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The High Velocity Hurricane Zone Roof Drainage Requirements

2. Why is roof drainage so important?. Roofs are typically designed for a 30 psf. live load.*One square foot of water, one inch deep, weighs 5.2 lbs.The maximum depth of water allowed by Code is 5", weighing 26 lbs./ft.2.It would take only one hour at the design rainfall rate for 5" to accumulate. There are 3000 roof collapses a year in the USA, many because of inadequate drainage..

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The High Velocity Hurricane Zone Roof Drainage Requirements

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    1. The High Velocity Hurricane Zone Roof Drainage Requirements PRESENTED BY THE OFFICE OF BUILDING CODE COMPLIANCE

    2. 2 Why is roof drainage so important? Roofs are typically designed for a 30 psf. live load.* One square foot of water, one inch deep, weighs 5.2 lbs. The maximum depth of water allowed by Code is 5”, weighing 26 lbs./ft.2. It would take only one hour at the design rainfall rate for 5” to accumulate. There are 3000 roof collapses a year in the USA, many because of inadequate drainage. HVHZ.1615.1 Minimum roof live loads. Roofs shall be designed for a live load of not less than 30 pounds per square foot (1436 Pa), except as set forth herein. EXCEPTIONS. 1. Glass areas of greenhouse roofs shall be designed for a live load of not less than 15 pounds per square foot (718 Pa). 2. Ordinary pitched and curved roofs, with a slope of 1-1/2:12, or greater, where water is not directed to the interior of the roof, without parapet or other edge of roof drainage obstructions, may be designed for an allowable live load of not less than 20 pounds per square foot (958 Pa). HVHZ.1615.1 Minimum roof live loads. Roofs shall be designed for a live load of not less than 30 pounds per square foot (1436 Pa), except as set forth herein. EXCEPTIONS. 1. Glass areas of greenhouse roofs shall be designed for a live load of not less than 15 pounds per square foot (718 Pa). 2. Ordinary pitched and curved roofs, with a slope of 1-1/2:12, or greater, where water is not directed to the interior of the roof, without parapet or other edge of roof drainage obstructions, may be designed for an allowable live load of not less than 20 pounds per square foot (958 Pa).

    3. 3 Roof Slopes A roof with a slope of 1:240 is considered the same as a dead-level roof for a roof to be considered to have a positive slope it must have a slope of more than 1:240. The Florida Building Code Requires a slope of 1:48 or a ¼” per foot.* This is done to preclude ponding instability. The following section of the code does not apply to Miami-Dade or Broward Counties. Sections 1501 thru 1510 do not apply to Miami Dade or Broward only Sections 1511 thru 1525 Apply to the High Velocity Hurricane Zone. §1508.3.1 Slope. Built-up roofs shall have a design slope of a minimum of 1/4:12 for drainage, except for coal-tar built-up roofs that shall have a design slope of a minimum of 1/8:12. It has been quoted by some persons in presentations in Miami-Dade County 1:240 is about 3/64” per foot The following section of the code does not apply to Miami-Dade or Broward Counties. Sections 1501 thru 1510 do not apply to Miami Dade or Broward only Sections 1511 thru 1525 Apply to the High Velocity Hurricane Zone. §1508.3.1 Slope. Built-up roofs shall have a design slope of a minimum of 1/4:12 for drainage, except for coal-tar built-up roofs that shall have a design slope of a minimum of 1/8:12. It has been quoted by some persons in presentations in Miami-Dade County 1:240 is about 3/64” per foot

    4. 4 SECTION 1515 HIGH VELOCITY HURRICANE ZONES - PERFORMANCE REQUIREMENTS §1515.2.2.1 All roofing systems must be installed to assure drainage. In new construction the minimum deck slope shall be not less than 1/4:12.

    5. 5 Ponding Instability Ponding instability is a phenomenon that occurs anytime that water accumulates on a roof. When water accumulates on a roof the roof deflects under the weight of the water consequently, more water ponds and the more water that ponds the more it deflects and continues to compound itself until failure occurs or the situation is remedied.

