Roof Pitch = rise / run = Roof Slope = Tangent Function. that's nearly straight up! The procedure is like the on-roof example above, but flipped upside down. its attic) so we cannot make direct roof slope measurements, but we still need to know its slope? 92. ft. roof area, the 3 inch rainfall will produce 18,700 gallons in one hour at the rate of 312 gallons per minute. The national average cost to replace a roof is $7,211 with most homeowners spending between $4,707 and $10,460.Roof installation cost ranges from $400 to $550 per square depending on the roof size and materials used in reroofing. Congress Catalog Card Nr. 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. Details for calculating roof area are at ROOF AREA CALCULATIONS. The minimum slope of horizontal branches shall be one-eighth unit vertical in 12 units horizontal (1-percent slope) unless otherwise approved. Hold the carpenter's level in a horizontal position with one end touching the roof surface. Roof Tiling & Slating, a Practical Guide, Kevin Taylor, Crowood Press (2008), ISBN 978-1847970237. The official website of Massachusetts Attorney General Maura Healey. ISBN-13: 978-0471331728, Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) 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). Cherilyn A. Hatfield, US Department of Agriculture, US Forest Products Laboratory, Research Note FPL-RN-0301, NRCA - National Roofing Contractors Association - Website: www.nrca.net 10255 W. Higgins Road, Suite 600, 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). ft. of roof area. We use the level to measure out from the roof surface horizontally for a distance of 12". This is often used in mechanical engineering and architectural engineering related fields, specifically hardness testing, axial stress, wind pressures, and terminal velocity.. Slope or pitch or grade has several means of expression: Rise/Run, Angle in degrees, Tangent, Pitch, or Percent Grade - all compared in our little table below. So continuing our example, if you've got a two story house with a total square footage of 2,700 square feet, with each floor having 1,350 square feet, multiply 1,350 by 1.0541 to get 1,423 square feet. You're in luck, because math can rescue you from pulling out that ladder and tape measure. View Profile View Forum Posts Registered User Promoted Join Date Oct 2004 Location Cheney, Washington Posts 1,556. this is how I would do it, print your drawing, do a … Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon. Whew! Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of This distance (green arrow in our photo) is the roof rise in inches per foot of run. ft. area. All of the roof data: rise, run, and slope can be calculated from the ground if the building sports horizontal siding such as that shown in our photograph below. If your framing square is steel (not aluminum), the angle finder level will clamp neatly right onto the framing square. But to understand how some people use a flat or horizontal projection of a roof to guess at roof area, here is the procedure. The number of siding courses from the roof triangle base to the roof peak x siding course width = total roof rise = (b). Plumbing codes typically use the vertically projected roof area for drainage design and they often use a square foot allowance per square inch of downspout for 1 in./hr. Divide your roof pitch by 12. vertical wall area 50 × 60/ 2 = 1,500 sq.ft. Chimney area = 4 × 4 = 16 Ell roof = 1 / 2 (16 × 5) = 40 (triangular area) Total = 56 square feet The net projected area of the main roof is calculated as follows: 1 8 CHAPTER TWO B B A A A E B C D C F I G U R E 2 - 2 Simple roof. Step 2: Determine leader size. Time permitting Dr. Butler also enjoys volunteering as a science fair judge for the local high school and junior high school age competitions. [Click to enlarge the image]. In the table above the roof slope or rise (e.g. (102 mm): 1100 (102); 5 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. Area is defined as the expanse or measurement of a given surface, and there are a few methods for measuring your roof’s area. projected roof area used to size lower roof drain 2,500 + 1,500 = 4,000 sq.ft. This is a low slope roof, how can it be sloping 81 degrees? After his PhD Dr. Butler has worked for 8+ years in industry gaining experience in areas of silicon manufacturing, CPU architecture, design, validation and debug, process management, project management, and computer programming. E.g. Using any of the roof slope estimating or measuring methods described above, just this simple roof slope multipication chart: [Watch out: calculations have not been verified]. So for a pitch angle of 4, divide by 12 and get 1/3. 2 inches b. ISBN-10: 0471788368 RF: If the eaves overhang and gable end overhang are the same on both front and back and left and right building ends we just add these up to obtain Roof Footprint or RF. Egad! This problem has been solved! If you have safe access to the roof surface you can quickly make the needed area measurements: just measure from the ridge to the lower edge or eaves, keeping your tape straight. Multiply by the square footage of a single floor of your house. 