SECTION 2: SERVICE CONDITIONS FOR USE CATEGORY DESIGNATIONS
Jurisdiction: AWPA Technical Committees T-2, T-3, T-4, and T-8
The following is a breakdown of the Use Categories used by AWPA to describe the exposure conditions that wood may be subject to in
service. This is also given in table form on the next page to summarize the major differences between Use Category groupings.
UC1 INTERIOR/DRY
Wood and wood based materials used in interior construction
not in contact with the ground or foundations. Such products
are protected from weather and interior sources of water such
as leaking plumbing, condensate, pools and spas. Examples
are interior furniture, construction furnishings, and millwork.
UC2 INTERIOR/DAMP
Wood and wood based materials used for interior construction
that are not in contact with ground, but may be subject to
dampness. These products are continuously protected from the
weather but may be exposed to occasional sources of moisture.
Examples are interior beams, timbers, flooring, framing,
millwork and sill plates.
UC3 ABOVE GROUND (Exterior)
UC3A ABOVE GROUND Protected -- Wood and wood-
based materials used in exterior construction that are coated
and not in contact with the ground. Such products may be
exposed to the full effects of weather, such as vertical
exterior walls or other types of construction that allows
water to quickly drain from the surface.
coated millwork, siding and trim.
Examples are
UC3B ABOVE GROUND Exposed -- Wood and wood
based materials used in exterior construction and not in contact
with the ground. Materials do not require an exterior coating,
but may be finished to achieve a desired aesthetic appearance.
Materials are used for a variety of applications in either
horizontal or vertical positions such as decking, sills,
walkways, railings and fence pickets. Note: Retentions above
the minimum specified for materials in this use category may
be required for products such as crossarms where the
individual components are difficult to maintain, repair or
replace and are critical to the performance and safety of the
entire system.
UC4 GROUND CONTACT
UC4A GROUND CONTACT General Use -- Wood and
wood-based materials used in contact with the ground, fresh
water, or other situations favorable to deterioration.
Examples are fence posts, deck posts, guardrail posts,
structural lumber, timbers and utility poles located in regions
of low natural potential for wood decay and insect attack.
UC4B GROUND CONTACT Heavy Duty -- Wood and
wood-based material used in contact with the ground either
in severe environments, such as horticultural sites, in
climates with a high potential for deterioration, in critically
important components such as utility poles, building poles
and permanent wood foundations, and wood used in salt
water splash zones. This category includes utility poles used
in moist temperate climates.
UC4C GROUND CONTACT Extreme Duty -- Wood and
wood based materials used in contact with the ground either
in very severe environments or climates demonstrated to
have extremely high potential for deterioration, in critical
structural components such as land and fresh water piling
and foundation piling, and utility poles located in semi-
tropical or tropical environments.
UC5 MARINE USE
UC5A MARINE USE Northern Waters -- Wood and
wood based materials exposed to salt and brackish water
which includes Long Island, NY and northward on the east
coast and north of San Francisco on the west coast to the
extent that the marine borers can attack them. This includes
areas where Limnoria quadripunctata is present, but lacks
those borers listed under UC5B and UC5C. This includes
piling and bracing, bulk-heading or other construction that is
actually exposed at some time during the year to salt water.
UC5B MARINE USE Central Waters -- Wood and wood
based materials exposed to salt and brackish water south of
Long Island, NY to the southern border of Georgia on the
east coast and south of San Francisco on the west coast to
the extent that the marine borers can attack them. This
includes areas where creosote tolerant Limnoria tripunctata
is present, but lacks those borers listed under UC5C. This
includes piling and bracing, bulk-heading or other
construction that is actually exposed at some time during the
year to salt water.
UC5C MARINE USE Southern Waters -- Wood and
wood based materials exposed to salt and brackish water
south of Georgia and along the gulf coasts in the eastern
U.S., as well as Hawaii and Puerto Rico, to the extent that
the marine borers can attack them. This includes areas
where Martesia and Sphaeroma are present. This includes
piling and bracing, bulk-heading or other construction that is
actually exposed at some time during the year to salt water.