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    12. 12 Properties of water Water weighs 8.33 lbs./gal. There are 231 in.3 in one gallon. There are 7.48 gallons in a cubic foot. A cubic foot of water weighs 62.4 lbs. A rainfall of 1 gpm = 8.02 ft.3/hr 8.33 x 7.48 =62.3084 8.33 x 7.48 =62.3084

    13. 13 Where do we find drainage information in the FBC? Chapter 15, Building Volume HVHZ 1514.4* Chapter 16, Building Volume HVHZ 1614.1 Chapter 11, Plumbing Volume P1102.3 ASCE 7-98 Chapter 8 Code of Miami-Dade County Drainage design requires the coordination of the Architect, Structural Engineer and Plumbing Engineer. §1514.4 Roof Drainage. Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof. Where required for roof drainage, scuppers shall be placed level with the roof surface in a wall or parapet. The scupper shall be located as determined by the roof slope and contributing roof area. §1614.1 Live loads. Minimum uniformly distributed live loads shall not be less than as set forth in and Table 4-1 of ASCE 7 with Commentary, except as otherwise noted in this code. Chapter 8 of Miami-Dade County requires drawings to be submitted for roofing. §1514.4 Roof Drainage. Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof. Where required for roof drainage, scuppers shall be placed level with the roof surface in a wall or parapet. The scupper shall be located as determined by the roof slope and contributing roof area. §1614.1 Live loads. Minimum uniformly distributed live loads shall not be less than as set forth in and Table 4-1 of ASCE 7 with Commentary, except as otherwise noted in this code. Chapter 8 of Miami-Dade County requires drawings to be submitted for roofing.

    14. 14 Building (Changed) HIGH VELOCITY HURRICANE ZONES - GENERAL §1611.1.7 In any conflict between ASCE 7 with commentary and this code, the more stringent requirement shall apply. 1612.1.3 No building structure or part thereof shall be designed for live loads less than those specified in this chapter or ASCE-7 with commentary, except as otherwise noted in this code. ASCE-7 1998 is where the table that establishes how much head of water is required to make a drain or pipe drain a certain amount of water. Because water when trickling over the edge of a roof drain does not drain at the same rate as water which has risen to 2” above the edge of the drain. Gravity and head have an effect on how much water a given roof drain will drain. ASCE-7 1998 is where the table that establishes how much head of water is required to make a drain or pipe drain a certain amount of water. Because water when trickling over the edge of a roof drain does not drain at the same rate as water which has risen to 2” above the edge of the drain. Gravity and head have an effect on how much water a given roof drain will drain.

    15. 15 HVHZ §1514.4.2 Overflow drains and scuppers. Where roof drains are required, overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches (51 mm) above the low point of the roof, overflow scuppers shall be a minimum of 4 inches (102mm) in height and shall be placed in walls or parapets with the inlet flow line not less than 2 inches (51mm) above the roof surface, excluding sumps, or more than 4 inches (102 mm) above the roof surface and shall be located as close as practical to required vertical leaders or downspouts or wall and parapet scuppers. Overflow drains and scuppers shall also comply with the Florida Building Code, Plumbing, and §1616 of this code.* This is in direct conflict with 1107.3 Plumbing which tells you that scuppers have to be 3 times the area of the primary drains and that overflow drains have to be sized by table 1106.3 but with the values divided by two. Consequently this results in a larger drain. See next slide. This section also tells us that the overflow scupper has to be installed with the inlet flow line 2 inches above the low point of the roof. This is also in error. The overflow scupper has to be installed at a point were it is above the hydraulic head necessary to make the drain accept the gpm. In question. For instance a roof 3000 sq. ft may be accommodated with a single 4” drain but said drain will need will produce 156 gpm. This will require approximately 1 ¾” of head. With this in mind you have to provide some separation between the primary and the secondary if you make that one inch you have now used 2 ¾” of the given 5” max that you are allow to accumulate on the roof. Meaning the scupper has to be locate 2 3/4” of the deck and it has to do its work in the 2 ¼” left from the give 5”.This is in direct conflict with 1107.3 Plumbing which tells you that scuppers have to be 3 times the area of the primary drains and that overflow drains have to be sized by table 1106.3 but with the values divided by two. Consequently this results in a larger drain. See next slide. This section also tells us that the overflow scupper has to be installed with the inlet flow line 2 inches above the low point of the roof. This is also in error. The overflow scupper has to be installed at a point were it is above the hydraulic head necessary to make the drain accept the gpm. In question. For instance a roof 3000 sq. ft may be accommodated with a single 4” drain but said drain will need will produce 156 gpm. This will require approximately 1 ¾” of head. With this in mind you have to provide some separation between the primary and the secondary if you make that one inch you have now used 2 ¾” of the given 5” max that you are allow to accumulate on the roof. Meaning the scupper has to be locate 2 3/4” of the deck and it has to do its work in the 2 ¼” left from the give 5”.

