I'm in the planning stages of a basement refinishing project. The basement has a concrete slab that is in decent shape but needs a few things:

  • Some sizable (6"x6"x1/2") protrusions need to be ground down
  • Some similarly sized areas need to be filled in
  • It is otherwise fairly flat, but definitely not level (say 1/4" slopes over 6').

I'm going to basically be partitioning the area into two rooms (a workshop and a laundry/bonus room). My question is, do I tackle the entire floor first by doing the grinding and leveling across the entire area, or do only the messy major repair first (grind/fill in) and then do the leveling after framing in each of the two areas? I plan to put down vinyl planks so from what I understand it's typically cement/underlayment/vinyl planks. I was planning to use a self-leveling product for the first step.

In other words, do I not try to get the whole basement level across its entire dimension, but rather make only the two rooms level within themselves, to try to make it a smaller job and not require so much of the self-leveling product.

Also, if anyone has an advice on how important it is to get it level vs. simply flat and relatively level, that would be good to know.

Any help is appreciated!

Thanks, Jared

  • I really think this is an opinion type question. Since you only care room to room it may be easier to do it in small chunks. But getting all the grinding done first would be my priority so the cleanup mess is not as bad.
    – Ed Beal
    Mar 15 '21 at 15:24
  • You indicate that there is a pretty slight slope, but remember that drainage plumbing is 1/4" over 4', so your 1/4" in 6' isn't that level (you are correct, though, you want flat, not level for your flooring). If you decide to level each room individually, think about it now or you might end up with a noticeable step between rooms that would be more of a hassle to deal with than leveling the entire floor would be.
    – FreeMan
    Mar 15 '21 at 15:30
  • Thanks. I was wondering about the transition between the rooms if I do them separately. Some sort of threshold would be fine by me and seems like less work than trying to get the entire area level, but I'll have to think about that some more.
    – Jared M
    Mar 15 '21 at 15:32
  • @Jared M The 1/4" over 12" is the typical slope of basement slab, the purpose is to facilitate water draining, shall the basement be flooded I suggest to identify the floor drain, make sure water path is not blocked, then perform local leveling as desrired.
    – r13
    Mar 15 '21 at 16:18

I'd definitely want to do all the grinding first. You'll probably have to rent the grinder and why do it twice. Also, you'll get grinding dust everywhere unless you really wet it down.... messy. When you frame the rooms, you don't want protrusions.

The filling in could be done as you go along because the rooms are divided. Being level isn't as important as being flat. I've been in many residential construction sites and have seen very few totally level foundations.


Jack is right. You want to grind down everything first because it is a freaking mess and just get it out of the way with nothing else going on there - or as little as possible.

The leveling... ummmm no. Basements are not supposed to be level. 90%+ of basements will slope to a floor drain. Your floor drain I am guessing will be in your laundry area. You don't level that or anything else - unless there was some buckling or wild deviance from the original pour.

You do not want water leveling off on your entire floor. You want water redirecting to a "low spot" so that you can manage it and dry off the rest. This is just good building science. If I ever walked into a basement, finished or not, and felt like the floor was "level" - that to me is a huge huge red flag.

As for floor covering - you will not be able to cover the ~6' near the drain. The rest of your basement can be covered based on the properties of the slope. If it is flat and pretty continuous you can go with laminate (I only do pure rubber in basements), you can go with carpet or tile. If it is really choppy you may only get by with carpet in the finished areas. If it is somewhere in between you are looking at carpet or tile.

  • Thanks, DMoore. That's a great point that basements should not be level. So maybe I have less work to do after all. That said, there's definitely no drain at some central low point. The floor of the basement is below the drain to the street, so now we would be talking about a pump and all that as well. I'm pretty set on the vinyl planks with an underlayment so I'd be curious to know how bad you think it would be to take my chances on that once I've repaired the floor. Thanks again.
    – Jared M
    Mar 15 '21 at 18:35
  • I guess for context I should I add that I live the in Northeast and the house is 120 years old. While I know basement flooding is a definite problem, we've lived in this house for 7 years and the basement has stayed dry all that time. Even during heavy rains and large volumes of melting snow up against the house. The surrounding grade is favorable (everything slopes away from the house), so I imagine that helps.
    – Jared M
    Mar 15 '21 at 18:42
  • Well you need to work on the same basic premise. Instead of going to a floor drain you need a sump pump. Dig and install will cost you a day and ~$500. You cannot just do all of this work on your basement and have no plan for water. I would start by dumping out buckets of water and see where it floors (you will have to do this to clean up the grinding). I would pick the lowest place and install sump pit. If there are many low places you need to plan this out.
    – DMoore
    Mar 15 '21 at 18:59

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