Accessory Structures

The purpose of this page is to define Accessory Structures, a commonly used term in floodplain management.

Definition/Description

Accessory structures are also referred to as appurtenant structures. An accessory structure is a structure which is on the same parcel of property as a principal structure and the use of which is incidental to the use of the principal structure. For example a residential structure may have a detached garage or storage shed for garden tools as accessory structures. Other examples of accessory structures include gazebos, picnic pavilions, boathouses, small pole barns, storage sheds, and similar buildings. National Flood Insurance Program (NFIP) regulations for new construction generally apply to new and substantially improved accessory structures.

NFIP Requirement

•    59.1 - Definition
•    60.3 - Flood plain management criteria for flood-prone areas
  •    (a) (3) - Reasonably Safe From Flooding
  •    (c) (3) - A Zone Nonresidential Buildings
  •    (c) (5) - Openings

Other Applicable NFIP Regulations

•     60.3 - Flood plain management criteria for flood-prone areas
  •     (c) (8) - Zone AO Nonresidential Buildings
  •     (c) (10) - Cumulative Effects of Development
  •     (d) (3) - Floodway Encroachment
  •     (e) (4) - V Zone Structures

Guidance

• IS-9 Managing Floodplain Development Through The National Flood Insurance Program (NFIP) (pages 5-41, 5-42)
• Technical Bulletin 7, Wet Floodproofing Requirements for Structures Located in Special Flood Hazard Areas (FIA-TB-7)

Related Keywords

• Anchoring
• Appurtenant Structure
• Development
• Elevation
• Garages
• Lowest Floor
• Permit for Floodplain Development
• Substantial Improvement
• Variance

Special Topic Resources

• Flood Resistant Materials
• Floodproofing
• V Zone Construction

Supplemental Information for Accessory Structures

Under limited circumstances communities may issue variances to permit construction of wet-floodproofed accessory structures. These accessory structures must be low value and not be used for human habitation. They must also meet the following requirements:

1. Accessory structures shall be designed to have low flood damage potential.
2. Accessory structures shall be constructed and placed on the building site so as to offer the minimum resistance to the flow of floodwaters.
3. Accessory structures shall be firmly anchored to prevent flotation which may result in damage to other structures.
4. Service facilities such as electrical and heating equipment shall be elevated or floodproofed.
5. Accessory structures shall have openings as required under 60.3(c)(5).
6. Floodway encroachment provision of 60.3 (d) (3) must be met.