FLOOD07643

• County: Statewide
• Basin: Statewide
• Title: Physical and Economic Feasibility of Nonstructural Flood Plain Management Measures
• Date: 3/1/1978
• Prepared For: US
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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CHAPTER 4
RAISINC EXISTlNC STRUCTURES

Description
Existing structures in flood hazard areas can often be raised in-place to a higher elevation to
reduce the susceptibility of the structure to flood damage. Specific actions required to raise a
structure include,
. Disconnect all plumbing, wiring, and utilities which cannot be raised with the structure.
. Place steel beams and hydraulic jacks beneath the structure and raise to desired elevation.
. Extend existing foundation walls and piers or construct new foundation.

. Lower the structure onto the extended or new foundation.
. Adjust walks, steps, ramps, plumbing, and utilities and regrade site as desired.
. Reconnect all plumbing, wiring and utilities.

. Insulate exposed floors to reduce heat loss and protect plumbing, wiring, utilities and
insulation from possible water damage.
These actions are intended to place the structure at a higher elevation at its existing site and to
protect plumbing and utilities below the first floor from water damage. Because the hazard is
not eliminated, but only the damage potential reduced, it is important that the potential for
flooding below the first floor be recognized in the raising. Where wave action is likely, the
structure should be raised an additional height above the design level to prevent inundation by
waves. Lateral stability of the structure should be insured by designing the foundation walls or
piers in a way that a hinge effect is not created between the superstructure and foundation.
Also, flood flow velocity should be accounted for in the design. All ground to house utility lines
(sewer, electrical, gas, water, telephone) should be protected against water, wind and extreme
temperature exposure which may be brought about by elevating the structure. Access to and
from the structure during high water should be insured when raising walks, steps, ramps, and
when regrading the site. This is important to insure occupant safety in the event the design flood
is exceeded. Figure 4-1 illustrates the concept of raising in-place.

Physical Feasibility
The principal consideration for physical feasibility is that the structure can be raised
economically. Generally, the technoiogy exists to raise almost any structure, even multistory
buildings, however, the more difficult the raising the more costly it becomes. Within the normal
range of expected annual flood damage, raising-in-place from a practical viewpoint is most
applicable to structures which can be raised with low cost conventional means. Generally, this
means structures, 1) which are accessible below the first floor for placement of jacks and beams,
2) which are light enough to be jacked with conventional house moving equipment, and 3)
which are small enough that they do not have to be partitioned. Wood frame residential and
light commercial structures with first floors above the ground (normally with an 18" crawl space
beneath the first floor) are particularly suited for raising. Wood frame structures with basements
below the first floor are also accessible and light weight, however, raising the superstructure

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