I need to install a treated 4X4 as a gate post through a slab (yet to be
I can't surface install on one of those galv brackets, because the 4X4 needs
a gate and small fence section.
Would the 4X4 last better if cast right into concrete, or should I make a
well for it, filled with compacted aggregate?
The bottom of an aggregate well can connect to grade for drainage.
a pressure treated 6"x6" was too small it leans after 10 years on mine
which is holding up a heavy steel framed wooden driveway gate on
next time i would secure an 8x8 instead. we installed as if it is a
fencepost in your soil and climate and frost level requirements first.
then installed the driveway slab. but next time we'll try a wheel on
that heavy gate to roll on the driveway and take some of the gate
bill allemann wrote:
The weight of the gate isn't very much, just 36" wide wood construction,
pretty much like a door.
And I could hide a guy wire along the adjoining section of fence to help
with the weight of the gate.
also, the concrete won't move. it will be part of a fairly large slab.
I'm mainly concerned about whether direct contact with concrete is bad
rotting of the treated wood.
Why not support the post with an eyebolt and cable arrangement? It wouldn't
be hard and would look perfectly fine in that situation. Bury an eyebolt in
a fencepost size chunk of concrete - just like any other post, then attach
the cable to the 4x4 or 6x6 and apply tension with a turnbuckle or similar
The post is gonna sag regardless of how much concrete you sink it into - it
has to support a cantilever load from the gate. The cable would attach to
the top of the gatepost and transfer that load to the cable and its
foundation. the loading would no longer be acting perpendicular to the
support and the whole setup would last much longer.
Just spend a couple extra bucks and make that one 4x4 a .60 pcf (or .80
pcf if you can find it). Paint the bottom with some tar or creosote,
and make sure to put a cap on the top. Go ahead and sink it right into
the concrete. Slope the concrete slightly away from the post. It'll
The other posters are correct; if the gate has substantial weight and
you are cantilevering the entire weight on one 4x4, it will bend over
time (probably sooner rather than later). In my prior post I was
addressing the issue of wood deterioration only.
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