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I have about a 1" height difference on my concrete basement floor. My understanding this was for drainage in case of flooding. I have a wall in the way of where anything could potentially drain in the future so keeping the slope for drainage no longer makes sense. The 1" drop is over about 12' and there are a variety of reasons I would like to level the floor. I will have bypass doors for closets and there will be a funny looking gap under one side of the doorway if the floor is not level. The room will be an office and I don't want to sit at an angle or roll downhill on my chair. Desks and things would also be out of level. Baseboard trim would be slightly more difficult to install on a slope.

I do not want to raise the floor more than necessary because I want the doorway (on the highest corner of the room) to flow smoothly into the rest of the basement if possible. I plan to use Luxury Vinyl Tile/Plank on the floor.

I have a few ideas for how to level the floor without raising the height more than needed.

  1. Pour self leveling cement. This would probably be the easiest and most straightforward but it would also be over $800 to level a 12'x16' area with a 1" slope over 12'
  2. Sleepers with plywood subfloor for lowest area + self leveling cement on higher area. This would save a lot of money by filling the bulk of the area using sleepers and plywood and then for the smallest 4' or so of the slope use a small amount of self leveling cement that butts up to the plywood and sleepers
  3. Cement board backfill for lowest area + self leveling cement on higher area. I would stack several sheets of cement board to back fill the areas I can then fill remaining space with self leveling cement (either going up to the cement board or overtop it and encasing it)

Are there any major problems with any of these ideas? #2 would be cheapest I think but also a bit more work and potentially more problematic for a variety of reasons. I'm leaning towards #3 but I'm wondering if there are any problems with that plan. I would just use thinset to attach it to the existing concrete floor, stair step the sheets of cement board, and then use self leveling cement over the entire room, including the cement board for a smooth finish.

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    No one can give you a proper answer without specific drawing, schematics and pictures. #2 and #3 just seem ridiculous and I specialize in basement renos. Also you mention a wall - guessing wood framing? If so trust me water will still drain under it. It sounds from your info that the floor slopes to some outer drain system... You have a slope to it and tons of water gets in you can have it cleaned up in 30 mins and probably not have to pull the vinyl up. If there is no slope you are pulling vinyl up every single time or you will have moldfest.
    – DMoore
    Jun 24, 2021 at 3:57

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start with mortar or fine concrete screed where there's a lot to fill and then use self leveling cement to finish. where the fill needed is more than 1/4" self-levening cement is best used second.

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    And pouring concrete will be half the price of the sheets, plus save on thinset, and save headache trying to squeeze the sheets flat with thinset in between.
    – P2000
    Jun 24, 2021 at 5:57
  • Screed is also known as deck mud, right? Jun 24, 2021 at 12:46

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