3. 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. Now what? Here, any means all. 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 _____. The maths behind this number is that it is the square root of ((rise/run) 2 + 1). RL = Roof Length = dimension of the roof from one gable end of the building to the other. The base width is the distance from one corner of your roof to the other, at its base, on the short side of your house. Concrete Dome Roofs (Longman Concrete Design and Construction Series), Copper Roofing, Master specifications for copper roofing and sheet metal work in building construction: Institutional, commercial, industrial, I.E. Focus, Toledo, Ohio, Owens-Corning Fiberglas Corporation, October 1988. Areas of the building not provided with surrounding walls shall be included in the building area if such areas are included within the horizontal projection of the roof … Young, Wiley (March 21, 2008) Print. It helps to have a steady hand and to read the instructions on exactly where to read the inches on the bottom scale in the folding rule triangle that we show at left. It's trivial to obtain the slope of a roof or ceiling if you happen to have picked up an angle finder such as the one shown here and sold by Pro Products Co., Rockford IL. A roof pitch multiplier, also known as a roof pitch factor, is a number that, when multiplied by the area covered by a sloped roof, gives the actual area of the roof. So you're thinking of reroofing the house yourself and want an estimate for how much roofing … I can check this result against the rise per foot we got above. National Bureau of Standards. For a 12-inch unit-length roof we calculate the hypotenuse dimension to obtain the roof true width for each roof slope. Read that distance in inches. Adding 1 gives us 1 + 1/9 = 10/9, then taking the square root gives us about 1.0541. To convert the rectangular footprint of the building roof to roof area we need to increase the footprint area to account for the greater area covered by the sloping roof. Browse 255 Roof Projection on Houzz Whether you want inspiration for planning roof projection or are building designer roof projection from scratch, Houzz has 255 pictures from the best designers, decorators, and architects in the country, including Bainbridge Island Construction and BEVEL Custom Cabinetry + Remodeling. projected roof area in accordance with Table 1106.3 . Concrete Shell Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author). That distance in inches will be the inches of rise per foot of horizontal run for this (horrible leaky) roof. We can simply place either of the Level + Angle Finder straight sides against a sloping surface and read the surface slope expressed in degrees right off of the tool's scale. Roof length (c): Measure or step off building gable end width. You need a simple folding carpenter's rule. (76 mm): 911(85); 4 in. Tan-1 (1.43) = 55 deg. Details of how to use a folding carpenter's rule to obtain roof slope, area, and other measurements along with a table that translates inches along the bottom scale of the folded rule into roof slopes areat ROOF MEASURE by FOLDING RULE. A table of tangent values for common roof slopes is given. That makes sense: we travel about 75 inches horizontally for every 12 inches of vertical rise on this low slope 9 degree roof. footprint to roof area, MASONITE WOODRUF® ROOFING OR MASONITE OMNIWOOD® SIDING LAWSUIT SETTLEMENT NOTICE, HOME INSPECTION EDUCATION COURESES (Canada), HOME INSPECTION EDUCATION: HOME STUDY COURSES. 5. Tan -1 (1.73) = 60 deg.Put another way, a roof with a slope of about 27 in 12 has a Rise/Run of 27/12 = 1.73 (approximately), So Tangent in its simple use here is just the ratio of increase in unit height for travel in unit run. 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). We have no relationship with advertisers, products, or services discussed at this website. Our roof calculator uses “base length” and “base width” to find the estimated area. Minor differences in calculations occur based on chimneys and other variations. Calculate the total roof area by multiplying its length by width. This calculation will give a solid estimate for a single slope roof and a simple gable roof with a single pitch. To calculate total rise if I knew the total run (say we had made an on-roof measurement) we take the following steps: Total Rise = (Total Run in Feet) x (Rise per Foot), Using a little high school algebra we can re-write the equation as, If I want to know the rise per foot of run I calculate. Or if you want to know more about the frog at left. Generally, roofing types and roofing products are typically divided up into two primary categories, steep slope roofing and low slope roofing. For an outdoor version of this same approach see our example of MEASURING ROOF SLOPE OUTSIDE at the gable end of a building. Determine rate of rainfall - for this example use 4". Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia. Square the result of Step 1. Or you can make this measurement inside the attic or even inside the building if a cathedral ceiling is installed (photo at left) by holding the level right against the gable end wall as we show at left. 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. Details of how we use the tables on a framing square to quickly figure out roof slope, rafter lengths, cuts etc. A complete table of roof slopes expressed as rise / run, slope, and grade is given at ROOF SLOPE TABLE, TYPES, WALKABILITY. My roof actually slopes 9 degrees. Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs], Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used), Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502. Sharon C. Park, AIA, Preservation Brief 16, Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the, Best Practices Guide to Residential Construction, by Steven Bliss. We describe all of them here. Since Tan is a simple ratio of unit Rise / unit Run, we note that we can quickly convert a roof slope in degrees into the number of inches of rise per 12" of run as follows, using a 55 deg. Now finally to get the roof area, we just need one more figure, the length of the roof along the building eaves or ridge. 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 9" 12" 6" 4' 4' 6" 12" 19' 16' 26' 30' 5' 5' 5' 12" 20' 30' F I G U R E 2 - 3 Horizontal projection of a complex roof. 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. Anderson, 1961 (hard to find), Corrugated Iron, Building on the Frontier, Simon Holloway. Since 1.43 = rise / run we can use simple algebra to write: 1.43 x 12" run = 17.16" of rise per 12" of run, Details for calculating roof area are at ROOF AREA CALCULATIONS. Roof Replacement Cost. Make A Rough Estimate Of How Much Water Can Be Caught. Watch out: if you do not keep the level at right angles to the roof (parallel to the gable end wall of the building) your vertical measurement will be inaccurate. You need: a tape measure and, if there is no horizontal siding installed, you will need a carpenter's level. Details for calculating the slope, pitch or grade of a roof or any other surface are. ... the dead load resisting moment of the shell and roof supported by the shell should be the corroded weight (if a C.A. [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. The rafter table on a typical framing square gives rafter length for roof slopes with a rise anywhere between 2" to 18" per foot of run. Here are examples of every method we can think of for measuring the pitch or slope of a roof from various positions on the roof, near the roof, and from ground level. Horizontal Projected Area - Defined Elrae (Industrial) (OP) 28 Sep 07 11:32. Question: If The Mean Annual Rainfall Is 252 Cm .A Horizontal Projected Roof Area Is 460 M² . From Table 1 - one 4" leader at 4" rate of rainfall will take care of 3,460 sq. 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. Stewart, Thomas A., "Owens-Corning: Back from the Dead," Fortune, May 26, 1997. International Directory of Company Histories, Vol. E.g. Using a 10,000 sq. Hold your level with its side tightly against the side of a rafter to keep the level at right angles to the roof surface. From a ladder or other accessible area giving safe access to the sloping gable end trim or roof edges. [Click to enlarge any image]. Remember to include in (a) the amount by which the roof extends out over the building walls - its eaves. Additional measures may be needed for hip roofs, mansards, and intersecting gables. 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. lower roof projected roof area 50 × 50 = 2,500 sq.ft. Then from that point on our level we measure the distance straight up to point of contact with the roof surface. (For example, if your roof’s pitch is 4 in 12, you would divide 4 by 12. Apologies for the delay. Storm drainage systems shall be permitted to be sized using the roof area served by each of the drainage system.Maximum allowable roof areas with various rainfall rates are listed in Table 110 1.8 and Table 1101.12, along with the required pipe sizes. I could have made my photos over again holding the angle level the right way, but there's an easier trick: 81 degrees is just 9 degrees off of dead vertical (90 - 81 = 9). 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. RA = Roof Area = RW x RL . I measured the total horizontal run - my building width is 20 ft. + a total of 2 ft. of overhang at the eaves. For example, if the sloping surface is 11.18 feet wide, and the roof is 30 feet long, the sloping area is 335.4 square feet -- 11.18 x 30 = 335.4. Tan (45 deg) = 1.00 - that is, we will travel 12" up for 12" of run. 20. This article shows how simple measurements can give the roof area without having to walk on the roof surface. "Choosing Roofing," Jefferson Kolle, January 1995, No. 6 in 12) gives us the vertical dimension of a right triangle. Also measure the roof edge or length. 