    16. 16 Florida Building Code Plumbing P1107.3 Sizing of secondary drains. Secondary (emergency) roof drain systems shall be sized in accordance with §P1106 based on the rainfall rate for which the primary system is sized but with the sizing adjusted by dividing the values for horizontally projected roof area in Table P1106.2, Table P1106.3 and Table P1106.6 by two. The minimum cross-sectional area of an overflow scupper shall be three times the cross-sectional area of the primary roof drain and the scupper shall have a minimum opening dimension of 4 inches (102 mm). The flow through the primary system shall not be considered when sizing the secondary roof drain system.

    17. 17 Florida Building Code Plumbing (new) 1107.3 Sizing of secondary drains. Secondary (emergency) roof drain systems shall be sized in accordance with Section 1106 based on the rainfall rate for which the primary system is sized in Tables 1106.2, 1106.3 and 1106.6. Scuppers shall be sized to prevent the depth of ponding water from exceeding that for which the roof was designed as determined by Section 1101.7. Scuppers shall not have an opening dimension of less than 4 inches (102 mm). The flow through the primary system shall not be considered when sizing the secondary roof drain system.

    18. 18 When are roof drains required? Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof. (HVHZ 1514.4) “Drains or scuppers installed to provide overflow drainage shall be not less in aggregate area than as shown in Figure 1616.3, but not less than 4 inches (102 mm) dimension in any direction and shall be placed in parapets not less than 2 inches (51 mm) nor more than 4 inches (102 mm) above the roof deck” (HVHZ 1616.3)* All roof systems must be installed to assure drainage. (HVHZ 1515.2.2.1) In new construction the minimum deck slope shall be ¼ : 12. (HVHZ 1515.2.2.1) Primary drains are to be sized per Table P1106.2. How can you install a drain 2” above the roof deck this should only apply to scuppers How can you install a drain 2” above the roof deck this should only apply to scuppers

    19. 19 Could a Scupper be Used as a Primary Roof Drain? Where required for roof drainage, scuppers shall be placed level with the roof surface in a wall or parapet. (HVHZ 1514.4)* The scupper shall be located as determined by the roof slope and contributing roof area. (HVHZ 1514.4) Parapet wall roof drainage scupper location shall comply with the FBC Building Volume. Plumbing (1106.5) HVHZ Roof Drainage 1616.2 Where roofs are not designed in accordance with 1616.1, overflow drains or scuppers shall be placed to prevent an accumulation of more than 5 inches (927 mm) of water on any portion of the roof. In determining the load that could result should the primary drainage system be blocked, the loads caused by the depth of water (i.e., head) needed to cause the water to flow out the scuppers or secondary drainage system shall be included. The 2005 version of the FBC is going to have a table to size scuppers for primary drainage in Chapter 11 of the Plumbing Code. (Table 1106.7)HVHZ Roof Drainage 1616.2 Where roofs are not designed in accordance with 1616.1, overflow drains or scuppers shall be placed to prevent an accumulation of more than 5 inches (927 mm) of water on any portion of the roof. In determining the load that could result should the primary drainage system be blocked, the loads caused by the depth of water (i.e., head) needed to cause the water to flow out the scuppers or secondary drainage system shall be included. The 2005 version of the FBC is going to have a table to size scuppers for primary drainage in Chapter 11 of the Plumbing Code. (Table 1106.7)

    20. 20 Using a Scupper as a Primary Drain When using a scupper as a primary means of roof drainage care must be exercised to direct the water away from the building. The Code does not allow water to be drained less than a foot from the wall of the building. §1503.4.4 Protection against decay and termites. Condensate lines and roof downspouts shall discharge at least 1 foot (305 mm) away from the structure sidewall, whether by underground piping, tail extensions, or splash blocks. Gutters with downspouts are required on all buildings with eaves of less than 6 inches (152 mm) horizontal projection except for gable end rakes or on a roof above another roof. §1503.4.4 Protection against decay and termites. Condensate lines and roof downspouts shall discharge at least 1 foot (305 mm) away from the structure sidewall, whether by underground piping, tail extensions, or splash blocks. Gutters with downspouts are required on all buildings with eaves of less than 6 inches (152 mm) horizontal projection except for gable end rakes or on a roof above another roof.

