TX-558-GS-9
Roof Gutters and Downspouts
For Statewide Use
Natural Resources Conservation Service
CONSERVATION PRACTICE GENERAL SPECIFICATIONS
ROOF RUNOFF STRUCTURE
INSTALLATION OF ROOF GUTTERS AND DOWNSPOUTS
(No.)
Code 558
for
Click here to enter Name of Owner/Operator & Contract Number
I. SCOPE
The work consists of providing the material and labor for installing a roof runoff structure which includes but not limited to: a gutter(s), a downspout(s), supports, fasteners, an outlet(s), and/or conveyance system to collect, control, and dispose of runoff water from roofs. The installation shall be in accordance with NRCS approved construction plans and these specifications.
II. LOCATION
The system shall be located as shown on the drawings or as marked in the field.
III. PUBLIC AND PRIVATE UTILITIES
A. Utilities are defined to be overhead and underground power or communication lines, and pipelines. The contractor should conduct their own search and discovery for utilities in order to lessen or avoid potential damages. Other buried infrastructure, such as landowner-installed drainage tile, private water lines, or electrical lines, are the responsibility of the landowner to locate. The owner/operator shall complete TX-ENG-80A, Utilities Inventory, during planning and return it to the NRCS representative.
B. The owner/operator shall also ensure that TX-ENG-80B, Cooperator Confirmation of the Utility Locator Service, is completed and returned to the NRCS representative prior to layout or any ground disturbance.
C. Cooperators, sponsoring organizations, and/or contractors shall be liable for damage to utilities and damage resulting from disruption of service caused by installation activities. The Natural Resources Conservation Service (NRCS) makes no representation on the existence or non-existence of any utilities. Absence of utilities on drawings is not assurance that no utilities are present at the site.
IV. MATERIALS
A. Gutters and associated hardware shall be new aluminum, galvanized steel, painted steel, coated galvanized steel, or other approved materials. Materials not included in these specifications require approval by the State Conservation Engineer.
B. Downspouts and associated hardware shall be aluminum, galvanized steel, painted steel, coated galvanized steel, plastic PVC or other approved materials. Any plastic that will be exposed to sunlight shall be protected from UV exposure. Materials not included in these specifications require approval by the State Conservation Engineer.
C. Dissimilar metals shall not be in contact with each other.
D. Accessories for gutters or downspouts shall be of like materials. Hardware and accessories shall be of sufficient strength to secure the gutters and downspouts.
E. Materials shall have the following minimum thickness:
Minimum ThicknessGalvanized Steel,
Painted Steel, and Coated Galvanized Steel / Aluminum Materials / Plastic
Gutters / 28 gauge / 0.027 inches / N/A
Downspouts / 28 gauge / 0.20 inches / ASTM D-1785 Schedule 40
Heavy-duty Hangers / 16 gauge / 0.060 inches1 / N/A
Roof Straps / 19 gauge / 0.060 inches / N/A
Wrap-around Straps / 28 gauge / 0.032 inches / N/A
1 If hangers do not have self-bracing sides and/or reinforcing ribs that run the entire length of the hanger, and continue through the points of greatest stress, the nominal thickness shall be 0.075 inches or greater.
F. First Flush Diverters shall be made of durable materials. Plastic or PVC pipe diverters shall meet the same minimum requirements as downspouts. Other first flush diverter materials shall have approval by the field engineer in writing prior to installation.
G. Fasteners and connectors shall be appropriate for use and contact with the materials for the installation and follow manufacturer recommendations. All fasteners, connectors, and any other metal contacting preservative treated wood shall have been evaluated and approved for use by the manufacturer for use in treated lumber.
H. Gutter hangers shall be appropriate for the type of installation (metal building, wooden fascia board) and shall be made of materials that are compatible with the planned system and follow manufacturer recommendations.
V. WOODEN FASCIA BOARDS
A. If wooden fascia boards are being used to support or attach the gutter, all existing material shall be sound wood, free from decay, of good quality and able to support the proposed gutter system. Any rotten boards or those that will not adequately support the gutter system shall be replaced with appropriate materials as specified. Existing boards shall either be treated lumber or sealed to prevent water damage.
