Village of Larchmont, NY Construction Standards

All new construction, including manufactured homes and recreational vehicles on site 180 days or longer and not fully licensed for highway use, shall be located landward of the reach of high tide.

The use of fill for structural support of buildings, manufactured homes or recreational vehicles on site 180 days or longer is prohibited.

Man-made alteration of sand dunes which would increase potential flood damage is prohibited.

Subdivision proposals. The following standards apply to all new subdivision proposals and other proposed development in areas of special flood hazard (including proposals for manufactured home and recreational vehicle parks and subdivisions):

Proposals shall be consistent with the need to minimize flood damage.

Public utilities and facilities such as sewer, gas, electrical and water systems shall be located and constructed so as to minimize flood damage.

Adequate drainage shall be provided to reduce exposure to flood damage.

Encroachments.

Within Zones A1-A30 and AE, on streams without a regulatory floodway, no new construction, substantial improvements or other development (including fill) shall be permitted unless:

The applicant demonstrates that the cumulative effect of the proposed development, when combined with all other existing and anticipated development, will not increase the water surface elevation of the base flood more than one foot at any location; or

The Village of Larchmont agrees to apply to the Federal Emergency Management Agency (FEMA) for a conditional FIRM revision, FEMA approval is received and the applicant provides all necessary data, analyses and mapping and reimburses the Village of Larchmont for all fees and other costs in relation to the application. The applicant must also provide all data, analyses and mapping and reimburse the Village of Larchmont for all costs related to the final map revision.

On streams with a regulatory floodway, as shown on the Flood Boundary and Floodway Map or the Flood Insurance Rate Map adopted in § 337-6, no new construction, substantial improvements or other development in the floodway (including fill) shall be permitted unless:

A technical evaluation by a licensed professional engineer shows that such an encroachment shall not result in any increase in flood levels during the occurrence of the base flood; or

The Village of Larchmont agrees to apply to the Federal Emergency Management Agency (FEMA) for a conditional FIRM and floodway revision, FEMA approval is received and the applicant provides all necessary data, analyses and mapping and reimburses the Village of Larchmont for all fees and other costs in relation to the application. The applicant must also provide all data, analyses and mapping and reimburse the Village of Larchmont for all costs related to the final map revisions.

§ 337-16 Standards for all structures.

Anchoring. New structures and substantial improvement to structures in areas of special flood hazard shall be anchored to prevent flotation, collapse or lateral movement during the base flood. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.

Construction materials and methods.

New construction and substantial improvements to structures shall be constructed with materials and utility equipment resistant to flood damage.

New construction and substantial improvements to structures shall be constructed using methods and practices that minimize flood damage.

Enclosed areas.

For enclosed areas below the lowest floor of a structure within Zones A1-A30, AE or AH and also Zone A, if base flood elevation data is available, new and substantially improved structures shall have fully enclosed areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement and which are subject to flooding designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a licensed professional engineer or architect or meet or exceed the following minimum criteria:

[1]

A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.

[2]

The bottom of all such openings shall be no higher than one foot above the lowest adjacent finished grade.

Openings may be equipped with louvers, valves, screens or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters. Enclosed areas subgrade on all sides are considered basements and are not permitted.

Within Zones V1-V30 and VE, and also within Zone V if base flood elevation are available, new construction and substantial improvements shall have the space below the lowest floor either free from obstruction or constructed with nonsupporting breakaway walls, open wood lattice-work or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. The enclosed space below the lowest floor shall be used only for parking vehicles, building access or storage. Use of this space for human habitation is expressly prohibited. The construction of stairs, stairwells and elevator shafts are subject to the design requirements for breakaway walls.

Utilities.

New and replacement electrical equipment, heating, ventilating, air conditioning, plumbing connections, and other service equipment shall be located at or above the base flood elevation. Electrical wiring and outlets, switches, junction boxes and panels shall be elevated to or above the base flood elevation unless they conform to the appropriate provisions of the electrical part of the Building Code of New York State or the Residential Code of New York State for location of such items in wet locations.

New and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system.

New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters. Sanitary sewer and storm drainage systems for buildings that have openings below the base flood elevation shall be provided with automatic backflow valves or other automatic backflow devices that are installed in each discharge line passing through a building's exterior wall.

On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

§ 337-17 Residential structures (except coastal high-hazard areas).

Elevation. The following standards, in addition to the standards in §§ 337-15A, 337-15B, and 337-16, apply to structures located in areas of special flood hazard as indicated:

Within Zones A1-A30, AE and AH, and also Zone A if base flood elevation data are available, new construction and substantial improvements shall have the lowest floor (including basement) elevated to or above two feet above the base flood level.

