I'm about to pour some footings for a covered deck. I'm going to be putting 6x6 posts on top of concrete piers, but before I cut my sauna tubes, how high should my pier project above grade? Is there a minimum height that's pretty much standard, or can I make the top of my pier be right at ground level?
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Are your 6X6s pressure treated? – Jack Oct 17 '19 at 1:51
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Most likely, but haven't ruled out using 2x6's and wrapping and cladding them after. – ShemSeger Oct 17 '19 at 2:29
If your posts are pressure treated, you can set the concrete level to grade. If the posts are not pressure treated, I would set the top of concrete at 8" above grade. more would not hurt. Also use metal fasteners that hold the post up off the concrete 1" in either case.
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1Many metal post bottoms will have this feature. It is to keep the wood from having direct contact with the concrete which holds water much more readily than the steel plate that helps create the airspace. Harboring moisture advances the decay of wood. – Jack Oct 17 '19 at 13:58
There are two grades of pressure treated lumber: 1) Above Ground Use, and 2) Ground Contact.
1) Above Ground Use is used for deck railings, building wall sole plates, etc.
2) Ground Contact lumber can be on the ground or in the ground.
If your concrete piers are within 6” of the ground, they are considered “Ground Contact Use” by the Code. Ground contact pressure treated lumber should have a tag stamped to it. It’s best to have water drain away and not have any standing water.
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In my experience, the common grades are "ground contact" (.40) and "foundation grade" or "immersion grade" or whatever (.60). In other words, all PT lumber is rated for above-grade contact. – isherwood Oct 17 '19 at 16:39
I like to put bring the footers 6-8 inches above grade. I go on the higher side if its on a slope. Much more than that and you are buying a lot of concrete.
