I recently had my back door removed and replaced with a sliding patio door. When framing the new opening, some of the framing was rotten and replaced. Due to the house being 118 years old, things aren't always perfectly square and level. The new subfloor is a bit sloping right around the door. The framers installing the door said this would be no big deal for the flooring guys, and that they are used to this sort of thing.

Turns out, 2 flooring guys say they can't deal with this. The slope is about 1" over 12", then the 3/4 plywood the door is on.

What kind of options could I employ to level this area out? While I could fabricate a bunch of large shims to exactly match the profile, it would be a time-consuming hassle. Would something like a self-leveling concrete or epoxy resin type material work in a situation such as this, if the area was adequately sealed from leaking? What other options might there be?

Here's an image of the overall situation. The subfloor on the right is the 'original', while the vertically oriented plywood is the new subfloor installed by the framers for the door.

Overall Situation

View of the overall deflection. The old subfloor is reasonably level, and this picture was taken with someone stepping on the level placed in the gap in the flooring. The difference between the ideal and the bottom is about 1".

Deflection overview

Another view Detail

  • Floors can't move up, things can only go down. If the section of subfloor that the level is resting on is level, the door isn't where it's supposed to be (too low). It looks like there's been some foundation settlement. What is the section of subfloor next to the door resting on? It looks like there may be something strange going on with the floor joists there. Just filling the gap isn't a solution for the apparent structural issues. Rotted framing probably wasn't the only, or most serious problem. Discovering it could be fortuitous. (cont'd)
    – fixer1234
    Aug 22, 2020 at 6:40
  • You should have an engineer look at it. It might need something like helical piers to stabilize the foundation and get everything level and where it should be. If the joists are actually OK, people may have added multiple layers of subfloor over the years, and you could be missing a layer near the door (the sunken piece may be resting on the edge of a layer poking out from under the next section).
    – fixer1234
    Aug 22, 2020 at 6:40
  • 1
    @fixer1234: the framing is fine structurally, apart from the slanting. The house was resided and resheathed so we had complete visibility into what was going on. And yes, the reason for this is there has been some settling, it's a 118 year old house. Had I known the floorers would have balked at the job, the framing could have dealt with it but it wasn't so here I am. Aug 22, 2020 at 15:07
  • @whatsisname what'd you end up doing? I have the same exact problem!
    – Steven
    Dec 19, 2023 at 9:36
  • @Steven a different floor company came with a portable table saw and cut a boatload of shims of different sizes. They also tore out the rest of the floor from the new door to the opposite wall, 3-4 feet or or, plus about a foot on each side. With the shims and new boards they could carefully bend them as they installed them and blend it all together. Then finished by sanding and refinishing the entire floor. Turned out well. Jan 10 at 7:48

1 Answer 1


This looks like a job for self leveling compound. I would probably do it in 2 pours it looks a bit thick for a single pour. What kind of flooring are you installing? It looks like there will be enough height at the door for just about any kind of flooring Once leveled.

Folks that haven’t worked on old homes don’t realize true dimensional lumber was once used. Plywood is thinner the 2x4” are thinner today and may be the cause of the height issue.

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