Within Zone A, when no base flood elevation data are available, new and substantially improved structures shall have the lowest floor (including basement) elevated at least three feet above the highest adjacent grade.

Within Zone AO, new and substantially improved structures shall have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as two feet above the depth number specified in feet on the community's Flood Insurance Rate Map enumerated in § 337-6 (at least two feet if no depth number is specified).

Within Zones AH and AO, adequate drainage paths are required to guide floodwaters around and away from proposed structures on slopes.

§ 337-18 Residential structures (coastal high-hazard areas).

The following standards, in addition to the standards in §§ 337-15A, 337-15B and 337-16, apply to structures located in areas of special flood hazard as indicated:

Elevation. New construction and substantial improvements shall be elevated on pilings, columns or shear walls such that the bottom of the lowest horizontal structural member supporting the lowest elevated floor (excluding columns, piles, diagonal bracing attached to the piles or columns, grade beams, pile caps and other members designed to either withstand storm action or break away without imparting damaging loads to the structure) is elevated to or above two feet above base flood level so as not to impede the flow of water.

Determination of loading forces. Structural design shall consider the effects of wind and water loads acting simultaneously during the base flood on all building components.

The structural design shall be adequate to resist water forces that would occur during the base flood. Horizontal water loads considered shall include inertial and drag forces of waves, current drag forces, and impact forces from waterborne storm debris. Dynamic uplift loads shall also be considered if bulkheads, walls, or other natural or man-made flow obstructions could cause wave run-up beyond the elevation of the base flood.

Buildings shall be designed and constructed to resist the forces due to wind pressure. Wind forces on the superstructure include windward and leeward forces on vertical walls, uplift on the roof, internal forces when openings allow wind to enter the house, and upward force on the underside of the house when it is exposed. In the design, the wind should be assumed to blow potentially from any lateral direction relative to the house.

Wind loading values used shall be those required by the building code.

Foundation standards.

The pilings or column foundation and structure attached thereto shall be adequately anchored to resist flotation, collapse or lateral movement due to the effects of wind and water pressures acting simultaneously on all building components. Foundations must be designed to transfer safely to the underlying soil all loads due to wind, water, dead load, live load and other loads (including uplift due to wind and water).

Spread footings and fill material shall not be used for structural support of a new building or substantial improvement of an existing structure.

Pile foundation design.

The design ratio of pile spacing to pile diameter shall not be less than 8:1 for individual piles (this shall not apply to pile clusters located below the design grade). The maximum center-to-center spacing of wood piles shall not be more than 12 feet on center under load-bearing sills, beams, or girders.

Pilings shall have adequate soil penetration (bearing capacity) to resist the combined wave and wind loads (lateral and uplift) associated with the base flood acting simultaneously with typical structure (live and dead) loads, and shall include consideration of decreased resistance capacity caused by erosion of soil strata surrounding the piles. The minimum penetration for foundation piles is to an elevation of five feet below mean sea level (msl) datum if the BFE is +10 msl or less, or to be at least 10 feet below msl if the BFE is greater than +10 msl.

Pile foundation analysis shall also include consideration of piles in column action from the bottom of the structure to the stable soil elevation of the site. Pilings may be horizontally or diagonally braced to withstand wind and water forces.

The minimum acceptable sizes for timber piles are a tip diameter of eight inches for round timber piles and eight inches by eight inches for square timber piles. All wood piles must be treated in accordance with requirements of EPEE-C3 to minimize decay and damage from fungus.

(5)

Reinforced concrete piles shall be cast of concrete having a twenty-eight-day ultimate compressive strength of not less than 5,000 pounds per square inch, and shall be reinforced with a minimum of four longitudinal steel bars having a combined area of not less than 1% nor more than 4% of the gross concrete area. Reinforcing for precast piles shall have a concrete cover of not less than 1 1/4 inches for No. 5 bars and smaller and not less than 1 1/2 inches for No. 6 through No. 11 bars. Reinforcement for piles cast in the field shall have a concrete cover of not less than two inches.

(6)

Piles shall be driven by means of a pile driver or drop hammer, jetted, or augered into place.

(7)

Additional support for piles in the form of bracing may include lateral or diagonal bracing between piles.

(8)

When necessary, piles shall be braced at the ground line in both directions by a wood timber grade beam or a reinforced concrete grade beam. These at-grade supports should be securely attached to the piles to provide support even if scoured from beneath.