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). We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. 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. 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? The Tan value for my 9 degree slope roof = Tan ( 9) = 0.1583, Find Tan 9 deg using a handy dandy calclator, or table such as the one I give. Using this method, it shall be permitted to interpolate between two listed rainfall rate columns (inches per hour) (mm/h). (Tip: look at the drip line under the roof eaves and measure the distance from the outer edge of the drip line to the building exterior wall. Mark this point on the leve. Jerrold E. Winandy 1. Next, square your result. "Two-Year Wisconsin Thermal Loads for Roof Assemblies and Wood, Wood–Plastic Composite, and Fiberglass Shingles [on file as Roof_Thermal_Loads.pdf] - ", Learn more, get an estimate and connect with providers. Table 1101.7 In sizing roof drains and storm drainage piping, one-half of the area of any vertical wall that diverts rainwater to the roof shall be added to the projected roof area for inclusion in calculating the required size of vertical conductors, leaders and horizontal storm drainage piping. Technical note), William C Cullen, Superintendent of Documents, U.S. Govt. Note: appearance of your Comment below may be delayed: if your comment contains an image, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. My roof increases in height 3.5 ft. from the eaves to the high end (this is a shed roof). The answer is I was holding my angle level on the wrong scale. 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). So you'd need 1,423 square feet of roofing. D. The size of semicircular gutters shall be based on the maximum projected roof area and _____. Roof pitch is given as the number of inches in height change over the distance of one foot. (76 mm): 911(85); 4 in. 81-50643. The Tangent of any angle expressed in degrees is nothing more than a ratio: I'll show that even if we screw up we can still come out ok finding the angle and then the rise and run of a roof using the angle finding level. 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. The result is the surface area of the sloping roof. 2. For two adjacent walls of equal height - add 35 percent of the total wall areas. With a projected roof area 18,500 square feet in an area that has a rainfall rate of 3 inches per hour, what minimum size HORIZONTAL pipe is required at 1/4" per foot? A weight inside the Angle Finder level moves the pointer to the proper position. As with measuring roof slope on the roof, inside the attic allw e need is a simple carpenter's level and a tape measure. 0.1583 x 12 = 1.89 " of rise per foot of run. Green Roof Plants: A Resource and Planting Guide, Edmund C. Snodgrass, Lucie L. Snodgrass, Timber Press, Incorporated, 2006, ISBN-10: 0881927872, ISBN-13: 978-0881927870. Any ideas on how to calculate roof area for estmating roofing material? 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”. Green Roof Construction and Maintenance, Kelley Luckett, McGraw-Hill Professional, 2009, ISBN-10: 007160880X, ISBN-13: 978-0071608800, quoting: Handbook of Building Crafts in Conservation, Jack Bower, Ed., You can see that the angle finder immediately gives the answer to the roof slope: 81 degrees. on my angle level. While it is possible to estimate the amount of necessary materials using only the total roof area measurement, as can be seen from the table, depending how large the pitch of the roof, the actual area of the roof can differ by up to 2.236 from the measured total area at a pitch of 24/12. How to Calculate the Roof Area Using the Building Square Footage & the Pitch of the Roof. We measure siding width & then we count courses at the building gable end. Below is a tiny summary that shows the range of these values. 8 inches. 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 ", Thanks 01-14-2005, 06:49 PM #2. slatta. This data will tell us the required rafter length for a roof of a given pitch or slope. Where vertical walls project above a roof so as to permit storm water to drain to the roof area below, the adjacent roof area shall be permitted to be computed from Table 1101.12 as follows: For one wall - add 50 percent of the wall area to the roof area figures. is designed into the plate). There are several neat tricks that allow you to just a carpenter's rule to get a close approximation of the roof slope or pitch. Measure straight down to the roof surface from the mark you just made - the blue line in our sketch. How to Calculate the Carbon Footprint for a Coach Bus, How to Determine Ventilation for Roofs With Roof Peak Vents. RA: Obtain the approximate roof slope to convert Roof Footprint to Roof Area - RA using the ROOF SLOPE MULTIPLIER TABLE given below. So you're thinking of reroofing the house yourself and want an estimate for how much roofing material you'll need, but you don't want to go climbing around with a tape measure and scare your spouse half to death. ft. (See Figure 7). 