, No. So you're thinking of reroofing the house yourself and want an estimate for how much roofing … That's how I used the angle finder shown until someone ran over my steel framing square, forcing me to buy a new (aluminum model). This distance (green arrow in our photo) is the roof rise in inches per foot of run. Congress Catalog Card Nr. The official website of Massachusetts Attorney General Maura Healey. Learn more, get an estimate and connect with providers. Steep slope roofing is generally referred to as “residential roofing” due to the fact that most single family homes in the U.S. are framed with a steep slope roof pitch. The answer is I was holding my angle level on the wrong scale. Next, square your result. 3 inches c. 5 inches d. 6 inches. This would yield 1/3.) This calculation will give a solid estimate for a single slope roof and a simple gable roof with a single pitch. E.g. The minimum size of a horizontal rain water pipe with a 1/8 inch per foot slope, serving a roof with a projected area of 10,700 square feet, and a rainfall rate of 2 inches per hour is _____. Another simplistic approach used by some estimators is to ignore complex roof structure, just measuring the building's footprint and the roof slope - an approach that gets you into the right "ballpark" but will very seriously under-estimage the roof area for steep slope roofs. Print. Roof width (a): This data allows us to calculate the roof triangle as we know two sides (b) and (c) of the three sides of a right triangle (the red lines in our photo at above left). We use the level to measure out from the roof surface horizontally for a distance of 12". 2 inches b. Rosemont, IL 60018-5607, Tel: (847) 299-9070 Fax: (847) 299-1183. copy on file as /roof/Roofing_Historic_NPS .pdf Roofing for Historic buildings", Sarah M. Sweetser, Preservation Brief 4, Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_3 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals-part II, Coated Ferrous Metals: Iron, Lead, Zinc, Tin, Terne, Galvanized, Enameled Roofs", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_4 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals-part III, Slate", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_5 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals-part IV, Wood", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_5 .pdf From Asbestos to Zinc, Gutters", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_2 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals- Roofing Today", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: copy on file as /exterior/NPS_Preserv_Brief_16_Subs_Mtls.pdf The Use of Substitute Materials on Historic Building Exteriors ", Egad! For example, a 3 inch per hour rainfall will build up to a 3 inch depth on a flat roof in one hour, at the rate of 1.87 gallons per hour/sq. [1] "How to Measure Angles with a Ruler", South Dakota School of Mines and Technology, Website: http://www.mcs.sdsmt.edu, http://www.mcs.sdsmt.edu/tkowalsk/portfolio/downloads/pub_HowToMeasureAngles.pdf retrieved 10/26/2013, copy on file. Tan -1 is the inverse of a Tangent which will convert any rise/run ratio back to degrees. Whew! Projected area is the two dimensional area measurement of a three-dimensional object by projecting its shape on to an arbitrary plane. Dividing by 12 gives the ratio of inches in rise per distance. The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com, A long-standing use of the framing square that is missed by many new carpenters is the rafter table imprinted right on the framing square itself. Now what? 92. E.g. R4413.6.5 Parapet wall … Click to Show or Hide Citations & References, Multiplier to convert a flat horizontal a. The third side of the triangle, its hypotenuse or the sloping surface of the roof, or side is (a) which is calculated as follows: a2 = b2 + c2 - the square of the length of the hypotenuse (a) equals the squares of the lengths of the opposite sides of a right triangle (b) and (c). Can anyone point me to a resource that provides a definition of the horizontal projected area of a cone? This is a low slope roof, how can it be sloping 81 degrees? Off (1963), ASIN: B0007FTV2Q, Tile Roofs of Alfred: A Clay Tradition in Alfred NY, "Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE, Wood Shingle Roofs, Care and Maintenance of wood shingle and shake roofs, (EC), Stanley S. Niemiec (out of print). See the following. Question: If The Mean Annual Rainfall Is 252 Cm .A Horizontal Projected Roof Area Is 460 M² . Yes, any roof overhangs that can be used for expansion of the building’s exterior walls, such as attached covered entry’s, are part of the building area. Stewart, Thomas A., "Owens-Corning: Back from the Dead," Fortune, May 26, 1997. International Directory of Company Histories, Vol. According to the chart, for 