(9)

Diagonal bracing between piles, consisting of two-inch by eight-inch (minimum) members bolted to the piles, shall be limited in location to below the lowest supporting structural member and above the stable soil elevation, and aligned in the vertical plane along pile rows perpendicular to the shoreline. Galvanized steel rods (minimum diameter 1/2 inch) or cable-type bracing is permitted in any plane.

(10)

Knee braces, which stiffen both the upper portion of a pile and the beam-to-pile connection, may be used along pile rows perpendicular and parallel to the shoreline. Knee braces shall be two-by-eight lumber bolted to the sides of the pile/beam, or four-by-four or larger braces framed into the pile/beam. Bolting shall consist of two 5/8-inch galvanized steel bolts (each end) for two-by-eight members, or one 5/8-inch lag bolt (each end) for square members. Knee braces shall not extend more than three feet below the elevation of the base flood.

Column foundation design. Masonry piers or poured-in-place concrete piers shall be internally reinforced to resist vertical and lateral loads, and be connected with a movement-resisting connection to a pile cap or pile shaft.

Connectors and fasteners. Galvanized metal connectors, wood connectors, or bolts of size and number adequate for the calculated loads must be used to connect adjoining components of a structure. Toe nailing as a principal method of connection is not permitted. All metal connectors and fasteners used in exposed locations shall be steel, hot-dipped galvanized after fabrication. Connectors in protected interior locations shall be fabricated from galvanized sheet.

Beam to pile connections. The primary floor beams or girders shall span the supports in the direction parallel to the flow of potential floodwater and wave action and shall be fastened to the columns or pilings by bolting, with or without cover plates. Concrete members shall be connected by reinforcement, if cast in place, or (of precast) shall be securely connected by bolting and welding. If sills, beams, or girders are attached to wood piling at a notch, a minimum of two 5/8-inch galvanized steel bolts or two hot-dipped galvanized straps 3/16 inch by four inches by 18 inches, each bolted with two 1/2-inch lag bolts per beam member, shall be used. Notching of pile tops shall be the minimum sufficient to provide ledge support for beam members without unduly weakening pile connections. Piling shall not be notched so that the cross-section is reduced below 50%.

Floor and deck connections.

Wood two-inch by four-inch (minimum) connectors or metal joist anchors shall be used to tie floor joists to floor beams/girders. These should be installed on alternate floor joists, at a minimum. Cross bridging of all floor joists shall be provided. Such cross-bridging may be one-inch by three-inch members, placed eight feet on-center maximum, or solid bridging of the same depth as joist at same spacing.

Plywood should be used for subflooring and attic flooring to provide good torsional resistance in the horizontal plane of the structure. The plywood should not be less than 3/4-inch total thickness, and should be exterior grade and fastened to beams or joists with 8d annular or spiral thread galvanized nails. Such fastening shall be supplemented by the application of waterproof industrial adhesive applied to all bearing surfaces.

Exterior wall connections. All bottom plates shall have any required breaks under a wall stud or an anchor bolt. Approved anchors will be used to secure rafters or joists and top and bottom plates to studs in exterior and bearing walls to form a continuous tie. Continuous 15/32-inch or thicker plywood sheathing, overlapping the top wall plate and continuing down to the sill, beam, or girder, may be used to provide the continuous tie. If the sheets of plywood are not vertically continuous, then two-by-four nailer blocking shall be provided at all horizontal joints. In lieu of the plywood, galvanized steel rods of 1/2-inch diameter or galvanized steel straps not less than one inch wide by 1/16 inch thick may be used to connect from the top wall plate to the sill, beam, or girder. Washers with a minimum diameter of three inches shall be used at each end of the 1/2-inch round rods. These anchors shall be installed no more than two feet from each corner rod, no more than four feet on center.

Ceiling joist/rafter connections.

All ceiling joists or rafters shall be installed in such a manner that the joists provide a continuous tie across the rafters. Ceiling joists and rafters shall be securely fastened at their intersections. A metal or wood connector shall be used at alternate ceiling joist/rafter connections to the wall top plate.

Gable roofs shall be additionally stabilized by installing two-by-four blocking on two-foot centers between the rafters at each gable end. Blocking shall be installed a minimum of eight feet toward the house interior from each gable end.

Projecting members. All cantilevers and other projecting members must be adequately supported and braced to withstand wind and water uplift forces. Roof eave overhangs shall be limited to a maximum of two feet and joist overhangs to a maximum of one foot. Larger overhangs and porches will be permitted if designed or reviewed by a registered professional engineer or architect and certified in accordance with § 337-13.