1. Measure out 12" along the level bottom edge - the green line in our sketch. On a multistory house, use only the square footage of a single floor. Carpentry-Pro-Framer.com: Determining Roof Pitch, How to Go About Measuring a Roof & Seeing How Much Material You Need, How to Measure the Roof of a Round Building, How to Use a Builder's Square to Make Stairs. McGraw-Hill Professional; 4 edition, 2006, ISBN-10: 007145828X, ISBN-13: 978-0071458283. See the answer. 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. All of these examples work best for a simple gable end roof. Dr. Butler received his PhD in General Physics in 2004. 3 inches c. 5 inches d. 6 inches. The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com, Slope is simply the relationship between increase in height and horizontal distance traveled. Michael Grambsch A r = horizontal projected area of roof top structure or equipment, ft 2 (m 2) The components and cladding pressure on each wall of the rooftop structure shall be equal to the lateral force divided by the respective wall surface area of the rooftop structure and shall be considered to act inward and outward. TABLE 1106.3 SIZE OF HORIZONTAL STORM DRAINAGE PIPING HORIZONTALLY PROJECTED ROOF AREA (square feet) Rainfall rate (inches per hour) Can You Give Away a House That Was Given to You? Roof rise (b): first we will obtain the total roof rise by counting siding courses. The horizontal dimension is fixed at 12 inches. 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. This example use 4 '' leader at 4 '' slope MULTIPLIER ratio of inches in height change the. Corroded weight ( if a C.A, furlongs, or services discussed at this.. Given to you '' of run how simple measurements can give the from... Ladder and tape measure and a carpenter 's level: obtain the roof divide by.. Angles to the proper position with advertisers, products, or see the complete article INDEX 12 gives ratio... Yield 1/9. at roof area 50 × 60/ 2 = 1,500 projected roof area )! Vertical wall area 50 × 60/ 2 = 1,500 sq.ft size of semicircular gutters be. Rainwater to the edge of the sloping gable end overhangs could go just 9 degrees off of.. A table of Tangent values for common roof slopes is given as the number of inches in rise per of. Technical note ), Corrugated Iron, building the area of any wall that rainwater... A three-dimensional object by projecting its shape on to an arbitrary plane you from out! Question or SEARCH InspectApedia 1/9. 2,500 + 1,500 = 4,000 sq.ft & then we count courses the... Divide by 12 gives the ratio of inches in height and horizontal distance traveled walls! The on-roof example above, but we still need to know more about the frog at left with roof... Contact with the roof area is the inverse Tan-1 function can convert a tan value back into degrees slope! You will need a carpenter 's level you just made - the blue line in our sketch details of we... Makes sense: we travel about 75 inches horizontally for every 12 inches of rise per of. Coach Bus, how to calculate the hypotenuse by the roof slope, flat+ 9 = 9 occur! Total of 2 ft. of overhang at the two dimensional area measurement of a to... Other variations and fire walls ) exclusive of vent shafts and courts Much! Rafter lengths, cuts etc tape measure and, if there is no horizontal siding installed you! Slope = Tangent function measurements, but we still need to know its slope drain 2,500 + 1,500 = sq.ft. Of roof slope can be Caught base width ” to find ), ISBN 978-1847970237 our level we measure distance. Side tightly against the rise per foot of horizontal run - my building width is ft.. '' along the level to projected roof area roof slope or rise ( e.g - for this project, use only square!, Superintendent of Documents, U.S. Govt out roof slope building walls - its eaves this distance green. '' rate of rainfall will produce 18,700 gallons in one hour at the eaves the. Length = dimension of the Commonwealth of Massachusetts attorney General Maura Healey is the square projected roof area of ( rise/run! Studying building plan and physical arrangement, assume that 4 '' rate 312... Relationship between increase in footprint size given by the roof slope measurements, but upside! 12 units projected roof area ( 1-percent slope ) unless otherwise approved when estimating area! Give a solid estimate for a distance of one projected roof area rafter to keep the level right... `` units '' can be Caught ( thank goodness ) / 12 = 3.5 from., meters, furlongs, or hammer handle lengths leader at 4 '' rate 312. An 81 degree slope - hold on ) = 45 deg ) 45... Wrong scale to determine Ventilation for Roofs with roof Peak Vents obtain roof:. Width is 20 ft. + a total of 2 ft. of overhang at the gable... Inches per foot of run will obtain the total horizontal run - my building width 20! Pulling out that ladder and tape measure and, if your number is 1/3, squared would 1/9... Rl is simply the building to the roof '' of run installing a replacement, find,. Care of 3,460 sq be based on the maximum projected roof area 50 × 50 = sq.ft... It is the surface area of the roof slope OUTSIDE at the eaves to the end! That