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Coastal Building Materials
Home Builder’s Guide to Coastal Construction
FEMA 499/June 2005
Technical Fact Sheet No. 8

Purpose: To provide guidance on the selection of building materials used for
coastal construction.

Key Issues
--The durability of a coastal home relies on the types of materials used to
construct it. For more details, see the U.S. Department of Housing and Urban
Development (HUD) report Durability by Design, A Guide for Residential Builders
and Designers, available on the HUD User website at
http://www.huduser.org/publications/destech/durdesign.html.
--Materials and construction methods should be resistant to flood and wind
damage, driving rain, corrosion, moisture, and decay.
--All coastal buildings will require maintenance and repairs (more so than
inland construction) — use proper materials and methods for repairs, additions,
and other work following initial construction (see Fact Sheet No. 30).

Section 60.3(a)(ii) of the National Flood Insurance Program (NFIP) regulations
requires
that all new construction and substantial improvements in floodprone areas be
constructed with materials below the Base Flood Elevation (BFE) that are
resistant to
flood damage. (See Fact Sheet No. 30 for a definition of “substantial
improvement.”)

Flood-Resistant Materials
Flooding accounts for a large percentage of the damage caused by a coastal
storm. Building materials exposed to flooding must be resilient enough to
sustain a certain amount of water exposure in order to avoid the need for
complete replacement after the flood.

FEMA defines a flood-resistant material as any building material capable of
withstanding direct and prolonged contact (i.e., at least 72 hours) with
floodwaters without sustaining significant damage (i.e., requires more than
cosmetic repair).

The following are examples of flood-resistant materials:
--Lumber: pressure-treated or naturally decay-resistant, including redwood,
cedar, some oaks, and bald cypress
--Concrete: a sound, durable mix, and when exposed to saltwater or salt spray,
made with a sulfate-resisting cement, with a 28-day compressive strength of
5,000 psi minimum and a water-cement ratio not higher than 0.40 – consult ACI
318-02, Building Code Requirements for Structural Concrete and Commentary, by
the American Concrete Institute International
--Masonry: reinforced and fully grouted
--Structural Steel: coated to resist corrosion
--Insulation: plastics, synthetics, and closed-cell foam, or other types
approved by local building officials

This table lists examples of flood-resistant materials used in coastal homes.
Table description: two columns: Location of Material Use and Name of Material

--Piles and Posts: Round, tapered wood piles preservative-treated for ground
contact, at a minimum; square-section piles or wood posts preservative-treated
for marine use.
--Piers: reinforced concrete or concrete masonry units (CMU) (see “Flood-
Resistant Materials” above and Fact Sheet No. 14)
--Foundation walls: reinforced concrete or CMU, or wood that is preservative-
treated for foundation or marine use (see Fact sheet No. 15)
--Beams: solid sawn timbers and glue-laminated products, either naturally decay-
resistant or preservative-treated for aboveground exposure; built-up members
preservative-treated for ground contact
--Decking: preservative-treated or naturally decay-resistant wood, or composite
wood members (e.g., manufactured of recycled sawdust and plastic)
--Framing: sawn wood or manufactured lumber (preservative-treated or naturally
resistant to decay if in close proximity to the ground)
--Exterior sheathing: high-capacity shearwall sheathing rated “exterior”
--Subflooring: plywood or oriented strand board (OSB) rated “Exposure 1,” or
rated “exterior” if left permanently exposed (e.g., exposed underside of
elevated house on open foundation)
--Siding: vinyl or naturally decay-resistant wood (see Fact Sheet No. 25)
--Flooring: latex or bituminous cement formed-in-place, clay, concrete tile,
pre-cast concrete, epoxy formed-in-place, mastic flooring, polyurethane formed–
in-place, rubber sheets, rubber tiles with chemical-set adhesives, silicone
floor formed –in-place, terrazzo, vinyl sheet-goods, vinyl tile with chemical-
set adhesives, pressure-treated lumber or naturally decay-resistant lumber.
--Walls and Ceilings: cement board, brick, metal, cast stone in waterproof
mortar, slate, porcelain, glass, glass block, clay tile, concrete, CMU,
pressure-treated wood, naturally decay-resistant wood, marine grad plywood or
pressure-treated plywood.
--Doors: hollow metal
--Insulation: foam or closed-cell
--Trim: natural or artificial stone, steel, or rubber

Many coastal jurisdictions make available a list of approved materials that can
be used in coastal environments. Check for locally approved flood-resistant
materials. Include all proposed construction and materials in approved plans.
For guidance on testing specific materials, refer to NES Evaluation Protocol for
Determination of Flood-Resistant Properties of Building Elements (NES, Inc. –
http://www.nateval.org).

Wind-Resistant Materials
Homes in many coastal areas are often exposed to winds in excess of 90 mph (3-
second peak gust). Choose building materials (e.g., roof shingles, siding,
windows, doors, fasteners, and framing members) that are designed for use in
high-wind areas.

