Before we bought our extreme fixer upper, we watched a lot of Holmes on Homes. In addition to an irrational fear of hiring contractors, the show also instilled the importance of building level, plumb, and true. When you’re renovating an old house that’s something of an uphill battle, and at times it’s downright impossible. However, we’re planning on in-floor radiant heat, which uses plywood and aluminum panels that lie on top of the subfloor and has channels for PEX tubing. The subfloor needed to be level and flat, and the existing plank floor was not going to cut it.

Wet wall subfloor

The first new subfloor was done when I reframed the wet wall back in September. At the time I decided that “level” was where the joists rested on the steel beam at the center of the house, since I knew the beam was level. The joists sloped slightly higher toward the South wall, so I used a planer to shave them down to be level and put the new subfloor down. I call this planing method of leveling “Method One”.

Shimming over subfloor

When I started work on the back section of subfloor, I realized that the wet wall was the exception rather than the rule when it came to joist height at the South wall. Most joists were ¾” higher at the outside wall than the beam, making Method One a bad option. Not only would planing that much off be a time consuming pain, I didn’t like removing that much wood from the joists. I decided instead to establish a new level, on top of the small section of subfloor I’d already done. Instead of planing down, I cut and glued down long shims that tapered from nothing to ¾” (depending on the particular joist) over the course of ten feet. This is “Method Two”. It is also a pain in the ass, but slightly less so. There were a few variations of this while we tried to work out the best way to do it.

Jacking up joists

With the back section leveled, but time consumingly so, I wanted to find a faster way to do it. Since the ¾” slope was fairly consistent, I next tried jacking up each joist at the beam and/or the outside wall and putting a shim underneath it, using my trusty hydraulic jack. This is “Method Three” and so far the most straightforward, if still time consuming. In some cases this was all I needed to do, while in others there was still a bow in the center of the spans that I fixed with a long shim, ala Method Two.

I did consider some other methods, such as sistering another joist to the first one. Some people have even used just a 2×4 rather than a full height piece. I didn’t do that partly because I didn’t want to rip out and replace all of the cross bracing between the joists, plus I don’t like the idea of the weight being carried off center of the joist. I want the floor to be as quiet as possible, which is why all the shims and subfloor are being glued down in addition to screws.

Shimming under the joist

I still have a ways to go before the subfloor is done. I’m doing the leveling and the subfloor installation concurrently because we need a way to walk through the first floor, plus a place to put all of our tools. I’ll be working on it in the evening this week as well as this coming weekend. I’m hopeful I can finish by Sunday, but we’ll see.