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Selecting a Lot and Siting the Building
Home Builder’s Guide to Coastal Construction
FEMA 499/June 2005
Technical Fact Sheet No. 7

Purpose: To provide guidance on lot selection and siting considerations for
coastal residential buildings.

Key Issues
--Purchase and siting decisions should be long-term decisions, not based on
present-day shoreline and conditions.
--Parcel characteristics, infrastructure, regulations, environmental factors,
and owner desires constrain siting options.
--Conformance with local/state shoreline setback lines does not mean buildings
will be “safe.”
--Information about site conditions and history is available from several
sources.

Siting, design, and construction should be considered together (see Fact Sheet
No. 6), but know that poor lot selection and siting decisions can rarely be
overcome by improved design and construction. Building failures (see Fact Sheet
No. 1) are often the result of poor siting.

The Importance of Property Purchase and Siting Decisions
The single most common and costly siting mistake made by designers, builders,
and owners is failing to consider future erosion and slope stability when an
existing coastal home is purchased or when land is purchased and a new home is
built. Purchase decisions — or siting, design, and construction decisions —
based on present-day shoreline conditions often lead to future building
failures.

Over a long period of time, owners of poorly sited coastal buildings may spend
more money on erosion control and erosion-related building repairs than they
spent on the building itself.

What Factors Constrain Siting Decisions?
Many factors affect and limit a home builder’s or owner’s ability to site
coastal residential buildings, but the most influential is probably parcel size,
followed by topography, location of roads and other infrastructure, regulatory
constraints, and environmental constraints. 

Given the cost of coastal property, parcel sizes are often small and owners
often build the largest building that will fit within the permissible
development footprint. Buyers frequently fail to recognize that siting decisions
in these cases have effectively been made at the time the land was platted or
subdivided, and that shoreline erosion can render these parcels unsuitable for
long-term occupation.

In some instances, however, parcel size may be large enough to allow a hazard-
resistant coastal building to be sited and constructed, but an owner’s desire to
push the building as close to the shoreline as possible increases the likelihood
that the building will be damaged or destroyed in the future.

Coastal Setback Lines – What Protection Do They Provide?
Many states require new buildings to be sited at or landward of coastal
construction setback lines, which are usually based on long-term, average annual
erosion rates. For example, a typical minimum 50-year setback line with an
erosion rate of 2.5 feet/year would require a setback of 125 feet, typically
measured from a reference feature such as the dune crest, vegetation line, or
high-water line.

Building at the 125-foot setback (in this case) does not mean that a building
will be “safe” from erosion for 50 years. 
--Storms can cause short-term erosion that far exceeds setbacks based on long-
term averages. 
--Erosion rates vary over time, and erosion could surpass the setback distance
in just a few years’ time. The rate variability must also be known to determine
the probability of undermining over a given time period.

What Should Builders, Designers, and Owners Do?
--Consult local and state agencies, universities, and consultants for detailed,
site-specific erosion and hazard information.
--Look for historical information on erosion and storm effects. How have older
buildings in the area fared over time? Use the experience of others to guide
siting decisions.
--Determine the owner’s risk tolerance, and reject parcels or building siting
decisions that exceed the acceptable level of risk.

Common Siting Problems
--Building on a small lot between a road and an eroding shoreline is a recipe
for trouble.
--Odd-shaped lots that force buildings close to the shoreline increase the
vulnerability of the buildings.
--Siting a building near the edge of a bluff increases the likelihood of
building loss, because of both bluff erosion and changes in bluff stability
resulting from development activities (e.g., clearing vegetation, building
construction, landscaping, changes in surface drainage and groundwater flow
patterns).
--Siting near a tidal inlet with a dynamic shoreline can result in the building
being exposed to increasing flood and erosion hazards over time.
--Siting a building immediately behind an erosion control structure may lead to
building damage from wave overtopping and may limit the owner’s ability to
repair or maintain the erosion control structure.
--Siting a new building within the footprint of a pre-existing building does not
guarantee that the location is a good one.

Siting should consider both long-term erosion and storm impacts. Siting should
consider site-specific experience, wherever available.