Morrisville Unified Development Ordinance - May 2020

Article 5: Development Standards Section 5.6. FloodplainManagement 5.6.5. Standards for Special FloodHazard Areas with Flood Elevation Data

a. A minimum of two flood openings on different sides of each enclosed area subject to flooding;

b. The total net area of all flood openings must be at least one square inch for each square foot of enclosed area subject to flooding; c. If a building has more than one enclosed area, each enclosed area must have flood openings to allow floodwaters to automatically enter and exit; d. The bottom of all required flood openings shall be no higher than one foot above the adjacent grade; e. Floodopenings may be equippedwith screens, louvers, or other coverings or devices, provided they permit the automatic flow of floodwaters in both directions; and f. Enclosures made of flexible skirtingare not consideredenclosures for regulatorypurposes, and, therefore, do not require flood openings. Masonry or wood underpinning, regardless of structural status, is considered an enclosure and requires flood openings as outlined above. E. Additions/Improvements 1. Where additions and/or improvements to pre-FIRM structures, in combination with any interior modifications to the existing structure, do not constitute a substantial improvement, the addition and/or improvements shall be designed to minimize flood damages and shall not be any more nonconforming than the existing structure. 2. Where additions and/or improvements to pre-FIRM structures, in combination with any interior modifications to the existing structure, constitute a substantial improvement, both the existing structure and the addition and/or improvements shall comply with the standards for new construction. 3. Where additions to post-FIRM structures constitute a substantial improvement and involve no modifications to the existing structure other than a standard door in the common wall, only the addition is required to comply with the standards for new construction. 4. Where additions and/or improvements to post-FIRM structures, in combination with any interior modifications to the existing structure, do not constitute a substantial improvement, only the addition and/or improvements is required to comply with the standards for new construction. 5. Where additions and/or improvements to post-FIRM structures, in combination with any interior modifications to the existing structure, constitutes a substantial improvement, both the existing structure and the addition and/or improvements shall comply with the standards for new construction. 6. Where any combination of repair, reconstruction, rehabilitation, addition, or improvement of a building or structure takes place during a ten-year period and their cumulative cost equals or exceeds 50percent of the market valueof the structure before the improvement or repair is started, the improvement or repair must comply with the standards for new construction. For each building or structure, the ten-year period begins on the date of the first improvement or repair of that building or structure subsequent to the effectivedate of thisOrdinance. If the structure has sustained substantial damage, any repairs are considered substantial improvement regardless of the actual repair work performed. The requirement does not, however, include either: a. Any project for improvement of a building required to correct existing health, sanitary, or safety code violations identified by the Building Official and that are the minimum necessary to assume safe living conditions; or b. Any alteration of a historic structure, provided that the alteration will not preclude the structure’s continued designation as a historic structure.

Morrisville, NC

May 26, 2020

Unified Development Ordinance

Page 5-26