Building Requirements in Special Flood Hazard Areas
Thurston County regulates construction in
Special Flood Hazard Areas in
order to protect lives, property, and the environment. These areas
include locations that experience river flooding and groundwater
Some of the regulations are found within
Thurston County's Building Code; others
are found within the county's
Critical Areas Ordinance.
This page summarizes key provisions of both codes.
What is a Special Flood Hazard Area?
A Special Flood Hazard Area is any area:
- Subject to a base of one-hundred year flood (areas of special
flood hazard are shown on a flood hazard boundary map or Flood
Insurance Rate Map as Zone A, AO, A1-30, AE, A99, AH, VO, V1-30, VE,
- High Ground Water Flood Hazard Areas Resource Map on file with
the Resource Stewardship Department.
- Highest known recorded flood elevation.
Click here for a description of some
of the tools Thurston County uses to determine which properties are in a
Special Flood Hazard Area.
Thurston County participates in the
National Flood Insurance Program
which means our building standards for Special Flood Hazard Areas are
based upon federal floodplain regulations set by FEMA.
applying for a building permit in a Special Flood Hazard Area,
applicants are required to provide a pre-construction
elevation certificate that
confirms the vertical height requirement for flood protection.
- The building plans must conform to the Thurston County
requirements for construction in Special Flood Hazard Areas (see
below). Among other things, the floor elevation of the new home must
be 2 feet above the base flood elevation as established by a
professional surveyor. Floor elevation will be verified during the
home’s floor framing or manufactured home’s blocking inspection.
Also, the foundation must contain flow through vents for the passage
and draining of flood water.
- An as-built elevation
certificate must be completed by a professional surveyor. This
is additional information gathered from the surveyor’s inspection of
the completed home.
- Proof of flood insurance for the home must be submitted to the
Thurston County Permit Assistance Center.
- The owner must subscribe to the Thurston County flood warning
system. This subscription is free and can be arranged by calling
Building Requirements in Special Flood Hazard
Thurston County participates in the National Flood Insurance Program,
which means our building requirements (codes) for Special Flood Hazard
Areas are based upon federal floodplain regulations set by FEMA.
- In Special Flood Hazard Areas, the
lowest floor (including basement) and all flood-susceptible
materials must be elevated at least 2 feet above the base flood
elevation as established by a professional surveyor. Floor elevation
will be verified during the home’s floor framing or manufactured
home’s blocking inspection. In high-groundwater areas, construction must also be set
back 50 feet from the area that experiences open water.
- The foundation must contain flow through vents for the
passage and draining of flood water.
- To see Thurston County's building standards for Special Flood
Hazard Areas, visit
section 14.38.050 of Thurston County Code
Title 14. These standards may reference floodplain zones designated by
FEMA, such as "Zone A" or Standards may vary depending on which
floodplain zone a property is in. Click
here for a description.
- FEMA provides technical bulletins to help property owners comply with
local codes. Click here for a list.
Also see page 35 of the
standards in Special Flood Hazard Areas are complicated, but you don't
need to do it alone! The Permit Assistance Center is here to help.
Click here to contact residential plan reviewer Tim Rubert at
firstname.lastname@example.org or call (360) 786-5490.
How is "Base Flood Elevation" Established?
Base Flood Elevations are established using several different sources,
including FEMA maps. Click here for a description. Building
applicants don't figure out this information on their own; rather,
Thurston County requires applicants to submit a
pre-construction Flood Elevation
Certificate when applying for a permit.
Please be advised that Thurston County's
Critical Areas Ordinance
and Shoreline Master
Program also establish buffers along rivers, streams and marine
For questions about building in a Special Flood Hazard Area, contact
Tim Rubert at 754-3355 ext. 6647 or e-mail