Fixing a Sagging Floor

I finished up the basement support beam last night. We no longer have a floor in the log cabin that sags or bounces. When you walk up there, it’s as firm as a fiddle. And it only cost me around $15.

I already showed you the first half of this project. If you haven’t read it yet, you can find it right here. If you have, then just keep on reading.

Since I had already set up the support beam, all I had to do was get some lumber, set up some cement blocks, do some measuring and cutting and BAM – done. So that’s what I did. And I have pictures to prove it. I’ll go through them below.

The first thing I like to do when I’m fixing a sagging floor is to see how bad it really is. In this case, I knew the situation wasn’t terrible. Probably a half inch at most. What we really noticed and what the main problem was was the bounce. Laura would stand on one part of the floor and I would jump on another. Let’s just say she would feel it. So that was my main concern. The floor has a 12 foot span across, so it really needed some sort of a support below.

It’s very simple to measure the sag of a floor with a laser level. I like to set it up with a regular thumb tack and then let the laser do the rest. I start the laser on the lower most part of the floor joist and run it along the beam to the lowest part of the other side. If you see a red line somewhere in the middle, you have a joist that sags. And if you measure how far the line is up on the joist, you’ll know how much does.

Next, I measured where I was going to put the posts. Initially, I was going to screw together two 2x4s each to create two 4x4s. That would give me two posts. I changed my mind when I realized that I didn’t need that much strength down there. The posts are only holding up less than 100 pounds, so I decided to keep them as 2x4s and put in three. Three is better than two.

After I measured where I was going to put the posts (4 feet apart), I hung a weighted string to cement blocks below. I wanted the cement blocks directly centered below the posts. This would make things very simple when it was time to install each post.

This picture is out of order. I simply wanted to show you the floor jack and board I used to jack up the floor. Later on and once the cement blocks were set up, I put the jack on the cement floor and worked from there. Here, I was looking to see how heavy the floor was going to be.

After I jacked up each section where each post would go, I placed the 2×4 on the cement blocks. I marked where to cut them, cut them and pushed them into place. I made sure to keep them level and then let the jack down. If I did a good job measuring, the floor wouldn’t lower. It didn’t.

Since there was very little weight at the end of the support beam, I used a piece of 2×4 to hold that section up. It was dipping down slightly, so this was necessary.

A perfect job. Now, the floor doesn’t bounce at all and is totally level. The picture above looks distorted because of my wide angle lens. Don’t let that fool you – things are straight.