I am building a garden gate and frame out of PT lumber. The gate
frame is two 4x4s that hold a 4x4 cross member as so:
| |_____ground level_______
How can preserve the underground members so that they will last
longer? I will be putting a layer of gravel and some cement. Is there
a product such as cresote or tar that I can apply before I install the
when I install posts into the ground I wont use concrete.
if you use just a good gravel mix to pack in around the pole and you go a
good foot lower than the bottom of the post you will keep it from ever
getting water logged.
The gravel provides drainage. Contrete will wick moisture into the wood.
so even if there is only damp earth around the post the post will be wet all
the time and rot becomes a problem.
you can wrap your posts in 6mil poly too just like vapour barrier. I dont
If you have a good mix of Pea Gravel that is used over weeping tiles that
will keep the post solid and dry. Just tamp the gravel after every 6inches
or so as you put it in.
And just as a side note I usually make sure I have 4 feet of post in the
it just wont tip then.
It's probably not a big concern. This from the Southern Pine web site:
"How long does pressure-treated wood last? Currently available research
shows that wood that has been properly treated and installed for its
intended use can be expected to last for many decades.
Ongoing tests sponsored and monitored by the USDA forest Service's
Forest Products Laboratory confirm this finding. Test stakes of treated
wood have been buried in the ground at various locations, stretching
from the Mississippi Delta to the Canadian border. Data analysis
indicated that CCA-treated Southern Pine stakes in place since 1938
have shown no failures at chemical retention levels of 0.29 pounds of
preservative per cubic foot of wood, or higher."
If you use the typical .40 retention ACQ (CCA replacement), commonly
called ground contact, and don't bury a cut end, it should last decades
without further treatment. If you want higher levels of protection you
can purchase higher retention level treated wood.
If you're a belt and suspenders guy, and you want some added assurance,
you've answered your own question. A coating of roofing or flashing
cement will inexpensively waterproof the buried end of the post.
You may or may not know that there are "different" grades
of SYP pressure treated wood ???
Be sure to buy pt wood that is graded for "direct burial".
Not all Home Centers carry that grade.
They also recommend using a water proofing after the project
is completed, to help prevent checking.
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