B. When new wood fascia boards are being placed to support gutters or downspouts, the following shall be met:
i. New fascia board shall be straight and graded lumber #2 or better and shall be sound and free of or contain minimal knots. All lumber shall have a minimum grading of Number 2 (No. 2 non-dense grading is not acceptable). Unless otherwise specified, all material shall be furnished in American Standard dressed sizes. All sizes specified are nominal sizes.
ii. Untreated lumber used for fascia, wedges, or rigid supports shall meet the requirements of AWPA Standard U1 to the requirements of Use Category 3A ABOVE GROUND Protected (AWPA UC3A – service conditions of Exterior Above Ground Coated and Rapid Water Runoff) and shall be coated with appropriate sealant, such as exterior latex or enamel paint.
iii. Any treated lumber used for fascia, wedges, or rigid supports shall be in accordance with AWPA Standard U1 to the requirements of Use Category 3B ABOVE GROUND Exposed (AWPA UC3B – service conditions of Exterior Construction Above Ground, Uncoated or Poor Water Runoff) or in accordance with approved report by ICC Safe to meet the requirements for Above Ground Use. Each treated wood item delivered to the job site shall be identified with a label, brand, or stamp that includes: the product name or logo; treatment company name and location; names of the preservative components; treatment end use category; minimum retention; and the applicable AWPA treatment standard or the number of the evaluation report from an evaluation service recognized by the International Code Council at http://www.iccsafe.org. Additionally, the treatment shall be non-corrosive to the gutter and downspout material or a waterproof coating shall be applied between the lumber and the gutter to prevent corrosion.
VI. EXISTING ROOF STRUCTURE
The existing roof structure shall be sound and free from decay, corrosion, or other structural issues. Any damaged roof components including but not limited to rafters, shall be replaced or repaired prior to installation of the roof runoff structure(s).
VII. INSTALLATION
A. Gutters
i. The slope and placement of the gutter shall be as specified in the construction plans.
ii. Hangers and straps shall be securely anchored in a manner which will not prevent the entry of water into the gutter.
B. Supports
i. General Requirements – Rigid supports may be used in lieu of wrap-around straps. They shall be a minimum of 1 inch wide, and shall have a minimum thickness of 1/8 inch for steel and 3/16 inch for aluminum. Materials with equivalent strength and durability are acceptable.
ii. The supports shall be securely attached to the fascia board or building and shall contact the entire gutter bottom width. If supports are screwed into the bottom of the gutter, the screw holes shall be sealed to prevent leakage.
iii. Vertical/Horizontal support -- Supports shall be provided as specified in the construction plans using either, a heavy duty gutter hanger and a roof strap, or a heavy duty gutter hanger screwed to the fascia. They shall have a maximum spacing of 18 inches for aluminum gutters and 24 inches for steel gutters. For gutter sizes greater than 6 inches, maximum hanger spacing shall be reduced to 12 inches for aluminum gutters and 18 inches for steel gutters.
iv. Roof straps shall be securely fastened to each gutter hanger and the roof. Hangers shall have self-bracing sides and/or reinforcing ribs that run the entire length of the hanger, and continue through the points of greatest stress. Alternative gutter hangers shall be approved by the NRCS engineer in writing prior to installation.
v. Lateral Support -- Lateral supports, if required, shall be as specified in the construction plans, with a maximum spacing of 8 feet.
vi. Lateral support may be provided with wedges, wrap-around straps, rigid supports, or any combination thereof which will provide necessary inward and/or outward support.
vii. Snow and Ice Supports (if required based on location) -- Wrap-around straps and rigid supports, if required, shall be as specified in the construction plans, with a maximum spacing of 8 feet. Wrap-around straps shall be a minimum of 1 inch wide stock gutter material and be securely fastened to the fascia board or building, and the roof. They shall be in full contact with the bottom and outside face of the gutter, and extend a minimum of 6 inches onto the roof.
C. Downspouts
i. Downspout outlet connections shall be the manufacturer’s preformed outlets for the given size shown on the design, unless otherwise approved.
ii. Supports for vertical downspouts shall be securely fastened at the top and bottom with intermediate supports placed such that the maximum spacing between supports is 10 feet.
iii. Supports for lateral downspouts and cross pipes shall be placed at a maximum spacing of 5 feet.
iv. Where animals or equipment may come in contact and damage downspouts, the downspout shall be protected or installed to prevent such damage. This may be accomplished with a sleeve of steel pipe, schedule 40 PVC or other adequate materials. Protection shall extend up for a minimum of six feet measured from the ground.