    21. 21 When is secondary or overflow drainage required? When roof drains are required. (HVHZ 1514.4.2) When roof perimeter construction extends above the roof, where water would be trapped if the primary drains allow build-up for any reason. (P1107.1) When parapets or curbs are constructed, water build-up in excess of that considered in the design shall be prevented. (HVHZ 1616.1) It is also acceptable to design the roof for a higher load. For instance there are local engineers that routinely design for 100 pounds per square foot.It is also acceptable to design the roof for a higher load. For instance there are local engineers that routinely design for 100 pounds per square foot.

    22. 22 Structural Concerns No accumulation in excess of that considered in the design. (HVHZ 1616.1) No more than 5” of water accumulation when not designed per 1616.1. (HVHZ 1616.2) Depth caused by hydraulic head needed to cause flow through the secondary drain shall be included in determining the load. (HVHZ 1616.2) All roofs shall be designed with sufficient slope or camber. (HVHZ 1614.4) We will show you how to find the amount of water that falls on a roof in gallons per minute and will show you how to find the hydraulic head needed to make a roof drain get rid of the required gpm. We will show you how to find the amount of water that falls on a roof in gallons per minute and will show you how to find the hydraulic head needed to make a roof drain get rid of the required gpm.

    23. 23 What is Hydraulic Head? Is the amount of head needed to cause water to flow out of a drain or a scupper at a set rate. Example for a 4” roof drain to be able to drain 170 Gals. Per minute it must have 2” of head over the drain. With 1” of head it will only drain 80 G.P.M

    24. 24 How do you size a primary drain First establish the projected horizontal area of the roof (square footage) including any vertical wall that drains unto the roof (do not include parapets) Next establish the rate of rainfall. 4.7” for Miami-Dade. Size as per Table 1106.2 of the Plumbing Code.

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    27. 27 Example #1 With this information go to Figure 1106.1 Chapter 11 of the Plumbing Code. Or go to Appendix “B” Rates of rainfall for various cities . Here you will determine that the rate for Miami –Dade is 4.7”. The commentary tells us that we should go to the next higher number in the table, in this case 5”

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    37. 37 Roof Drainage 130 gals per minute on a 4” drain you may interpolate and obtain about 1 ¾” hydraulic head. This means that at its design capacity there is going to be 1 ¾” of water over the drain, this is fine since the code requires the roof to be designed in a way that the maximum amount of water that can accumulate is less than 5”. This means that the secondary drain has to be placed a minimum of 1 ¾” above the roof. * In my opinion 1” above the amount of head required to cause the drain to drain the 130 gals. per minute would adequate but the code may require 2” (look at 1514.4.2). In this case if the secondary is placed at 2”. The reason for placing the secondary at this height is to avoid the secondary working during a normal design rainfall. The secondary is required to act as an alarm when water is seen coming out of the secondary system its saying “THERE IS A PROBLEM ON THE ROOF” §1514.4.2 Overflow drains and scuppers. Where roof drains are required, overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches (51 mm) above the low point of the roof, overflow scuppers shall be a minimum of 4 inches (102mm) in height and shall be placed in walls or parapets with the inlet flow line not less than 2 inches (51mm) above the roof surface, excluding sumps, or more than 4 inches (102 mm) above the roof surface and shall be located as close as practical to required vertical leaders or downspouts or wall and parapet scuppers. Overflow drains and scuppers shall also comply with the Florida Building Code, Plumbing, and §1616 of this code.* In my opinion 1” above the amount of head required to cause the drain to drain the 130 gals. per minute would adequate but the code may require 2” (look at 1514.4.2). In this case if the secondary is placed at 2”. The reason for placing the secondary at this height is to avoid the secondary working during a normal design rainfall. The secondary is required to act as an alarm when water is seen coming out of the secondary system its saying “THERE IS A PROBLEM ON THE ROOF” §1514.4.2 Overflow drains and scuppers. Where roof drains are required, overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches (51 mm) above the low point of the roof, overflow scuppers shall be a minimum of 4 inches (102mm) in height and shall be placed in walls or parapets with the inlet flow line not less than 2 inches (51mm) above the roof surface, excluding sumps, or more than 4 inches (102 mm) above the roof surface and shall be located as close as practical to required vertical leaders or downspouts or wall and parapet scuppers. Overflow drains and scuppers shall also comply with the Florida Building Code, Plumbing, and §1616 of this code.*

