Replacing Rotten Fence Posts (first step in fixing a wooden fence)

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Does your fence have rotten wood posts? Does it sway in the wind and threaten to tumble over? That’s what I was dealing with, and in this article I’ll describe the steps I took in replacing rotten fence posts (the first step in fixing up a broken old privacy fence).

This article on replacing rotten fence posts will be the first article in a series of posts where I document how I replaced the broken privacy fence at my rental house.

Disclaimer: I am not a carpenter by trade. I did a lot of research before I tackled this project, but as you know, opinions are a dime a dozen on the internet. So don’t take this as “expert opinion” take it as a personal explanation of how I fixed my rotten fence posts. But in case it helps you or inspires you, I’ve documented what I did. And I did it by myself: I didn’t have a crew to help me. So I’m not to be held liable for any mishaps that may occur as a result of you following what I did.

Before Shots of the Broken Privacy Fence

Below is a photo of the fence before I started working on it. It was in pretty rough shape. And not only was it unattractive, but it could have fallen over in a stiff breeze.

You can see the fence was being held together with a ratchet strap, and pieces of scrap wood. (I did what I needed to prevent it from falling before I could replace it.)

The rotten fence posts in a concrete footing

The major problem with the fence, and the reason it wasn’t solid was that the fence posts were rotten at the base. In the picture below you can see I detached the fence railings from the post and the post snapped right off and fell to the ground.

I decided to remove and replace just one fence post at a time. 

That way I could keep my new post in line with the existing posts, and so that I could patch the fence up at the end of the day so my tenant had a functional fence to protect her yard. (I knew I couldn’t get it done all in one day by myself.)

Could I re-use the old concrete footing?

I wasn’t sure if I could -reuse the old concrete footings yet. First I had to get the old fence posts out.

How to remove a rotten fence post from concrete

Once the rotten post has snapped off, you can use a chisel and a long prybar to scrape out all the rotten wood remaining in the concrete footing (still in the ground). If it was a 4″x4″ post then the resulting hole in the concrete is very narrow and will require a skinny arm or long-handled post digger tool to reach down into the hole to ensure all the old, rotten wood has been scraped out.

In the photo below you can see the empty square hole where the old 4″x4″ fence post had been.

I hoped I could remove the rotten part of the fence posts from its concrete footing and still re-use the concrete footing. I thought I could just stick a new fence post down the old hole and it’d be good to go.

This would save me having to dig up the concrete, and I wouldn’t have to pour new concrete.

But the original posts rotted for a reason.

And when I inserted a new wooden post (4”x4”) into the old concrete footing and then gently rocked the post, the post swayed – it wasn’t solid – and actually the whole concrete footing moved underground back and forth. Not good.

At that point I knew I’d need to pull up the old concrete footings and pour new concrete.

Removing the old concrete footings:

I stuck a new post down into the old footings and used the new post as a lever. This allowed me to twist then pull the old footing right out of the ground. This went quickly.

When the old footings were out of the ground I could see that they were vastly undersized.  It looked like a long lollipop stick with a tiny concrete candy at the end.

And not only was the old footing really small, it was flat along the top: it wasn’t sloped to allow water to run away from the post. This likely played a large role in why the old fence posts rotted. Water would have seeped down between the wooden post and the concrete, and then pooled in there.

So if you plan on replacing a fence post into an existing cement footing, look at the existing footing and ensure that the concrete is sloped away from the hole and that there is ample gravel at the bottom of the hole to ensure drainage, and to prevent a new fence post from rotting again.

Remember to call your local utility companies before you dig to make sure you can safely dig in that area.

Digging the hole for the new concrete footing:

Pulling the old concrete footing out left a decent sized hole so I only had to dig down another foot or so.

With my 8-foot treated fence post I wanted a hole to be about 30-inches deep.

This is where there may be some controversy because some people think it should be 1/3 underground (which would be 32-inches underground). But I went with a 30-inch deep hole and 6-inches of gravel at the bottom, so my fence post was about 24-inches (or 2-feet) underground: leaving 6-feet of post above ground.

(Perhaps I should have gone with a deeper hole? But it seems pretty solid now that I’ve finished.)

Do you have an old wood fence but can’t afford to replace it right now?

If so, check out these 15 ways to make your old wood fence look better WITHOUT painting the whole thing.

Adding gravel to the bottom of the hole:

I put about 6-inches of gravel at the bottom of the hole for drainage. So if water did seep down against the wooden post it would drain through the gravel at the bottom and not pool against the post. (Water and wood don’t like to mingle together for long.)

I dug the hole, added the gravel to the bottom of the hole then tamped it down with the post.

Pouring the concrete to set the new fence post:

I bought 3 bags of Quikrete Post Haste concrete mix to fill the one fence post hole.

I thought I could dump the dry concrete mix into the hole and add water, but it turns out I was thinking of a different product. The instructions on the bag said I could mix it in a mixer or wheelbarrow.