VIII. Outlet Conduits
A. Structure shall be equipped with an outlet and drainage combination and an overflow outlet if water is to be stored. Outlet, drain, and overflow shall be plumbed to allow water to a stable outlet (non-erosive location).
B. Underground conduits shall be installed according to the construction plans and the applicable construction specification.
C. Install appurtenances according to the recommendations of the manufacturer and as noted in the construction plans.
D. Where outlet pipe is suspended, adequate support shall be provided. For PVC pipe, spacing shall be as indicated below:
Pipe Size (Inches) / PVC Outlet Pipe Support Spacing (Ft) /Schedule 40 / Schedule 80 /
2 / 5 / 6
3 / 6 / 7
4 / 6.5 / 7.5
5 / 7 / 8
6 / 7.5 / 9
8 / 8 / 9.5
10 / 8.5 / 10
12 / 9.5 / 10.5
IX. Gutter Guards
Gutter Guards if specified shall be installed in accordance with manufacturer’s recommendations.
X. First Flush System
First flush systems shall be equipped with a water valve set to slowly drain the first flush diverter and shall also have a method to clean out the first flush storage area.
XI. Filters
When required, filters shall be installed in accordance with the manufacturer’s recommendations. In the absence of manufacturer’s recommendations, filters shall be installed as identified in the plans and by the field engineer.
XII. Rainwater Storage Facilities
A. Storage facilities shall be installed in accordance with Conservation Practice Standard Watering Facilities Code 614 and appropriate construction specifications.
B. In addition, rainwater storage facilities shall also have:
i. Inlet - It is recommended that inlet piping is installed to minimize turbulence. To minimize turbulence, consider releasing water:
a) near the bottom of the tank and directed upwards; or
b) through a basket filter.
ii. Pickup for the tank outlet - To minimize intake of debris, it is recommended that the pickup for tank outlet should not take water from the surface or directly off the bottom. It is recommended water should exit through rigid outlet piping a minimum of 4 inches from the bottom of the tank. If the water is being used for drinking, a floating pickup outfitted with a fine-mesh screen or filter is recommended.
iii. Tank Overflows - Overflow outlets should be appropriately sized to match the expected inflow. If the overflow draws water from the bottom of the tank, piping must be vented to prevent siphoning and inadvertently emptying the tank. Overflow shall be released to a stable outlet.
iv. Protection from Wildlife and Rodent Intrusion - Where water is being stored for later use, inlets and outlets shall be protected to prevent intrusion of wildlife, rodents or other critters from entering the storage components.
v. Tank Level Indicators (optional item) - Tanks can be fitted with level indicators. (Site tubes made of glass or clear vinyl tubing are not recommended.)
XIII. Connections between multiple tanks (if using multiple tanks)
Isolation valves shall be installed so that individual tanks can be taken offline without interrupting the flow from other tanks.
XIV. UV Protection for All Above Ground PVC fittings and Piping
Even though the PVC may have a UV inhibitor, all aboveground PVC fittings and piping (whether an inlet, outlet, overflow device, or other piping) should be coated with a 2 layers of paint designed for PVC or other method to block UV light.
XV. Traffic Protection
Protect all exposed fittings, piping and ancillary equipment from animal traffic, foot traffic, and vehicle traffic.
XVI. Stabilization of Disturbed Areas
All disturbed areas shall be fertilized, seeded, and mulched or otherwise stabilized as required on the construction plans.
XVII. CERTIFICATION AND GUARANTEE
A. The installing contractor must certify to the purchaser that the materials and installation comply with the requirements of these specifications.
B. The contractor must furnish the purchaser a written guarantee against defective workmanship and materials to cover a period of not less than one year.
XVIII. MEASUREMENT
A. An onsite check of the completed roof runoff collection system will be performed by a USDA-NRCS representative. Measurement of the system shall be:
i. The installed gutter length(s) shall be measured in feet to the nearest linear foot.
ii. The installed storage tank(s) total storage capacity shall be determined in gallons to the nearest whole gallon.
B. An itemized list of installed materials from suppliers will be provided to confirm gutter and downspout material type, thickness, nominal size, length, and type of hanger.
XIX. CONSTRUCTION DETAILS
A. Gutters and Appurtenances Selected: