Subpart
1.
IBC section 1502.1.
IBC section 1502.1 is amended and subsections are added to read
as follows:
1502.1
Roof
drainage. Design and installation of roof drainage systems shall comply
with Minnesota Rules, chapter 4714, Minnesota Plumbing Code, and the following
provisions:
1502.1.1
Where required.
All roofs shall drain into a separate storm sewer system or to an
approved place of disposal.
1502.1.2
Roof design. Roofs
shall be structurally designed for the maximum possible depth of water that
will pond thereon as determined by the relative levels of roof deck and
overflow weirs, scuppers, edges, or serviceable drains in combination with the
deflected structural elements. In determining the maximum possible depth of
water, all primary roof drainage means shall be assumed to be blocked.
Subp. 1a.
IBC section 1502.2.
IBC section 1502.2 is amended and subsections and Table
1502.2.3 are added to read as follows:
1502.2
Secondary drainage required.
Secondary (emergency) roof drains or scuppers shall be provided where
the roof perimeter construction extends above the roof in such a manner that
water will be entrapped if the primary drains allow buildup for any reason.
1502.2.1
Separate systems required.
Secondary (emergency) 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.
1502.2.2
Sizing of secondary drains. Secondary (emergency) roof drain
systems shall be sized to the same capacity as the primary roof drain areas in
accordance with Minnesota Rules, chapter 4714, the Minnesota Plumbing
Code.
1502.2.3
Sizing of
scuppers. Scuppers shall be sized to prevent the depth of ponding water
from exceeding that for which the roof was designed as determined by this code.
Scuppers shall not have an opening weir length dimension of less than 4 inches
(102 mm) and shall be sized in accordance with Table 1502.2.3. The flow through
the primary system shall not be considered when sizing the secondary roof
drainage system.
TABLE 1502.2.3 SCUPPER SIZING a
| Square feet of Roof Area |
| Head Height in
Inchesb
|
Length of Weir in inches |
| 4 |
6 |
8 |
12 |
16 |
20 |
24 |
| 1 |
273 |
418 |
562 |
851 |
1139 |
1427 |
1715 |
| 2 |
734 |
1141 |
1549 |
2365 |
3180 |
3996 |
4813 |
| 3 |
1274 |
2023 |
2772 |
4270 |
5768 |
7267 |
8766 |
| 4 |
1845 |
2999 |
4152 |
6460 |
8766 |
11073 |
13381 |
| 6 |
2966 |
5087 |
7204 |
11442 |
15860 |
19918 |
24160 |
a Table based upon 4-inch per hour
rainfall.
b Minimum 1-inch vertical free space
above Head (H) is required.
Subp. 2.
IBC section 1502.3.
IBC section 1502.3 is deleted in its entirety.
1305.1510
SECTION 1510, ROOFTOP
STRUCTURES.
IBC section 1510.2.2 is amended to read as follows:
1510.2.2
Use limitations.
Penthouses shall not be used for purposes other than shelter of
mechanical or electrical equipment, tanks, or vertical shaft openings in the
roof assembly.
Exception: Accessory uses necessary for the
maintenance of building systems shall be permitted when the penthouse is
sprinkled in accordance with Section 903.1.1.
