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Gutters and Downspouts:
Downspouts
Description: Copper downspouts are usually shop fabricated using 16 or 20 oz. cold rolled copper. Plain and corrugated, round and rectangular downspouts are typical. Other decorative downspout designs can also be fabricated.
Special Conditions: Downspouts should be installed vertically wherever possible. All horizontal offsets should be sloped in the direction of flow.
An alternate support method uses brass straps, fastened to 32 oz. copper braces, spaced a maximum of 30" O.C. A brass stiffening bar is required in the gutter bead. This method does not require the use of brackets.
Regardless of the support method, gutters must be hung to intercept the flow of water off the roof. This usually means that the surface to which the gutter is attached is vertical.
Special Conditions: The details shown are based on gutters with rectangular shapes. Half round gutters are also available but are usually supported by straps with spring clips or by special brackets.
A. Typical Downspout Sections This drawing shows typical downspout cross-sections. Downspouts can be fabricated in any size. Table 4.4.10.1 shows the dimensions of standard sizes.
| Type | Area (Sq. In.) | Nominal Size (Inches) | Actual Size (Inches) |
|---|---|---|---|
| Plain | 7.07 | 3 Dia. | 3 Dia. |
| Round | 12.57 | 4 Dia. | 4 Dia. |
| 19.63 | 5 Dia. | 5 Dia. | |
| 28.27 | 6 Dia. | 6 Dia. | |
| Corrugated | 5.91 | 3 Dia. | 3 Dia. |
| Round | 11.01 | 4 Dia. | 4 Dia. |
| 17.72 | 5 Dia. | 5 Dia. | |
| 25.97 | 6 Dia. | 6 Dia. | |
| Corrugated | 3.8 | 2 | 1 3/4 x 2 1/4 |
| Rectangular | 7.73 | 3 | 2 3/8 x 3 1/4 |
| 11.70 | 4 | 2 3/4 x 4 1/4 | |
| 18.75 | 5 | 3 3/4 x 5 | |
| Plain | 3.94 | 2 | 1 3/4 x 2 1/4 |
| Rectangular | 6.00 | 3 | 2 x 3 |
| 12.00 | 4 | 3 x 4 | |
| 20.00 | 5 | 3 3/4 x 4 3/4 | |
| 24.00 | 6 | 4 x 6 |
B. Downspout Assembly This detail illustrates the various components of an installed downspout assembly.
The downspout is joined to the gutter with an outlet tube, see Detail C. The flanges of the outlet tube are soldered to the gutter. Downspout sections are joined together by soldering. The bottom end of the upper section is inserted into the top of the section below it. Copper straps are used to hold the downspout against the building or structure.
Note: Copper drainage tubes can be substituted for the downspouts in all indicated details.
C. Outlet Tube in Gutter Lining The length of the outlet tube is a minimum of 4" from the flange edge to the bottom edge. The flange is 3/8" wide. The outside dimension of the outlet tube is 1/8" less than the inside dimension of the downspout.
The outlet tube is inserted through a hole at the gutter bottom. The hole size equals the outside dimension of the tube. The flange of the tube is soldered to the gutter.
For Additional Information:
- Gutters and Downspouts - Hung Gutters, for information on downspout hangers.
- Gutters and Downspouts - Downspout Hangers, for additional information on hung copper gutters.
Design Handbook
Available in 2 formats:
Download AutoCAD Files
AutoCAD Detail Files
[ZIP - 4.5MB] is a complete set of CAD files for the designs shown in Architectural Details.
The AutoCAD files for individual details can be downloaded from individual topic pages by clicking the CAD File button next to an individual detail.
Order Design Handbook
(publication #A4050).
