// CODE SNIPPET
1101.8 Areaway Drains
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Open subsurface space adjacent
to a building, serving as an entrance to the basement or
cellar of a building, shall be provided with a drain or drains.
Such areaway drains shall be not less than 2 inches (50
mm) in diameter for areaways at a maximum of 100 square
feet (9.29 m2) in area, and shall be discharged in the manner
provided for subsoil drains not serving continuously
flowing springs or groundwater (see Section 1101.6.1). Areaways in excess of 100 square feet (9.29 m2) shall not
drain into subsoil drains. Areaway drains for areaways
exceeding 100 square feet (9.29 m2) shall be sized in accordance
with Table 1101.8.
For SI units: 1 inch = 25 mm, 1 gallon per minute = 0.06 L/s, 1/8 inch per foot = 10.4 mm/m, 1 inch per hour = 25.4 mm/h, 1 square foot = 0.0929 m2
Notes:
1 The sizing data for horizontal piping are based on the pipes flowing full.
SIZE OF PIPE | FLOW (1/8 inch per foot slope) |
MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet) |
|||||
inches | gpm | 1 (in/h) | 2 (in/h) | 3 (in/h) | 4 (in/h) | 5 (in/h) | 6 (in/h) |
3 | 34 | 3288 | 1644 | 1096 | 822 | 657 | 548 |
4 | 78 | 7520 | 3760 | 2506 | 1880 | 1504 | 1253 |
5 | 139 | 13360 | 6680 | 4453 | 3340 | 2672 | 2227 |
6 | 222 | 21400 | 10700 | 7133 | 5350 | 4280 | 3566 |
8 | 478 | 46000 | 23000 | 15330 | 11500 | 9200 | 7670 |
10 | 860 | 82800 | 41400 | 27600 | 20700 | 16580 | 13800 |
12 | 1384 | 133200 | 66600 | 44400 | 33300 | 26650 | 22200 |
15 | 2473 | 238000 | 119000 | 79333 | 59500 | 47600 | 39650 |
SIZE OF PIPE | FLOW ( 1/4 inch per foot slope) |
MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet) |
|||||
inches | gpm | 1 (in/h) | 2 (in/h) | 3 (in/h) | 4 (in/h) | 5 (in/h) | 6 (in/h) |
3 | 48 | 4640 | 2320 | 1546 | 1160 | 928 | 773 |
4 | 110 | 10600 | 5300 | 3533 | 2650 | 2120 | 1766 |
5 | 196 | 18880 | 9440 | 6293 | 4720 | 3776 | 3146 |
6 | 314 | 30200 | 15100 | 10066 | 7550 | 6040 | 5033 |
8 | 677 | 65200 | 32600 | 21733 | 16300 | 13040 | 10866 |
10 | 1214 | 116800 | 58400 | 38950 | 29200 | 23350 | 19450 |
12 | 1953 | 188000 | 94000 | 62600 | 47000 | 37600 | 31350 |
15 | 3491 | 336000 | 168000 | 112000 | 84000 | 67250 | 56000 |
SIZE OF PIPE | FLOW ( 1/2 inch per foot slope) |
MAXIMUM ALLOWABLE HORIZONTAL PROJECTED ROOF AREAS AT VARIOUS RAINFALL RATES (square feet) |
|||||
inches | gpm | 1 (in/h) | 2 (in/h) | 3 (in/h) | 4 (in/h) | 5 (in/h) | 6 (in/h) |
3 | 68 | 6576 | 3288 | 2192 | 1644 | 1310 | 1096 |
4 | 156 | 15040 | 7520 | 5010 | 3760 | 3010 | 2500 |
5 | 278 | 26720 | 13360 | 8900 | 6680 | 5320 | 4450 |
6 | 445 | 42800 | 21400 | 14267 | 10700 | 8580 | 7140 |
8 | 956 | 92000 | 46000 | 30650 | 23000 | 18400 | 15320 |
10 | 1721 | 165600 | 82800 | 55200 | 41400 | 33150 | 27600 |
12 | 2768 | 266400 | 133200 | 88800 | 66600 | 53200 | 44400 |
15 | 4946 | 476000 | 238000 | 158700 | 119000 | 95200 | 79300 |
Notes:
1 The sizing data for horizontal piping are based on the pipes flowing full.
2 For rainfall rates other than those listed, determine the allowable roof area by dividing the area given in the 1 inch per hour (25.4 mm/h) column by the
desired rainfall rate.
Related Code Sections
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