I need to install a treated 4X4 as a gate post through a slab (yet to be poured). I can't surface install on one of those galv brackets, because the 4X4 needs to support 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.
Thanks, Bill
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 hinges. 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 weight.
bill allemann wrote:
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 arrangement.
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.
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 regarding rotting of the treated wood.
Bill
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 last forever.
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.
PT wood can be installed with concrete poured around it. Just make sure the bottom of the post is on bare ground and not on concrete so you won't have a water retention problem with the post.
Bob
A 4x4 sounds too small. I recommend a 6x6 post unless your gate is small. There should be concrete between the posts or a beam overhead--the gate will tend to pull the posts together.
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