Roof sheathing.

Plywood, or other wood material, when used as roof sheathing, shall not be less than 15/32 inch in thickness, and shall be of exterior sheathing grade or equivalent. All attaching devices for sheathing and roof coverings shall be galvanized or be of other suitable corrosion-resistant material.

All corners, gable ends, and roof overhangs exceeding six inches shall be reinforced by the application of waterproof industrial adhesive applied to all bearing surfaces of any plywood sheet used in the sheathing of such corner, gable end, or roof overhang.

In addition, roofs should be sloped as steeply as practicable to reduce uplift pressures, and special care should be used in securing ridges, hips, valleys, eaves, vents, chimneys, and other points of discontinuity in the roofing surface.

Protection of openings. All exterior glass panels, windows, and doors shall be designed, detailed, and constructed to withstand loads due to the design wind speed of 75 miles per hour. Connections for these elements must be designed to transfer safely the design loads to the supporting structure. Panel widths of multiple-panel sliding glass doors shall not exceed three feet.

Breakaway wall design standards.

The breakaway wall shall have a design safe loading resistance of not less than 10 pounds per square foot and not more than 20 pounds per square foot, with the criterion that the safety of the overall structure at the point of wall failure be confirmed using established procedures. Grade beams shall be installed in both directions for all piles considered to carry the breakaway wall load. Knee braces are required for front row piles that support breakaway walls.

Use of breakaway wall strengths in excess of 20 pounds per square foot shall not be permitted unless a registered professional engineer or architect has developed or reviewed the structural design and specifications for the building foundation and breakaway wall components, and certifies that (1) the breakaway walls will fail under water loads less than those that would occur during the base flood; and (2) the elevated portion of the building and supporting foundation system will not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and nonstructural). Water loading values used shall be those associated with the base flood. Wind loading values shall be those required by the building code.

§ 337-19 Nonresidential structures (except coastal high-hazard areas).

The following standards apply to new and substantially improved commercial, industrial and other nonresidential structures, in addition to the requirements in §§ 337-15A, 337-15B and 337-16.

Within Zones A1-A30, AE and AH and also Zone A, if base flood elevation data is available, new construction and substantial improvements of any nonresidential structure, together with attendant utility and sanitary facilities, shall either:

Have the lowest floor, including basement or cellar, elevated to or above two feet above the base flood elevation; or

Be floodproofed so that the structure is watertight below two feet above the base flood level with walls substantially impermeable to the passage of water. All structural components located below the base flood level must be capable of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy.

Within Zone AO, new construction and substantial improvements of nonresidential structures shall:

Have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as two feet above the depth number specified in feet on the community's FIRM (at least two feet if no depth number is specified); or

Together with attendant utility and sanitary facilities, be completely floodproofed to that level to meet the floodproofing standard specified in § 337-16C.

If the structure is to be floodproofed, a licensed professional engineer or architect shall develop and/or review structural design, specifications and plans for construction. A floodproofing certificate or other certification shall be provided to the local administrator that certifies that the design and methods of construction are in accordance with accepted standards of practice for meeting the provisions of § 337-19A(2), including the specific elevation (in relation to mean sea level) to which the structure is to be floodproofed.

Within Zones AH and AO, adequate drainage paths are required to guide floodwaters around and away from proposed structures on slopes.

Within Zone A, when no base flood elevation data is available, the lowest floor (including basement) shall be elevated at least three feet above the highest adjacent grade.

§ 337-20 Nonresidential structures (coastal high-hazard areas).

In Zones V1-V30 and VE, and also Zone V if base flood elevations are available, new construction and substantial improvements of any nonresidential structure, together with attendant utility and sanitary facilities, shall have the bottom of the lowest member of the lowest floor elevated to or above the base flood elevation. Floodproofing of structures is not an allowable alternative to elevating the lowest floor to the base flood elevation in Zones V1-V30, VE and V.

§ 337-21 Manufactured homes and recreational vehicles.

The following standards, in addition to the standards in §§ 337-15 and 337-16 apply, as indicated, in areas of special flood hazard to manufactured homes and to recreational vehicles which are located in areas of special flood hazard.

Recreational vehicles.

Recreational vehicles placed on sites within Zones A1-A30, AE and AH shall either:

Be on site fewer than 180 consecutive days;

Be fully licensed and ready for highway use; or

(c)

Meet the requirements for manufactured homes in Subsections B, D and E.