Information for Builders
Builders and contractors have some pretty big shoes
to fill. They are the critical link between the designers, the
local code official, and the owners or residents of the building.
A builder's reputation is usually based on the quality of the
finished product, so the best builders rely on AWPA to write the
standards for the treated wood products they use in their
Why should I require wood treated to
Besides the fact that most architects and engineers
specify AWPA Standards for treated wood, AWPA Standards are the
only wood treatment standards listed directly in the IBC and
IRC. AWPA has over 100 years of history in developing
treated wood standards. Our standards are
developed in an open, consensus-based, ANSI accredited process
to ensure stringent review of performance data while providing
due process for all participants. Most of the world's
experts in wood protection actively serve on our Technical
Committees - a level of expertise unmatched elsewhere.
The building inspector says I need to
use a preservative to coat the cut ends of treated wood.
What should I use?
The inspector is probably referring to AWPA Standard
M4, which allows the use of borates for interior uses, or copper
naphthenate for primarily exterior uses. The availability
of copper naphthenate varies widely at paint, hardware, and
building supply stores. The 2% copper solution may be
purchased online from Copper
Care Wood Preservatives, under the trade name "Tenino".
According to M4, thick sapwood species that appear to be well
treated and contain little or no heartwood may not require field
treatment, although it is a recommended practice. Contact
us for more information.
Can I use a brush-applied or sprayed
preservative instead of pressure treated wood?
A brush on or spray on preservative is just a surface
treatment. When wood is put into service it is immediately
exposed to the rigors of water, decay fungi colonization,
termites and UV and visible violet light degradation. The wood
will at first check (cracks a long the grain) at a microscopic
level, and later into increasingly wider checks. Although the
first openings are microscopic they are more than adequate to
allow these wood destroying fungi past the paint on surface
protection to the unprotected wood just below the surface where
once established will ultimately make the wood unfit for the
purpose it was installed. If such a “surface” treatment existed
it would be marketed as well as acknowledged by the Forest
Products Laboratory or AWPA. On pressure treated wood penetrate
below the surface for more thorough protection of the wood.
Is "mold resistant" treated wood the
same as pressure treated wood?
Mold resistant wood is specifically designed to do what
it says…resist mold growth. It is not a replacement for
pressure treated wood. Mold, although unsightly and a
potential source of airborne toxins is not in itself a very
great threat to wood structure and the soundness of wood members.
Mold resistant wood should not be used outdoors or in areas
expected to be in contact with soil or masonry such as sill
plate. Pressure treated wood has various “Use Categories” that
can be viewed in other parts of this website that identify the
proper use of matching an application with the right level of
Can wood be preservative treated and fire
retardant treated at the same time?
Under AWPA Standards, preservative treatment and fire retardant
treatment are two different technologies. Preservatives
are expected to protect the wood from decay fungi and termites
every day over a long period of time. Fire retardants are
expected to remain in the wood and protect it from a one-time
event. Some preservatives do impart a degree of fire
retardancy, and some fire retardants can act as preservatives to
some extent. At this time, there is only one AWPA
standardized product which may be used both as a fire retardant
and wood preservative, and it is only listed for interior uses.
Apart from this, fire retardant treated wood should
not be used where preservative treatment is required, nor should
preservative treated wood be used when fire retardant treated
wood is required.
What kind of fasteners and connectors
should I use in pressure treated wood?
AWPA's test methodologies are used to determine
relative corrosion rates, and cannot be used to estimate
corrosion of fasteners and connectors in the field. For
this reason, we suggest using fasteners that meet the
requirements of the major model building codes, which specifies
hot dip galvanized steel, stainless steel, silicon bronze, or
copper fasteners. The model codes also allow for the use
of mild steel fasteners for wood treated with inorganic boron
(SBX) in dry environments. There are literally hundreds of
fastener coatings available, so it is important to follow the
fastener manufacturers recommendations regarding compatibility
of their fasteners with pressure treated wood.