FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

Volume II DESIGNING THE BUILDING 9
8. The requirement for separation of the foundation elements between townhouse units makes structural
rigidity in the direction parallel to the shore more difficult to achieve. If the houses in Figure 9-32 were
in a seismic hazard area, the designer could decide to place diagonal bracing parallel to the shore (i.e.,
perpendicular to the primary flood flow direction) or use more closely spaced and larger piles. Diagonal
bracing would provide rigidity but would also create an obstruction below the DFE. The design
professional should consult FEMA NFIP Technical Bulletin 5 (FEMA 2008c) for information about
the types of construction that constitute an obstruction.
One solution to some of the issues illustrated by Figure 9-32 would be to use two parallel independent walls
to provide the required fire separation between units. Each wall could be attached to the framing system
of the unit on one side of the separation and supported by a beam running perpendicular to the shore and
bearing on the open foundation of that unit.
9.4.5 Corrosion
Modern construction techniques often rely heavily on metal
fasteners and connectors to resist the forces of various coastal
hazards. To be successful, these products must have lifetimes
that are comparable to those of the other materials used for
construction. Near saltwater coastlines, corrosion has been
found to drastically shorten the lifetime of standard fasteners
and connectors. Corrosion is one of the most underestimated
COASTAL CONSTRUCTION MANUAL
Figure 9-32.
Townhouse framing
system
CROSS REFERENCE
For additional information about
corrosion of metal connectors in
coastal construction, see FEMA
NFIP Technical Bulletin 8-96.
hazards affecting the overall strength and lifetime of coastal buildings. To be successful, hazard-resistant
buildings must match the corrosion exposure of each element with the proper corrosion-resistant material.
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