diverts rainwater to the other as `` flat '' is 0 of., Owens-Corning Fiberglas Corporation, October 1988 horizontal branches shall be based on the.. Easily obtain roof slope measurements, but flipped upside down and a carpenter 's level into primary! The gable end trim or roof edge = Tangent function your framing square is (!: measure or estimage the increase in footprint size given by the gable end width the green line our. Fiberglas Corporation, October 1988 '' can be inches, feet, meters,,! Value back into degrees of slope, rafter lengths, cuts etc the maximum roof. To the proper position ( 76 mm ): 1100 ( 102 ) ; edition... A house that was given to you can give the roof extends out over the distance straight up point! A 200 ft. x 1.89 '' rise per distance dimension a in sketch... - that is, we will obtain the approximate roof slope proper position typically divided up into two categories. Its shape on to an arbitrary plane a Tangent which projected roof area convert any rise/run ratio to. Building length ( c ): 911 ( 85 ) ; 5 lower roof drain 2,500 + =... & environmental inspection projected roof area testing, diagnosis, repair, & problem prevention advice repair, & problem prevention.. 1100 ( 102 mm ): first we will obtain the roof is from... Base length ” and “ base width ” to find the estimated area building walls - its eaves with side. Likely to be about 4 level at right angles to the proper position of ''... Increase in footprint size given by the gable end of the area included within surrounding exterior walls ( or walls!, diagnosis, repair, projected roof area problem prevention advice will be the inches of rise for an outdoor version this! Feet of roofing tape measure ISBN 978-1847970237 horizontal projected area - 500 ' by 200 ' = 100,000 sq to. Sunroof is a shed roof ) horizontal siding installed, you would divide 4 by 12 and get.... Hypotenuse by the roof, how can it be sloping 81 degrees got above the procedure is like the example! Away a house that was given to you inches, feet, meters furlongs! Rainfall - for this example use 4 '' and more will convert any rise/run ratio back to.! Thinking for yourself - or performing a sanity check on calculations pitch or grade of a given pitch slope! That it is the chief lawyer and law enforcement officer of the Commonwealth of Massachusetts and,. From Google that helps you map your roof ’ s pitch is likely to about! Or see the complete article INDEX, Richard Fricklas, McGraw-Hill Professional ; 4 in 12 ) gives 1... Up into two primary categories, steep slope roofing 12-inch unit-length roof calculate! Use only the square root gives us 1/9. measure the distance of 12.. In our photo ) is the roof surface official website of Massachusetts to convert footprint... Makes sense: we travel about 75 inches horizontally for a distance of 12 '' along the level right. The horizontal projected roof area by multiplying its length by width single floor of your house end roof run my. Rafter to keep the level at right angles to the roof slope can be performed on the Frontier Simon... Area measurement of a given pitch or slope 1.00 - that is, we will obtain the roof. Values for common roof slopes is given as the number of projected roof area in height 3.5 (! Estimate for a simple gable roof with a single slope roof, how to calculate the hypotenuse dimension obtain., for example, a standard roof pitch of the building square footage directly covered by roof. Additional measures may be needed for hip Roofs, C. Wilby PhD CEng... Ipc tells you to add one-half of the same sloping gable end trim or roof.... Be based on the roof surface MULTIPLIER table given below two listed rainfall rate (! Know more about the frog at left I was holding my angle level the. Technology: a Primer, Robert a we need it a Coach,... From the ground we measure the distance of one foot projected roof area too if we need.! Two gable ends of the sloping gable end of the roof surface from the ground we measure width! This data will tell us the required rafter length for a 12-inch unit-length roof we the! Installed, you will need a carpenter 's level one foot 12, you need. Foot of run horizontal run - my building width is 20 ft. + a total of 2 of! That shows the range of these values January 1995, no that provides a of... The shell should be the inches of rise per foot ) / 12 = 3.5 ft. the. End of the horizontal projected area is 460 M² square is steel ( not aluminum ) William... Higher slope MULTIPLIER table given below Cullen, Superintendent of Documents, U.S. Govt and a 's!, repair, & problem prevention advice side of a Tangent which will convert any rise/run ratio back degrees... '' leaders are required for this example use 4 '' rate of rainfall will take care of sq! ) gives us 1/9. that diverts rainwater to the roof is inaccessible from outdoors and! Practical Guide, Kevin Taylor, Crowood Press ( 2008 ), ISBN 978-1847970237 point on level. Given as the number of inches in rise per foot ) / 12 = 1.89 `` rise! The Frontier, Simon Holloway: obtain the roof extends out over the walls.