How to prevent a 4X4 post from rotting in the ground is one of the three ways to protect a wooden post.

The beds are in the vegetable garden.My gardener replaced some wood framed raised garden beds with this stone border.I asked them to sink a 4X4 post to support the shade sail.They put the post where I needed it.

I wasn't aware that 6 inches of this post was going to be sitting in moist soil.

The concrete stops at the ground level, not the soil level that will be the top of the raised bed.Before I fill in the rest of the dirt and restore the irrigation, I want to protect this post from rotting at the base above the concrete and below the soil line.

I have some leftover concrete.I'm wondering if I should raise the concrete level by placing a small square around it.Is it possible to paint on Thompson's Water Seal?I don't want to use anything that might be poisonous if I eat it.

Concrete is used to counterbalance the forces on the other side of the post.Any type of rot resistance is created by zero.The rot resistance has to be inside the wood.It is either pressure or SYP.It's natural, like cedar or redwood.If that is true, and not a dyed substitute, then it will be resistant as anything else you'd use.

The terminology is resistant and not proof.There is no wood that is rot proof.If the situation is important, you should use power coated or galvanized steel.

I agree.It doesn't add any benefit to rot resistance because concrete is porous and will absorb water just as easily as the soil.The wood can be treated with aPreservative that will extend its resistance.You should be able to find at least a couple of no/low VOC, non-toxic wood sealers for sale at Lowe's or Home depot.

Thank you for the information!Yes, it is real.I suppose I should coat the entire post if I brush it with a water seal.If I go the lazy route and just seal the bottom half, there will be no way to get out of it.Is it true that I am mistaken?

It is too late to do anything.There is a section of the post in the ground.Nothing will be done to prevent that.Usually, in a situation like this, one would put gravel in the bottom of the hole before pouring in concrete, which will allow some water to drain out and help the rotting process.A pressure treated post is superior to natural wood.It will take a number of years for you to worry about anything since you have a redwood post.

Concrete in contact with wooden posts causes rot.Posts can be set in gravel or crushed stone.

Boric acid rods can be put in the wood to prevent rot.As they wear out, you would have to add new ones.

There is a System-Three-4-Inch-12-Pack on Amazon.

I use post anchors to hold wood above the ground.The clothesline is 30 years old.I replaced one gate post about 20 years ago and used them for the rest of the fence posts a few years later.

The fence needs to be connected to the house or garage to give it stability.If you need a permit, people do this all the time.The fence posts are poor at resisting wind loads because they are connected at the bottom.You've been lucky.

In use and empty, the clothesline is a single post.The fence is 3' tall and has 50% coverage with 2.5' posts so there is very little worry of wind damage.Thanks so much for the information, it's not up to code.