Because the concrete is fast-setting (they say 20 minutes) and I was by myself, I wanted to brace the post prior to mixing the concrete.

To ensure the post was in line with the existing posts I put a taut string between the two posts on either side of the one I was replacing. I put the string at the bottom because I knew that since the other posts were wobbly too, their tops wouldn’t be aligned.

I set my post in the hole, had the front of it touching the string I’d just set up, then I built a brace to support the fence post so it was level front-to-back and left-to-right.

My wheelbarrow sucks and is falling apart so I had to mix the concrete in a plastic bucket.

I knew I had to work fast, so I had my water measured and ready to go beside my bucket. (One of the bowls I was using for water had measurements on the side so I could add the approximate 2 liters of water.)

I put on my P100 respirator (to avoid concrete dust) then I poured the dry concrete mix (one bag at a time) into the the plastic bucket, added the water, then quickly began mixing it with a little spade shovel.

I’d shovel or pour the concrete down into the hole to completely surround the fence post. Sometimes there was unmixed concrete at the bottom of the bucket so I’d add extra water and mix it around.

Because of working real fast and wearing the mask I was sure sweaty after mixing and pouring the 3 bags. But I got the three bags mixed and poured into the hole in about 7 minutes.

The top of the concrete was approximately 3-inches below ground level. I’m not sure why this is recommended, but I did it…

How to Stop fence posts rotting in Concrete – Slope the concrete away from the post

After putting the 3 bags worth of concrete into the hole and ensuring it nicely surrounded the post, I used a small garden shovel to slope the concrete away from the fence post. The idea it to make a little ramp so water flows away from the wooden post on all 4 sides.

Sloping the concrete away from the fence post and ensuring there is about 6-inches of gravel at the bottom of the hole should help stop the new fence posts from rotting in the concrete.

I let the concrete set all night. (I didn’t attach the existing fence panels back on to the post the same day. )

The one post that gave me some problems…

I replaced 3 rotted fence posts – one at a time. And it went really well. But then one of the posts gave me some problems.

One of the posts was in a precarious spot right next to the base of the large purple playhouse/shed in the backyard. If I dug out that footing I could potentially cause big damage to the playhouse.

So on this particular post I decided to try replacing the fence post in the existing concrete footing.

I dug and chiseled out all the rotted wood from the hole in the concrete. I planned on sticking a new post down this old hole. But then of course another issue came up: the new wood fence posts are thicker than the hole. The post wouldn’t fit down the hole.

So I had to get creative…and a little bit ugly.

I knew the old fence posts were only rotten at the bottom so I took an old post, flipped it upside down and stuck the “good” end down into the existing concrete footing. This meant a bit of the rotten part was now at the top. Not the most pretty thing ever, but it is strong and once I painted it, you can barely tell.

Painting the Posts Black

My plan was to solidy the foundation of the fence first (the posts) before worrying about cosmetics. But before I moved on to the fence rails and pickets I wanted to add some elegance to this simple fence.

I bought some semi-gloss black paint and I painted the posts black.

It took a few hours of rolling and brushing, but I think it turned out really well.

If you want to paint the posts on your existing fence you can take off the fence pickets on either side of the post and this allows you good access to get your roller in there and paint the post.

I still need to put some caps on top of the posts. If you’re in the States here is a link to Home Depot to check out the post caps they offer. I’m in Canada so here is a link to Rona for the black post caps that I’m going to buy.

I’ll highlight how I put up new rails and pickets in another article, but for now, here is a picture of the completed privacy fence. I think the black posts really make it look awesome.

Privacy Fence Ideas

If you want some more privacy fence ideas you should check out my article on 19 Privacy Fence Ideas (to stop snooping neighbors).

And if you have a chain link fence right now and you’re wondering what you can put on a chain link fence for more privacy, check out this article.

I built a “dog ear fence” so it isn’t suited to a fence topper, but if you want to put something on top of your fence, check out:

9 awesome Fence Toppers [to add height and make your fence look better]

Need a temporary fix before you can replace a rotten fence post? Check out my article on using the Fence Mender post support.

Plus, if you’re looking to beautify your yard or add curb appeal, check out:

• 10 Beautiful Front Walkway Ideas (front yard landscaping)
• 11 Low-maintenance, Easy-care Plants for your yard
• 7 Great-looking Lawn Alternatives (to save you time and money)
• 15 ways to make your old wood fence look better [today!]

Conclusion

I hope you’ve enjoyed this article on how i replaced rotten fence posts on my privacy fence.

I was nervous at first about having to pour concrete for new footings, but it turned out okay. It wasn’t as bad as I thought it’d be.

And if I can do it – all by myself- I bet you can too.

All in all, replacing fence posts wasn’t complex, but it did take some hard work. But the new footings and properly supported fence posts give me confidence that the new fence will last many years and continue to provide my tenant with a safe and secure privacy fence.