    38. 38 Why the concern with hydraulic head? §1616.2 Where roofs are not designed in accordance with §1616.1, overflow drains or scuppers shall be placed to prevent an accumulation of more than 5 inches (927 mm) of water on any portion of the roof. In determining the load that could result should the primary drainage system be blocked, the loads caused by the depth of water (i.e., head) needed to cause the water to flow out the scuppers or secondary drainage system shall be included.* This is hydraulic head. The loads caused by the depth of water needed to cause water to flow out the scuppers or secondary drainage system shall be included. This means that the hydraulic head has got to be taken into consideration when designing the roofs and drainage systems. This is hydraulic head. The loads caused by the depth of water needed to cause water to flow out the scuppers or secondary drainage system shall be included. This means that the hydraulic head has got to be taken into consideration when designing the roofs and drainage systems.

    39. 39 When is secondary or overflow drainage required? When roof drains are required. (1514.4.2) When roof perimeter construction extends above the roof, where water would be trapped if the primary drains allow build-up for any reason. (1107.1) When parapets or curbs are constructed, water build-up in excess of that considered in the design shall be prevented. (1616.1) Don’t forget that to use scuppers as a means of secondary drainage on a roof that has roof drains as the means for primary drainage you are limited in distance from low point in roof to scupper. About 12 feet on account of the ¼” per foot. Don’t forget that to use scuppers as a means of secondary drainage on a roof that has roof drains as the means for primary drainage you are limited in distance from low point in roof to scupper. About 12 feet on account of the ¼” per foot.

    40. 40 Roof Drainage The code requires that the secondary drainage has to be sized using table 1106.2 and dividing the values by two.* 1107.3 Sizing of secondary drains. Secondary (emergency) roof drain systems shall be sized in accordance with Section 1106 based on the rainfall rate for which the primary system is sized but with the sizing adjusted by dividing the values for horizontally projected roof area in Tables 1106.2, 1106.3 and 1106.6 by two. The minimum cross-sectional area of an over-flow scupper shall be three times the cross-sectional area of the primary roof drain and the scupper shall have a minimum opening dimension of 4 inches (102 mm). The flow through the primary system shall not be considered when sizing the secondary roof drain system. In the new code coming out n July 2005 this requirement is taken out. But since the rest of the code remains unchanged all is going to do is create confusion. Even under the present code there are instances when you size the secondary by dividing the values in the table by two and you end up with more than 5” of water on the roof. This is why is so important to always do calculations and not follow the tables blindly.In the new code coming out n July 2005 this requirement is taken out. But since the rest of the code remains unchanged all is going to do is create confusion. Even under the present code there are instances when you size the secondary by dividing the values in the table by two and you end up with more than 5” of water on the roof. This is why is so important to always do calculations and not follow the tables blindly.

    42. 42 Roof Drainage The head over the primary has been established at 1 ¾”, 130 gals per min on a 5” drain would give us 1 ½” of hydraulic head. Place the secondary at 2” above the deck with 1 ½” of hydraulic head this would give us a maximum of 3 ½” of water on the roof even if the primary were to become clogged. There are drains that have a dam built in, or the drain can placed at a location were the 2” above the low point in the deck happens to be on deck.

    44. Example #2, roof slopes at ¼ in./ft. to a single interior drain.

    45. 45 Size the primary drain for example roof #2. Roof area 90’ x 85’ = 7650 ft.2 Rainfall rate for Miami =5” Read down the 5” rainfall column of Table 1106.2 until a projected roof area figure that is equal to or greater than the sample roof area is found. Then read across the Table to find the required drain size. A 6” drain is found to be required.

    47. 47 Establish the hydraulic head at the primary drain for example roof #2 To establish rainfall in gallons per minute. Multiply square footage, times the Miami rainfall rate, then multiply times the conversion factor. 7650 x 5 x 0.0104 = 398 gal/min. Refer to ASCE 7-98 Table C8-1. Hydraulic head for a 6” drain, that must drain 398 gal/min., falls between 3” and 3.5”. Interpolation is necessary to establish an exact hydraulic head.

