Water-Use Facility Dimensions and Roof Overhangs
To provide guidance regarding the inclusion of roof overhangs in the dimensions of water-use facilities and the calculation of the facility footprint.
This guidance applies to private water-use facilities subject to the size restrictions of Sections 1304.204 and 1304.212. These generally include private, residential water-use facilities (individual and community facilities and private waterfront clubs) located on public land managed by TVA (fee land), subject to TVA flowage easement, or on private shoreland subject to the jurisdiction of Section 26a of the TVA Act. Requests for facilities at commercial marinas are not limited to a maximum allowable footprint; but rather, are generally issued harbor limits based on Section 1304.404, and are not subject to this guidance.
The size of water-use facilities on TVA-owned residential access shoreland are governed by subpart C of the Section 26a regulations, specifically: Sections 1304.204, 1304.206, and 1304.212. In general, water-use facilities are limited to a total footprint of 1,000- or 1,800-square feet in accordance with Section 1304.204.
Section 26a regulations do not specifically require roof overhangs to be included or excluded in the calculation of a water-use facility footprint; 1304.204 (b) and (g) pertain to this issue. As described in Section 1304.204(b), the 1,000- or 1,800-square foot area begins at the end of the access walkway; implying the box would begin at the base of the dock (post to post measurement) and would not include the depth of the roof overhang. Consistent with this interpretation, standard practice has been not to include standard roof overhangs in the calculation of the facility footprint, and standard drawings posted on TVA's external website do not include the roof overhangs in the facility dimensions. Situations occur, however, where a non-standard overhang or a cantilevered cover has been incorporated into the design of a facility in a way that merits the inclusion of the overhang's dimensions in the determination of the facility footprint. This guidance provides a framework for determining when to include the overhang in the overall dimensions of the facility.
Roof overhangs serve two main functions: to protect the structure from exposure to solar radiation and precipitation, and to minimize the damage associated with such exposure. Standard recommended overhang depths are region specific and are a function of the climate. According to the U.S. Department of Housing and Urban Development (HUD) Office of Policy Development and Research, and the Partnership for Advanced Technology in Housing (PATH), overhang widths should be 12 to 24 inches in moist, humid climates and more if practicable (HUD, 2002). Guidance published by PATH (2006) recommends minimum roof overhangs in the Tennessee Valley region up to 24 inches.
TVA will apply these recommendations for the Valley and consider a standard roof overhang as one that extends no more than 24 inches. This measurement does not include gutters.
When determining the facility dimensions and footprint, staff shall use the guidance outlined below:
- Standard roof overhangs (less than or equal to 24 inches) will not be included in the dimensional analysis of a facility for the purpose of calculating the facility footprint.
- Project Leads can exclude roof overhangs from the dimensions of a water-use facility that are up to 24 inches in horizontal depth (the lookout dimension in Figure 1). Gutters up to six inches are allowed in addition to the 24-inch overhang.
- When an overhang or cantilevered cover exceeds 24 inches, it will be included in the dimensions of the facility and the calculation of the facility footprint. In these cases, the Project Lead will inform the applicant that the overhang will be included in the facility footprint calculation and present them the opportunity to modify their proposed plans. Approved project plans and drawings will contain the roof overhang dimension.
Requests to modify existing, approved facilities will be evaluated on a case-by-case basis to determine if the modification requires compliance with this guidance consistent with Sections 1304.210 and 1304.211.
Figure I. Roof Overhang Dimension