|
SYSTEM SELECTOR CHART FOR PENETRATING SYSTEM:
TO SELECT A SNOSTOP PENETRATING SYSTEM FOLLOW THESE STEPS:
- In the left column of TABLE 1 find the row that corresponds to your Ground Snow Load (see Note 1). If you don't know your area's ground snow load, please contact Snostop at 1-877-766-7867. Snostop has gathered ground snow load data from over 3800 stations across Canada (National Research Council) and USA (National Climatic Control Center). However, please note that drifting conditions must be taken into consideration when making your calculations. All Snostop design calculations are based on two lineal feet. If you space the system further apart please note that not only are you increasing the snow load between brackets, but you are diminishing the system's strength as well. For system strengths contact us at at 1-877-766-786.
You may estimate your roof loading also based on your observations and use the Snow Depth column. We will look up values for the nearest weather station, and select the higher value to estimate the load for your snow retention system. Find a column that corresponds to your roof slope and look up the Fence Snow Load. Divide this value by 10 and then multiply it by the Rafter Length (in feet). Round the result to the nearest 100 lb.
Example:
Ground Snow Load 2.1kPa (44 psf), Roof Slope 7.5/12 (7'-6" in 12'), Rafter (slope) Length 33 ft.
Solution:
Since that pressure is not listed, select the row for the next higher pressure. Slope 7.5/12 is not listed either, then choose the column for the higher Snow Load. That is column 7/12. Fence Snow Load = 367 lb/2ft for 10 ft of rafter length. Divide this value by 10 and then multiply it by the rafter length. The result is 367 / 10 x 33 = 1211 lb/2ft. Round this value to 1200. Proceed to step 3 to select your snow retention system. In column 24 of TABLE 2 locate the row that contains the rounded load found in step 2. If it is not listed, then choose the row with the next higher load. Choose a suitable bracket spacing. This will define your Bracket Load, F, and the Type of System to be used.
Bracket spacing is usually defined by the spacing of the roof strucutral members (trusses, beams, z-girts, etc.). Brackets must be fastened into these structural members.
Standard 24" spacing is recommended for medium loads (1000 to 2500 lbs). Spacing may be longer for light loads (under 1000 lb), and shorter for high loads (over 2500 lb).
- Choose from the four standard fence systems shown. Fence load must not exceed the maximum bracket load F(max),and the pull-out strength of the #14 self-tapping screw through the roof substrate must be greater than R.
Height of the roof panel seam or corrugation will determine the orientation of the triangular brackets. Fence should always be placed as close as possible to the roof.
Example:
Fence Snow Load was calculated at 1100 lb/2ft (from Table 1). Roof panel seam height is 2.25". Roof wood trusses are 24" apart.
Solution:
In column 24 (Table 2) choose Bracket loading of 1200 lb. This corresponds to double fence system, type LGB, which will clear the 2.25" standing seam.
The maximum pull-out force on one screw is 0.22 x 1200 = 264 lb. Pull-out strenght of #14 self-tapping screw 1.25" long through wood is 206 lb. Therefore, to maintain mimimum safety factor for wood, longer screws must be used.
Snostop standard lengths for #14 tapping screws are 1.25" and 2.5". Others lenghts can be specially ordered.
TO SELECT A SNOSTOP NON-PENETRATING SYSTEM FOLLOW THESE STEPS:
- In the left column of TABLE 1 find the row that corresponds to your Ground Snow Load (see Note 1). If you don't know your area's ground snow load, please contact Snostop at 1-877-766-7867. Snostop has gathered ground snow load data from over 3800 stations across Canada (National Research Council) and USA (National Climatic Control Center). However, please note that drifting conditions must be taken into consideration when making your calculations. All Snostop design calculations are based on two lineal feet. If you space the system further apart please note that not only are you increasing the snow load between brackets, but you are diminishing the system's strength as well. For system strengths contact us at at 1-877-766-7867.
You may estimate your roof loading also based on your observations and use the Snow Depth column. We will look up values for the nearest weather station, and select the higher value to estimate the load for your snow retention system. Find a column that corresponds to your roof slope and look up the Fence Snow Load. Divide this value by 10 and then multiply it by the Rafter Length (in feet). Round the result to the nearest 100 lb.
Example:
Ground Snow Load 2.1kPa (44 psf), Roof Slope 7.5/12 (7'-6" in 12'), Rafter (slope) Length 33 ft.
Solution:
Since that pressure is not listed, select the row for the next higher pressure. Slope 7.5/12 is not listed either, then choose the column for the higher Snow Load. That is column 7/12. Fence Snow Load = 367 lb/2ft for 10 ft of rafter length. Divide this value by 10 and then multiply it by the rafter length. The result is 367 / 10 x 33 = 1211 lb/2ft. Round this value to 1200. Proceed to step 3 to select your snow retention system. In column 24 of TABLE 2 locate the row that contains the rounded load found in step 2. If it is not listed, then choose the row with the next higher load. Choose a suitable bracket spacing. This will define your Bracket Load, F and the Type of System to be used. Bracket spacing is defined by the spacing of the roof panel standing seams. Brackets must be clamped onto these seams.
- Choose from the two standard fence systems shown. Fence load must not exceed the maximum bracket load F (max).
Example:
Fence Snow Load was calculated at 1100 lb/2ft (from Table 1). Roof panel seams are 24" apart.
Solution:
In column 24 (Table 2) choose Bracket loading of 1200 lb. This corresponds to double fence system LGA-SS One pair of set screw holds only 910lb, therfore two pairs of set screws will have to be used.
If you are having diffculty choosing the correct snow management system contact:
Sales – Architectural
Cam Haszczyn
General Manager
1-800-352-6147 ext. 102
cam@roofersworld.com
|
