Tool to Remove Old Wooden Deck Posts From Water

Our backyard is surrounded by water and the previous owners of our house built a deck partly above the water. This deck is supported by posts that are standing in the water. One part of the deck was quite bad and partly rotten, so I decided to remove it. It was easy to remove the deck itself, but then I had to find a solution to remove the posts.

I did not want to cut them just beneath the water line, because children sometimes play on the water with small inflatable boats and the posts could damage their boats.

Our neighbors also removed part of their deck, but they hired a contractor with a large steel boat and a hydraulic machine to pull the posts out. I decided to try to build a tool that would help me remove the posts by myself. It worked surprisingly well, so I decided to share what I did.

In this Instructable I will first describe how my tool works and then I will give more details on how you can build something similar. I can imagine that a step is not fully clear immediately, but if you continue reading the next steps, I think the additional photos will make things clear.

The design was a result of a phone call between me and one of my friends. I told him that I was trying to figure out a way how I could remove some posts out of the water and we were brainstorming a bit.

Pulling would only be possible if there was some solid surface to push against. That solid surface had to be the bed, which was about 70 cm (28") under water. So I could use a steel pipe that would fit around the post and at the bottom of the steel pipe there should be some kind of support plate for the pipe to stand on and to prevent it from sinking in the mud around the post.

Then I had to be able to pull on the post, so I would drill a hole through the post and place a nut and bolt through that hole.

Next, I had to fabricate some kind of hook, to be able to hook behind the bolt.

Then some threaded rod to be able to use a large pulling force.

Probably it is already getting confusing, so let's first look at how the tool works.

Remark: I did not take many detailed photos when I was actually using the tool over water, so these photos show how the tool works without the risk of dropping my camera in the water :-)

Remove any horizontal beams connected to the posts, so you have just the wooden post itself remaining in the water.

Drill a hole through the post and place a bolt and nut through that hole. Make sure you use a bolt size that is thick enough so it will not bend and short enough so it will fit through your pipe.

Check that the hook from the second photo will fit properly over the bolt. You should not tighten the nut and leave some slack, so the hook goes between the nut and the post and between the bolt head and the post at the other side.

Place the pipe of the tool over the post and let it sink below the water level.

When you plan to build a tool like this, make sure you use a pipe that is large enough to fit over your post (including hook) and long enough so the top of the pipe will be above the water level.

Connect the hook at the bottom side of the threaded rod and slide the triangular piece over the top end of the threaded rod. Then add a washer and nut on top of the triangular piece.

Place the hook so it hooks around the bolt that is in the post and hang the triangular piece in one of the angle iron pieces.

The first photo shows the hook hanging from the threaded rod and hooked around the bolt. On this photo the pipe is not present, so you can better see the hooking system, but when you use the tool, the pipe must already be placed over the post.

The second photo shows the triangular piece.

The third photo shows the triangular piece that is now hanging in one of the angle iron pieces. The black arrow on that photo shows the washer and nut that you added last.

Now get a spanner and keep tightening the nut (the one indicated by the black arrow). The nut cannot go down as the triangular piece is locked in place, so the result is that the threaded rod has to travel upwards. The post will resist that movement, so the tool will be forced further down into the mud at first. Just continue tightening the nut and then the post will start to come up.

Here you see me using the tool. I added a string to the spanner so I would not have to dive for it in case I dropped it into the water.

Since the spanner can only turn the nut about 120 degrees, it takes several minutes to pull the post up about 30 cm (one foot).

When the hook reaches the triangular piece, I released the tension from the threaded rod and put the triangular piece higher.

The vertical travel is limited by the position of the top of the tool. So I removed the tool from the post (then you are happy that you did not make the tool too heavy) and I used a saw to cut the post shorter. I then drilled a new hole and repeated the process.

It is much easier if you can use a ring spanner which can make full circles in tightening the nut. For that reason I have a horizontal piece of steel at the top of the tool with a washer to center the threaded rod in the hole.

I had a threaded rod that was only about 60 cm (2 feet) long, so I could not directly start with the threaded rod all the way through the top hole. It is definitely worth getting a 100 cm (3 feet) long threaded rod for your tool, but with a shorter one like I had, it also works, only I had to use the triangular piece first.

With a longer threaded rod, you do not need the triangular piece.

On this photo you can see two of the posts that I removed from the water. One was 5 meters (16 feet) and the other one 3,5 meters (11 feet). Fortunately the posts came loose after lifting them about 1 meter (3-4 feet) with the tool, so for the last part I could just pull them out of the water.

(We live in an area where the soil does not have much strength, so long posts are needed even for simple structures like a deck.)

I made the tool from left over pieces of carbon steel. I got them from a company that builds industrial machines and they have a waste bin for cut off pieces of steel that will be recycled. Those cut off pieces have only little value to them and I asked if I could use some of those pieces and I was allowed to take them for free.

The wall thickness of the steel I used, varied between 3 and 6 mm (1/8" - 1/4"). If you have a choice, pick some steel that is strong enough to withstand the forces involved in pulling the posts, but not too heavy so you can still carry the tool and place it over the posts.

The base of the tool is a metal plate with a hole in the middle for the post. Since I only had small scrap pieces of metal, I used 4 smaller pieces and welded them together. That made it also easy to cut the hole in the middle, so I cut the hole before welding.

When the base place was ready, I placed the pipe on top of it and welded it to the plate.

Dimensions depend on your specific situation, so keep in mind that the post and hook have to fit through the pipe and the post must also fit through the hole in the base plate.

Add two vertical beams and weld them to the pipe. Cut small pieces from an angle bar and weld them with the point facing downwards to the inside of the beams so they can support the triangular piece later. (If you use a long threaded rod, you can skip the angle bar and triangular pieces.)

Make a horizontal piece to connect both vertical beams and to be able to use the tool more efficient from the top side with a ring spanner.

The threaded rod needs to be strong so I used a M16 threaded rod. That is about 5/8".

Think how you will make the hole on top as it requires a larger drill bit than commonly fits in a drilling machine. I could borrow a special drill bit, but you can also cut a larger hole with an angle grinder. I welded a washer on top as that had the correct size to center the threaded rod.

The two 45 degree cross braces are there for some extra strength.

The hook consists of a small piece of a U-beam, two strips with a slot cut into them to be able to catch the bolt.

On top I welded a nut where the threaded rod will be connected. The washer is there because the end of the threaded rod might be rounded off a bit so the thread does not come completely to the end. This way I make sure all threads of the nut help to carry the load.

The triangular piece is only needed if your threaded rod is not long enough to reach the top of the tool.

It consists of an angle bar with a strip welded into it. I cut a hole for the threaded rod with an angle grinder and welded two washers in place to center the threaded rod.

I used the tool and was happy with it as it did the job.

If you also built it, please let me know your experiences.