Examples:
--shingles rated for high winds (see Fact Sheet No. 20)
--double-hemmed vinyl siding (see Fact Sheet No. 25)
--deformed-shank nails for sheathing attachments (see Fact Sheet No. 18)
--wind-resistant glazing (see Fact Sheet No. 22)
--reinforced garage doors
--tie-down connectors used throughout structure (from roof framing to
foundation — see Fact Sheet Nos. 10 and 17)
--wider framing members (2x6 instead of 2x4)

Remember: a wind-resistant material is only as good as its connection. Always
use recommended fasteners and connection methods.

Corrosion and Decay Resistance
Coastal environments are conducive to metal corrosion and moisture- and termite-
related decay of other building materials. Metal corrosion is most pronounced on
coastal homes (within 3,000 feet of the ocean), but moisture- and termite-
related decay are prevalent throughout coastal areas.

Corrosion-Resistant Metals
Most jurisdictions require metal building hardware to be hot-dipped galvanized
or stainless steel. Some local codes require protective coatings that are
thicker than “off-the-shelf” products typically have. For example, a G90 zinc
coating (0.75 mil on each face) may be required, which is thicker than the
common G60 (0.5 mil on each face) coating.

Recommendations
--Use hot-dipped galvanized or stainless steel hardware. Reinforcing steel
should be protected from corrosion by sound materials (masonry, mortar, grout,
concrete) and good workmanship (see Fact Sheet No. 16). Use galvanized or epoxy-
coated reinforcing steel in situations where the potential for corrosion is high
(see Fact Sheet No. 14).
--Avoid joining dissimilar metals, especially those with high galvanic
potential (e.g., copper and steel).
--Some wood preservatives should not be used in direct contact with
galvanized metal. Verify that wood treatment is suitable for use with galvanized
metal, or use stainless steel.
--Metal-plate-connected trusses should not be exposed to the elements. Truss
joints near vent openings are more susceptible to corrosion and may require
increased corrosion protection.

The term "corrosion-resistant" is widely used but, by itself, is of little help
to those specifying or evaluating materials for use in a coastal home. Every
material resists corrosion to some extent, or conversely, every material
corrodes.

The real issue is how long will a given material serve its intended purpose at a
given home? The answer depends on the following:
--the material
--where it is used in the home
--whether installation techniques (e.g., drilling, cutting, bending) will
compromise its resistance
--its degree of exposure to salt air, moisture, and corrosive agents
--whether maintenance required of the homeowner is performed

The bottom line: do not blindly specify or accept a product just because it is
labeled corrosion-resistant. Evaluate the nature of the material, its coating
type and thickness (if applicable), and its performance in similar environments
before determining whether it is suitable for a particular application.

For guidance on the selection of metal hardware for use in coastal environments,
consult an engineer with experience in corrosion protection. For more
information about corrosion in coastal environments, see FEMA Technical Bulletin
8-96, Corrosion Protection for Metal Connectors in Coastal Areas for Structures
Located in Special Flood Hazard Areas (see the Additional Resources section of
this fact sheet).

Moisture Resistance
Materials resistant to moisture can greatly reduce maintenance and extend the
life of a coastal home (however, by themselves, such materials cannot prevent
all moisture damage. Proper design and installation of moisture barriers (see
Fact Sheet No. 9) is also required).

Recommendations
--Control wood decay by separating wood from moisture, using preservative-
treated wood, using naturally decay-resistant wood, and applying protective wood
finishes.
--Use proper detailing of wood joints and construction to eliminate standing
water and reduce moisture absorption by the wood (e.g., avoid exposure of end
grain cuts, which absorb moisture up to 30 times faster than the sides of a wood
member).
--Do not use untreated wood in ground contact or high-moisture situations.
Do not use untreated wood in direct contact with concrete.
--Field-treat any cuts or drill holes that offer paths for moisture to enter
wood members.
--For structural uses, employ concrete that is sound, dense, and durable;
control cracks with welded wire fabric and/or reinforcing, as appropriate.
--Use masonry, mortar, and grout that conform with the latest building
codes.

Termite Resistance
Termite damage to wood construction occurs in many coastal areas (attack is most
frequent and severe along the southeastern Atlantic and Gulf of Mexico
shorelines, in California, and in Hawaii and other tropical areas). Termites can
be controlled by soil treatment, termite shields, and the use of termite-
resistant materials.

Recommendations
--Incorporate termite control methods into design in conformance with
requirements of the authority having jurisdiction.
--Where a masonry foundation is used and anchorage to the foundation is
required for uplift resistance, the upper block cores must usually be completely
filled with grout, which may eliminate the requirement for termite shields (see
Fact Sheet No. 14).
--Use preservative-treated wood for foundations, sills, above-foundation
elements, and floor framing.

Additional Resources
FEMA. NFIP Technical Bulletin 2-93, Flood-Resistant Materials Requirements for
Buildings Located in Special Flood Hazard Areas.
(
http://www.fema.gov/fima/techbul.shtm)
FEMA. NFIP Technical Bulletin 8-96, Corrosion Protection for Metal Connectors in
Coastal Areas for Structures Located in Special Flood Hazard Areas.
(
http://www.fema.gov/fima/techbul.shtm)
American Concrete Institute International. (
http://www.aci-
int.org/general/home.asp)
American Wood-Preservers’ Association. (
http://www.awpa.com)
International Code Council Evaluation Service, Inc. Protocol for Testing the
Flood Resistance of Materials. (
http://www.icc-es.org/index.shtml)