How to Raise and Replace a Deck Post

Question on replacing a 4×4 Deck Post with a Heftier 6×6 Deck Post

By Mark J. Donovan

Question: I have a deck that was built several years ago and I have had a concern with the supporting deck posts that were used. The supporting deck posts, which are approximately eight feet tall, are 4”x 4” pressure treated posts. I have been concerned that they are inadequate for the weight that they are holding up and I want to replace them with 6”x6” pressure treated deck posts. The question I have is how can I raise and replace the deck posts?

Answer: There are a couple of ways you can raise and replace the deck posts. One way is to use a jack designed for home construction projects. In addition, you will need several 2”x4”s.

Take two of the 2”x4”s and nail them together such that the end side of one butts up against the flat side of the other to form a T. Repeat the process with another pair of 2x4s.

Next, temporarily install a section of 2”x4” across 3 of the deck floor joists near the area where the post to be replaced resides. Use a couple of screws to hold it in place.

Next place a section, approximately 3-4 feet in length, of either a 2”x 6” or 2”x 8” on the ground. Make sure the section of material is level and on solid footing. The jack will rest on this surface.

Next place one of the T-formed 2”x4” pieces up underneath the 2”x4” that is nailed to the floor joists. Preferably locate the top of the T-formed 2”x4” under the middle floor joist area that the attached 2×4 section runs across. Toe-nail in the top of the T-formed 2”x4” to the section of 2”x4” connected to the floor joists. This will prevent the T-formed section from slipping out when it is under load.

Now place the jack underneath the T-formed 2”x4”. The jack should be resting on the 2”x6”/2”x8”.

Note: You may need another small block of flat surface material to sit between the bottom of the T-formed 2”x4”s and the jack itself. You may also need to trim the T-formed 2”x4” to length to allow the jack to be positioned under it.

Next, make sure the deck post is free to lift from the concrete base that it sits on.

Turn the jack-screw to raise the deck up. You will only need to raise the deck up about a half inch to have clearance to remove and replace the old deck post.

Once you have the deck raised, place the other 2”x4” T-formed-piece between the 2”x4”-section attached to the floor joists and the 2”x6”/2”x8” that is lying on the ground. You will probably need to cut this to length. The purpose of this T-formed piece is to add some safety to the project.

With the post off the ground you can simply remove it from the deck and replace it with the new 6”x6” post.

An alternative to a Jack

If you do not have access to a jack, you can alternatively use a couple of 2x4s to create an inverted V to lift the deck.

In this situation, toe nail two 2”x4”s to the section of 2”x4” that is attached to the deck joists. The 2”x4”s should rest on the 2”x6”/2”x8” piece on the ground, however they must be of length that they form an inverted V.

Using a sledge hammer, wedge the two 2”x4”s together to form a tighter V. This will raise the deck. Once the deck is raised, attach a couple of small blocks of wood (using 16-penny nails) to the 2”x6”/2”x8” on the ground so that they butt up against the outside edges of the two vertical 2”x4”s. This will prevent them from slipping.

Finally, place a 2”x4” T-formed-piece between the 2”x4”-section attached to the floor joists and the 2×6/2×8 that is lying on the ground for added safety.

For help on building a deck, see HomeAdditionPlus.com’s Deck Installation Bid Sheet. The Deck Installation Bid Sheet will teach your how to hire the right deck contractor, and help to ensure that your deck project is completed on time and budget.

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