    48. Establishing hydraulic head above the primary drain

    49. 49 Could overflow scuppers be used to provide secondary drainage? The easy way to figure this is to just divide the distance from the primary to the parapet by 4 to obtain the height of water at the primary. In this case divide 42.5’ ÷ 4 = 10.6” consequently you could not use a scupper as a means of secondary drainage. You would have 10.6” of water on the roof before it reached the scupper.

    50. 50 Secondary Drain Piping must be separate. Why? (1107.2)* Secondary must discharge above grade. Why? (1107.2) Discharge must be in a location where it would be normally observed. Why? (1107.2) Height placement of the invert of the secondary drain must be above the depth of water of the primary drain at its design flow. This requirement seems to be implied by the Code, though not explicit. §P1107.2 Separate systems required. Secondary roof drain systems shall have piping and point of discharge separate from the primary system. Discharge shall be above grade in a location which would normally be observed by the building occupants or maintenance personnel. §P1107.2 Separate systems required. Secondary roof drain systems shall have piping and point of discharge separate from the primary system. Discharge shall be above grade in a location which would normally be observed by the building occupants or maintenance personnel.

    51. 51 A secondary drain will be required, how is it sized? The projected roof areas shown in Table 1106.2 must be divided by two. Then read down the 5” rainfall column until a figure equal to or greater than the projected roof area is found. Projected roof area 7650 ft.2

    53. 53 Establish the hydraulic head above the secondary drain For an 8” secondary drain the head falls between 2.5”-3”. 2.5” +[( 398-340 ÷ 560-340) x .5] = hd 2.5” + [(58 ÷ 220) x .5] = hd 2.5” + 0.1318 = 2.63” If the primary drain could not handle the peak flow for any reason, the secondary would accommodate the design flow. At the design rainfall rate, there would be a depth of water 2.6” above the secondary drain.

    55. Alternate method

    56. 56 Are the structural rain load requirements of the Code met? Depth above the primary = 3.06” Placement of the invert of the secondary = 4” above the low point. Depth above the secondary = 2.6” 3.06” + .94” + 2.6” = 6.6” This depth of water exceeds maximum 5” load allowed by the Code. Even if the secondary was placed with the invert at the point of the hydraulic head of the primary you still have 5.66” of water on the roof. Even though the plumbing requirements are met, the structural requirements are not.

    58. 58 Options Go to a bigger primary. Go to a bigger secondary. Or both. Or design the structure to withstand this rain load.

    61. 61 Formulas To obtain the gallons per minute that fall on a given roof at the rate for Miami-Dade County (5” per hour). There is 144 cubic inches in a section of roof 12” x 12” x 1”. There is 231 cubic inches in a gallon. If you divide 144 by 231 you obtain accumulation of rainfall in gals. per hour per sq. ft. To obtain gals. Per minute divide the result by 60 144 ÷ 231 ÷ 60 =.0104 Square feet of roof x 5” x .0104 = gpm falling on the roof.

    62. 62 Formulas Formula to calculate amount ponding water on the roof: V = 4p x W x L x D 3 2 2 2 V= Cubic Feet W= Width L= Length D= Depth Depth must be expressed in feet or decimal of feet

    63. 63 Formulas Francis Formula: Q =3.33 (b-0.2H)H1.5 b = scupper with in feet Q = Flow in Cu. Ft. per Sec. H = Hydraulic head in feet (or height of scupper)

    64. 64 Formulas Factory Mutual Formula for Flow: Q = 2.9 b(H)1.5 Q = Flow in gallons per minute b = Base or in this case width of scupper H = Hydraulic head or height of scupper

    65. 65 Estimating Weight of Ponded Roof Water V = 4p x W x L x D 3 2 2 2 Example; A pond 70’ long by 40’ wide and 7/8”deep at the center: V= 4 x 3.14 ¸ 3 x 40 ¸ 2 x 70 ¸ 2 x (7/8” ¸12) = 2 4.18 x 20 x 35 x .0364 = 106.67 Cu. Ft. = V V= 106.67 Cu. Ft. x 62.4 = 6656.65 lbs ¸ 2000 = 3.3 Tons

    68. 68 THE END

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