Home Builder’s Guide to Coastal Construction
FEMA 499/June 2005
Technical Fact Sheet No. 12
Purpose: To provide basic information about pile design and installation.
--Use a pile type that is appropriate for local conditions.
--Have piles designed by a foundation engineer for adequate layout, size, and
--Use installation methods that are appropriate for the conditions.
--Brace piles properly during construction.
--Make accurate field cuts, and treat all cuts and drilled holes to prevent
--Have all pile-to-beam connections engineered, and use corrosion-resistant
hardware. (See Fact Sheet No. 8.)
Treated wood piles are the most common type of pile used in coastal
construction. They can be square or round in cross section. Wood piles are
easily cut and adjusted in the field and are typically the most economical type.
Concrete and steel can also be used but are less common. Concrete piles are more
expensive, but they are stronger and more durable. Steel piles are rarely used,
because of potential corrosion problems.
Pile Size and Length
Pile size and length are determined by the foundation engineer. Specified
bearing and penetration requirements must be met. Piles should have no less than
an 8-inch tip diameter; minimum timber size should be 8x8. The total length of
the pile is based on code requirements, calculated penetration requirements,
erosion potential, Design Flood Elevation (DFE), and allowance for cut-off and
beam width (see figure at right).
Note: Misaligned piles lead to connection problems. See Fact Sheet No. 13 for
information about making connections t misaligned piles.
The pile layout is determined by the foundation engineer. Accurate placement and
correction of misaligned piles is important. Pile placement should not result in
more than 50 percent of the pile cross-section being cut for girder or other
connections. Verify proper pile locations on drawings before construction and
clarify any discrepancies. Layout can be done by a licensed design professional,
a construction surveyor, the foundation contractor, or the builder. The layout
process must always include establishing an elevation for the finished first
floor. Construction of the first-floor platform should not begin until this
elevation is established (see Fact Sheet No. 4).
Piles can be driven, augured, or jetted into place. The installation method will
vary with soil conditions, bearing requirements, equipment available, and local
practice. One common method is to initially jet the pile to a few feet short of
required penetration, then complete the installation by driving with a drop
Pile bracing is determined by the foundation engineer. Common bracing methods
include knee and diagonal bracing. Bracing is often oriented perpendicular to
the shoreline so that it is not struck broadside by waves, debris, and velocity
flow (see figure at right). Temporary bracing or jacking to align piles and hold
true during construction is the responsibility of the contractor.
--Knee Bracing: 3x or 4x treated wood members at 45 degrees to pile and located
approximately 4 feet below end of pile (see Fact Sheet No. 13)
--Diagonal Bracing: 2x or 3x treated wood members, or steel rods, attached near
top of pile and near ground
To avoid costly pile repairs or replacement, measure, locate, and double-check
the required pile cutoff elevations before cutting off piles.
Field Cutting and Drilling
A chain saw is the common tool of choice for making cuts and notches in wood
piles. After making cuts, exposed areas should be field-treated to prevent
The connection of the pile to the structural members is one of the most critical
connections in the structure. Always follow design specifications and use
corrosion-resistant hardware (see Fact Sheet Nos. 8 and 13).
Verification of Pile Capacity
Generally, pile capacity for residential construction is not verified in the
field. If a specified minimum pile penetration is provided, bearing is assumed
to be acceptable for the local soil conditions. Subsurface soil conditions can
vary from the typical assumed conditions, so verification of pile capacity may
be prudent, particularly for expensive coastal homes. Various methods are
available for predicting pile capacity. Consult a foundation engineer for the
most appropriate method for the site.
American Forest and Paper Association (AF&PA). National Design Specification for
Wood Construction. (www.afandpa.org)
American Society for Standards and Testing (ASTM). Standard Specification for
Round Timber Piles, ASTM D25. (www.astm.org)
American Wood-Preservers Association (AWPA). All Timber Products – Preservative
Treatment by Pressure Processes, AWPA C1-00; Lumber, Timber, Bridge Ties and
Mine Ties – Preservative Treatment by Pressure Processes, AWPA C2-01; Piles –
Preservative Treatment by Pressure Process, AWPA C3-99; and others.
Pile Buck, Inc. Coastal Construction. (www.pilebuck.com)