64-321 - Measurement of height for flood-resistant buildings

LAST AMENDED
5/12/2021


In all districts, as an alternative to measuring heights from #base plane#, #curb level#, or other applicable datum, all height measurements in #flood
zones#, including the number of #stories# permitted, as applicable, may be measured from the #reference plane#, except as follows:

(a)    for #Quality Housing Buildings#, any minimum base height requirements shall continue to be measured from the #base plane#; and

(b)    the provisions of this Section shall not apply:

        (1)    to fences or other structures that are not #buildings#; and

        (2)    to #buildings# that are #accessory# to #single-# or #two-family residences#, except when mechanical equipment is located within such
                #building#.

Illustrative Examples

The following examples, although not part of the Zoning Resolution, are included to demonstrate the application of the optional height regulations
available to #zoning lots# in #flood zones#. Specially, the examples illustrate how the defined terms #reference plane#, from which height is measured,
relates to the #flood-resistant construction elevation# and the #first story above the flood elevation#. All terms are defined in Section 64-11
(Definitions).

EXAMPLE 1
A #zoning lot# located within the #high-risk flood zone# has a #flood-resistant construction elevation# (as defined in Section 64-11) that equates to
being located six feet above grade (for illustrative purposes). The owner of a #single-family# #detached# #residence# would like to elevate the first
habitable floor three feet above the #flood-resistant construction elevation# and wet-floodproof the ground floor up to that same level (nine feet above
grade) to account for sea level rise projections.

Pursuant to Section 64-321, height measurements in #flood zones#, including height and setback regulations, may start from the #reference plane#,
allowing the owner the necessary flexibility to address long-term climate change. For #zoning lots# located within the #high-risk flood zone#, the
#reference plane#, may be established at any level between the #flood-resistant construction elevation# and a height of 10 feet above the #base plane# or
#curb level#, as applicable. (Where the #flood-resistant construction elevation# exceeds 10 feet, the #reference plane# may still be established at the
#flood-resistant construction elevation#, but that is not the case here.) While there is a level of flexibility built into the #reference plane# definition, the
#reference plane# itself must also be located at or below the #first story above flood elevation#.

Considering the owner of such #single-family# #detached# #residence# is proposing to wet-floodproof the ground floor up to nine feet above grade,
the #first story above flood elevation# becomes the finished floor level of the first #story# located at or above nine feet, which is, in this case, the second
#story#. Therefore, the #reference plane# was able to be situated at that same level (nine feet above grade), but not higher.

EXAMPLE 2
A #zoning lot# located within the #moderate-risk flood zone# has a #flood-resistant construction elevation# (as defined in Section 64-11) of two feet
above the lowest grade adjacent to the #building or other structure#. The owner of a #mixed building# that was flooded during Hurricane Sandy,
would like to proactively comply with #flood-resistant construction standards# to be better prepared in the event of a future storm. To realize that, the
owner decided to elevate the ground floor with a #commercial# #use# to the #flood-resistant construction elevation#, and dry-floodproof one foot
above that for extra safety.

Pursuant to Section 64-321, height measurements in #flood zones#, including height and setback regulations, may start from the #reference plane#,
allowing the owner the necessary flexibility to address long-term climate change. For #zoning lots# located within the #moderate-risk flood zone#, the
#reference plane# may be established at any level between the #flood-resistant construction elevation# and a height of five feet above the #base plane# or
#curb level#, as applicable. While there is a level of flexibility built within the #reference plane# definition, the #reference plane# must also be located at
or below the #first story above flood elevation#.

Considering that the owner of such #mixed building# is proposing to elevate and dry-floodproof the ground floor up to three feet above grade, the
#first story above flood elevation# becomes the finished floor level of the first #story# located at or above three feet, which is, in this case, the second
#story#. Therefore, the #reference plane# was able to be situated at five feet above the #base plane# or #curb level#, as applicable.