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Table 36 Roofing types and slope limits for roofs Slope Type of Roofing
Minimum
Maximum
Built-up roofing Asphalt base (graveled) Asphalt base (without gravel) Coal-tar base (graveled) Cold process
1 in 50 1 in 25 1 in 50 1 in 25
1 in 4 1 in 2 1 in 25 1 in 1.33
Asphalt shingles Normal Application Low slope application
1 in 3 1 in 6
No limit No limit
Roll roofing Smooth and mineral surfaced 480 mm (19 in.) wide selvage asphalt roofing Cold application felt
1 in 4 1 in 6 1 in 50
No limit No limit 1 in 1.33
Wood shingles
1 in 4
No limit
Handsplit shakes
1 in 3
No limit
Asbestos-cement corrugated sheets
1 in 4
No limit
Corrugated metal roofing
1 in 4
No limit
Sheet metal shingles
1 in 4
No limit
Slate shingles
1 in 2
No limit
Clay tile
1 in 2
No limit
Glass fibre reinforced polyester roofing panels
1 in 4
No limit
Table 37 Exposure and thickness of wood shingles and machine-grooved shakes – walls Maximum Exposure, mm (in.) Shake or Shingle Length, mm (in.)
Single Coursing
Double Coursing
Minimum Butt Thickness, mm (in.)
400 (16)
190 (71⁄2)
305 (12)
10 (3⁄8)
450 (18)
216 (81⁄2)
356 (14)
11 (7⁄16)
600 (24)
292 (111⁄2)
406 (16)
13 (1⁄2)