1/8” slope per 12” of pipe, for 5,000 square feet of roof area, with a 6” per hour of rainfall, the required pipe size is 8”. Using a 10,000 sq. Asphalt Roofing Residential Manual from ARMA the Asphalt Roofing Manufacturers Association Website https://www.asphaltroofing.org/product/residential-asphalt-roofing-manual/ , Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724 For more accurate angle or slope measurements, for example on a rough shingle surface outdoors, use a straight edge between the angle finder level and the roof surface to give a longer footprint for the sensor. From Table 1 - one 4" leader at 4" rate of rainfall will take care of 3,460 sq. If we start counting siding at a horizontal lilne even with the lower roof edge or eaves and count up to the ridge, we've got a close guess at the total roof rise. Generally, roofing types and roofing products are typically divided up into two primary categories, steep slope roofing and low slope roofing. "Two-Year Wisconsin Thermal Loads for Roof Assemblies and Wood, Wood–Plastic Composite, and Fiberglass Shingles [on file as Roof_Thermal_Loads.pdf] - ", From a ladder or other accessible area giving safe access to the sloping gable end trim or roof edges. At one time a building code defined the roof extension had to be used in the building area if the roof extension was 15-ft or greater. Measuring the roof slope, pitch, or rise and run is easy if you've got a tape measure and more accurate still if you've also got a level on hand. With a decent 3/4" or 1" wide 30 ft. tape measure you can extend the tape out to catch the roof eaves without having to walk dangerously close to the roof edge. But to understand how some people use a flat or horizontal projection of a roof to guess at roof area, here is the procedure. Below is a tiny summary that shows the range of these values. and wonderfully, Tan-1 (1.00) = 45 deg. ROOF MEASUREMENTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice. We can use the TAN or tangent feature of a calculator as a trivial way to convert degrees of slope (or grade if we're building a sidewalk or road) into units of run per unit of rise. The maths behind this number is that it is the square root of ((rise/run) 2 + 1). A complete table of roof slopes expressed as rise / run, slope, and grade is given at ROOF SLOPE TABLE, TYPES, WALKABILITY. Slate Roofing in Canada (Studi4es in archaeology, architecture, and history), Smart Guide: Roofing: Step-by-Step Projects, Creative Homeowner (Ed), 2004, ISBN-10: 1580111491, ISBN-13: 978-1580111492, Solar heating, radiative cooling and thermal movement: Their effects on built-up roofing (United States. National Bureau of Standards. 0.1583 x 12 = 1.89 " of rise per foot of run. From the point you just marked, measure vertically straight up to the edge of the same sloping gable end trim or roof edge. © Copyright 2020 Hearst Communications, Inc. "Units" can be inches, feet, meters, furlongs, or hammer handle lengths. (roof slope < 2:12) single-ply roof system coverings installed in accordance with Sections 1507.12 and 1507.13 shall be ... not more than 6,000 square feet of projected roof area and where there is a minimum 10-foot fire-separation distance from the leading edge of the roof Then from that point on our level we measure the distance straight up to point of contact with the roof surface. slope as. This procedure to measure roof slope can be performed on the roof or from a ladder at roof edge. its attic) so we cannot make direct roof slope measurements, but we still need to know its slope? 6 in 12) gives us the vertical dimension of a right triangle. Roof rise (b): first we will obtain the total roof rise by counting siding courses. "A History of Innovation," http://www.owenscorning.com, 1997. This is EF. So you'd need 1,423 square feet of roofing. Mark this point on the leve. The minimum slope of horizontal branches shall be one-eighth unit vertical in 12 units horizontal (1-percent slope) unless otherwise approved. Roof pitch is given as the number of inches in height change over the distance of one foot. Tangent calculations are illustrated at ROOF SLOPE CALCULATIONS, Roof slope or pitch can also be expressed in degrees or angular degrees, as we illustrate at ROOF SLOPE DEFINITIONS, The numbers in the table above can be calculated as follows: (and as illustrated below). What size horizontal storm drain pipe should be installed for a building having 24,000 sq ft of projected roof area, where ¼ of the roof area will be serviced by a separate drain system in Albuquerque, New Mexico and the drain pipe is laid with 1/8"/ft slope? How to Calculate the Roof Area Using the Building Square Footage & the Pitch of the Roof. Determine rate of rainfall - for this example use 4". ft. 2. that's nearly straight up! 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