Q: What is FEMA?
The Federal Emergency Management Agency (FEMA), a former independent
agency, became a part of the new Department of Homeland Security
in March, 2003. FEMA is responsible for assisting communities
in responding to, planning for and recovering from natural
and other disasters in the US. One of the many functions of
this agency is to oversee the Technical Services Division,
which conducts hydrologic and hydraulic analyses to identify
flood hazards in communities throughout the United States
. Private engineering firms and Federal and State agencies,
under FEMA guidelines, perform many of those analyses.
the information gathered by the Technical Services Division,
FEMA publishes National Flood Insurance Program Maps or
FIRMs (Federal Rate Insurance Maps) that indicate a community’s
flood hazard areas and the degree of risk in those areas.
These maps are used by engineers, surveyors, and insurance
providers to complete FEMA Elevation Certificates.
Q: How does a surveyor determine
the elevations needed for a FEMA Certificate?
surveyor locates the nearest FEMA Benchmark to the property
being surveyed. Each benchmark has a known elevation,
with all benchmarks being relative to one another. (Theoretically,
a surveyor can use any known benchmark and obtain the
same elevations on the subject tract.) The surveyor
determines the subject tract elevations based on the known
of the benchmark using specially designed and calibrated
Q: What are the three types of FEMA certificates?
Section “C1” of the FEMA Certificate, there are three
checkboxes for each of the three types of Elevation Certificates.
They are “Construction Drawings”, “Building Under Construction” and “Finished
Construction”. The checkbox for the first two choices
states that a new elevation certificate is required
of the structure is complete.
Q: What are the three types of FEMA Elevation
Certificates needed by a builder?
first type is for “Construction Drawings” .
This certificate shows actual elevations determined
by the surveyor’s fieldwork, as well as proposed elevations
provided by the builder. The surveyor provides the
at “lowest adjacent grade” (LAG) and “highest adjacent
in the general area of the building line of the subject
tract. The builder provides the proposed “top of bottom
floor elevation), the “attached garage”, the “lowest
elevation of machinery and/or equipment servicing the
both the number and total area of permanent openings
(flood vents) on the structure. All elevations are
to a known benchmark, which is noted on the certificate.
The Base Flood Elevation (BFE) is also noted; and can
be found on the FIRM panels. The builder also provides
about the type of foundation planned, referencing FEMAs
building diagrams numbered 1-8. The “Construction Drawings” elevation
certificate is generally required by the City of Houston,
Bellaire, and City of West Univerisity Place for permitting
for all proposed structures in the 100-year
second elevation certificate needed is for “Building
Under Construction”. The elevations needed
are the same as for the “Construction Drawings” certificate,
but at this stage, the elevations are now actual numbers
numbers. These elevations are generally obtained when
the surveyor performs the form survey.
Under Construction” elevation certificate is generally
required by the City of Houston,
Bellaire, and City of West Univerisity Place before
a concrete slab can be
third and final elevation certificate needed is for “Finished
Construction”. In order for the certificate to be submitted
for flood insurance, the structure needs to be near
completion with all flood vents installed and the concrete
the HVAC system in place. This certificate is required
in order to obtain flood insurance. Either/or the lender
Title Company usually require it as well.
What are the City of Houston requirements in regards to finished
floor elevations for new construction for property in the
100-year flood plain?
City requires that the finished floor elevation, attached garage
elevation, and elevation of machinery servicing equipment
be no less than 1 foot (12") above the Base Flood Elevation
as determined from the FIRMs.
: The FIRM shows my lot is in the mapped floodplain,
but when I had my elevation certificate done, my house
is above the
Base Flood Elevation (BFE). Doesn’t this mean I’m
out of the floodplain?
Building above the BFE will certainly
help keep the cost of flood insurance down, as well as being
at resale, but you cannot build “outside of the floodplain.” The
various floodplain zones are determined by hydrologic
and hydraulic analyses by private engineering firms
and State agencies, under FEMA guidelines. To be considered
outside of the floodplain would require a Letter of
Map Change of which there are six (6) different types,
a change in
the flood zone determination when FIRMs are updated
and reissued. To summarize: you can build above the
base flood elevation, but this does not mean that you
are out of the
What year were the last FEMA maps issued for the Houston
As a general rule, surveyors in the
Greater Houston area reference floodplain elevations based
on FIRMs dated April
20, 2000. These maps are based on 1929 North American
Datum (1929 NAVD) with a 1973 adjustment.
: Many areas of the city flooded after Tropical Storm
Allison in 2001 that were not considered to be
in a “flood zone”.
Is FEMA planning to update and revise the maps for
FEMA is in the process of updating some of the FIRM
panels for the Houston area. The new maps have not
as of yet, so we continue to use the April 20, 2000
Why is there a different adjustment applied to FIRM benchmarks
in the Brays Bayou Watershed?
Lichliter/Jameson & Associates,
(LJA) performed a hydraulic study in this area
in 1994 at the request
County Flood Control District. The FIRM panels for
the area were
based on this study, typically referred to as the 1987
adjustment. The confusion occurs when surveyors reference
on these panels, which are on the 1973 adjustment.
Therefore, surveyors use a conversion table that shows
from the 1973 benchmark elevations to the 1987 elevations
established by LJA. Essentially what has happened is
that the land in this area has subsided, which is reflected
on the FIRM panels, but not in the benchmarks printed
I want to build an addition to my house, which is located
in the 100-year flood plain. I was told that there are
some limitations associated with improvements for
homes in the
flood plain. What are they?
City of Houston will not grant a building permit for
improvements if the cost of those improvements
of the appraised value of the current structure.
I was planning to build a new home with a “slab on grade
foundation” The City has just rejected my permit
for this type of foundation and informed me that
I must build a
raised slab with flood vents. How did they determine
areas that in Zone A or Zone AE, if the “lowest adjacent
grade” (LAG) is more than 24” below the Base Flood
Elevation (BFE), the City of Houston will require
to conform to FEMAs Diagram 8 (pier and beam with
or Diagram 5 (elevated on piers, posts or columns).
This is sometimes the case in the Brays Bayou Watershed,
occasionally in the Houston Heights.