UCF FIRE RETARDANT
UCFA FIRE RETARDANT Interior -- Wood and wood
based materials intended for fire protection and used in
interior construction where wood material is not in contact
with the ground and is protected from exterior weather.
UCFB FIRE RETARDANT Exterior -- Wood and wood
based materials intended for fire protection and used in
exterior construction that is not in contact with the ground or
with foundations, but may be exposed to full effects of
weather such as intermittent rain, dew, sunlight and wind.
Materials are applied to vertical, exterior walls, inclined roof
surfaces or other types of construction that allow water to
quickly drain from the surface.
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U1-15
USE CATEGORY SYSTEM: USER SPECIFICATION FOR TREATED WOOD
Page 3 of 66
© 2015
TABLE 2-1 SERVICE CONDITIONS FOR USE CATEGORY DESIGNATIONS
USE
CATEGORY
UC1
INTERIOR/
DRY
UC2
INTERIOR/
DAMP
UC3A
ABOVE
GROUND
Protected
UC3B
ABOVE
GROUND
Exposed
UC4A
GROUND
CONTACT
General Use
UC4B
GROUND
CONTACT
Heavy Duty
UC4C
GROUND
CONTACT
Extreme Duty
UC5A
MARINE USE
Northern
Waters
UC5B
MARINE USE
Central Waters
SERVICE CONDITIONS
Interior construction
Above Ground
Dry
Interior construction
Above Ground
Damp
Exterior construction
Above Ground
Coated & rapid water runoff
Exterior construction
Above Ground
Uncoated or poor water run-off
Ground Contact or Fresh Water
Non-critical components
USE ENVIRONMENT
Continuously protected from
weather or other sources of
moisture
Protected from weather, but may be
subject to sources of moisture
COMMON AGENTS OF
DETERIORATION
Insects only
TYPICAL
APPLICATIONS
Interior construction and
furnishings
Decay fungi and insects
Interior construction
Exposed to all weather cycles, not
exposed to prolonged wetting
Decay fungi and insects
Coated millwork, siding and
trim
Exposed to all weather cycles
including prolonged wetting
Decay fungi and insects
Exposed to all weather cycles,
normal exposure conditions
Decay fungi and insects
Ground Contact or Fresh Water Exposed to all weather cycles, high Decay fungi and insects with
Critical components or
difficult replacement
decay potential
includes salt water splash
increased potential for
biodeterioration
Ground Contact or Fresh Water
Critical structural components
Exposed to all weather cycles,
severe environments
extreme decay potential
Decay fungi and insects with
extreme potential for
biodeterioration
UC5C
MARINE USE
Southern
Waters
UCFA
FIRE
RETARDANT
Interior
UCFB
FIRE
RETARDANT
Exterior
Salt or brackish water
and adjacent mud zone
which includes Long Island,
NY and northward, north
of San Francisco
Salt or brackish water
and adjacent mud zone
south of Long Island, NY
to the southern border of
GA, south of San Francisco
Salt or brackish water
and adjacent mud zone
South of GA, Gulf Coast,
Hawaii, and Puerto Rico
Fire protection as required
by codes
Above Ground
Interior construction
Fire protection as required
by codes
Above Ground
Exterior construction
Continuous marine exposure
(salt water)
Salt water organisms
Decking, deck joists, railings,
fence pickets, uncoated
millwork
Fence, deck, and guardrail
posts, crossties & utility poles
(low decay areas)
Permanent wood foundations,
building poles, horticultural
posts, crossties & utility poles
(high decay areas)
Land & Freshwater piling,
foundation piling, crossties &
utility poles
(severe decay areas)
Piling, bulkheads, bracing
Continuous marine exposure
(salt water)
Salt water organisms
Including creosote tolerant
Limnoria tripunctata
Piling, bulkheads, bracing
Continuous marine exposure
(salt water)
Continuously protected from
weather or other sources of
moisture
Salt water organisms
Including
Martesia, Sphaeroma
Fire
Piling, bulkheads, bracing
Roof sheathing, roof trusses,
studs, joists, paneling
Subject to wetting
Fire
Vertical exterior walls, inclined
roof surfaces or other
construction which allows water
to quickly drain