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UFPI.COM
THIS DOCUMENT IS FOR INFORMATIONAL PURPOSES ONLY AND NOTHING HEREIN SHALL BE CONSTRUED AS GRANTING ANY ADDITIONAL WARRANTIES OTHER THAN
THE TERMS OF THE EXPRESS WRITTEN WARRANTIES FOR PROWOOD AND UFP TREATED REFERENCED HEREIN. ANY ADDITIONAL WARRANTIES, EXPRESS OR IMPLIED,
ARE HEREBY EXPRESSLY DISCLAIMED.
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TECHNICAL BULLETIN
UNDERSTANDING PRODUCT USE OF PRESSURE-TREATED LUMBER
KEY FACTS:
• Wood swells as its moisture content goes from zero (bone dry) to about 30% (referred to as “fiber saturation”)
• The amount of swelling is solely a characteristic of that individual piece of wood
• Wood will achieve equilibrium with its environment over time, with most outdoor wood reaching a moisture content of about 12%
• Most of our treated wood will be at fiber saturation when purchased
• ProWood® KDAT will be purchased with about 19% moisture content.
Wood also picks up water during the life of the project when exposed to rain or standing water, then dries out again
as conditions permit. As it does, it will swell and shrink. This wet-dry (swell-shrink) cycle is part of the natural weathering
of any wood and can contribute to checking and splitting, among other undesirable conditions.
WOOD TREATMENT FROM OUTSIDE TO INSIDE
When pressure-treated products are machined (cross cut, ripped or machined), unprotected or weakly protected areas
can be exposed, lessening the wood’s ability to resist attack from decay fungi or termites. Here’s why…
ProWood® products are pressure treated in a process that forces chemical preservatives deep into the wood through
the application of vacuum/pressure inside a closed cylinder. The preservative starts on the outside and pushes its way
deep into the wood. Generally speaking, the sapwood is penetrated but the heartwood is not penetrated. Industry
standards clearly define the required preservative penetration into the wood, as well as the way in which each batch
must be tested after treating.
Southern Pine is the predominant species used for ProWood® products. Southern Pine has many desirable qualities.
It’s a strong, renewable building material and very receptive to treatment. This species is comprised mainly
of treatable sapwood with relatively small amounts of heartwood. Often the sapwood adjacent to the heartwood can
be dicult to penetrate during the treating process, a fact reflected in the industry standards.
Finally, as the treating solution makes its way through the wood fiber toward the middle, some preservative is deposited
in a higher concentration on the outside compared to the center.
The purpose of this information is to help users of our pressure-treated products understand why anytime the product
is machined, care should be taken. First, one should be aware of the impact machining has on the warranty. The use of
a brush on wood preservatives during construction, and the extra care required by these exposed surfaces during the
life of the structure, should be considered. Finally, do not place the exposed surface in direct contact with the ground
or in similar environments.
WHY ROT AND TERMITES CAN’T GET A FOOTHOLD
One of the primary ways our preservatives protect wood from decay fungi is by making it very dicult for spores to take
root on the wood surface. However, if the decay fungi has settled into an untreated piece of wood that is touching a piece
of treated wood, the fungi are better able to challenge—and maybe even overcome—the protection oered by the
preservative treatment. There are a couple ways this can happen. If our product is in contact with an untreated piece of wood,
the fungi may attack the treated product. Similarly, if aboveground treated wood is used in contact with the ground, it may
succumb due to reasons described earlier. This piece can then threaten adjacent pieces of treated wood, even though they
were used in the correct application (i.e., aboveground treated wood used in an aboveground application).
The situation is similar for termite attack. Untreated wood can draw termites to the properly treated product en masse and
make it more likely for them to penetrate the protection aorded by the preservative treatment.
THE SHRINKING OF DECK BOARDS THAT RESULTS IN GAPS IS NOT COVERED BY
WARRANTY. THIS SHRINKING SHOULD BE ACCOUNTED FOR DURING CONSTRUCTION.
WARRANTY TIP
IF OUR TREATED WOOD IS CUT LENGTHWISE OR SURFACED, POSSIBLE DAMAGE
RESULTING FROM DECAY FUNGI OR TERMITE ATTACK IS NOT COVERED BY WARRANTY.
WARRANTY TIP
IF OUR TREATED WOOD IS IN DIRECT CONTACT WITH UNTREATED WOOD OR
IMPROPERLY USED WOOD, POSSIBLE DAMAGE FROM DECAY FUNGI OR TERMITE
ATTACK IS NOT COVERED BY WARRANTY.
WARRANTY TIP