Page 1 of 2 12 LastLast
Results 1 to 15 of 16

Thread: best way to level concrete floor

  1. #1
    Join Date
    Feb 2017
    Location
    Rochester, NY
    Posts
    127

    best way to level concrete floor

    The concrete floor sank, probably decades ago from poor prep. Has since been stable. Was poured 30+ years ago

    There is no heaving as it has rebar. It is not painted and the surface is in great condition - just sunk down ~3" over a 15 ft span.

    I have seen videos and read about the self-leveling material you float onto the floor and feather in, but I have also heard it is very 'soft' compared to concrete.

    Anyone here have any experience with this?

    thanks,
    DW
    DW

  2. #2
    I've used self-leveling (which is a misnomer) a fair bit. It is pretty strong except where feathered to a thin edge. I don't believe you want to use it to level a 3" difference. For one thing it would be *really* expensive. Second, you would need a ton of helpers to mix enough compound and distribute it fast enough to avoid cold joints (it starts to set up really fast).

  3. #3
    Depending how much money you want to spend, one way to do it is to hire a company that does "slab-jacking." This procedure involves drilling a series of holes at the low side of the slab, inserting nozzles and pumping concrete under high pressure to raise the slab back to the original level. It works well, but is not cheap.

  4. #4
    Join Date
    Feb 2017
    Location
    Rochester, NY
    Posts
    127
    Brian, I have seen the mud jacking/slab jacking companies. Problem is, my area is finished with the bottom plate of walls tap-conned to the floor. If it were jacked, it would push the ceiling up.

    Paul, would you suggest using a cheaper material to do most of the filling, or even something like tamped crusher run first and then level over this? If not, any other alternaitves?

    thank you,
    DW
    DW

  5. #5
    Join Date
    Jul 2005
    Location
    Eastern Iowa
    Posts
    437
    Quote Originally Posted by dustin wassner View Post
    Brian, I have seen the mud jacking/slab jacking companies. Problem is, my area is finished with the bottom plate of walls tap-conned to the floor. If it were jacked, it would push the ceiling up.
    ......
    DW
    So, if you added material to level the floor, the bottom plate and stud bottoms of the lowest wall would be three inches below the added concrete, and the side walls would be incrementally below the concrete?

    To me, it sounds like a do over on the finished walls...

    edit: or... time to add a hardwood floor.
    Remediate any moisture problems -sounds like none if it is finished space.
    Add sleepers properly shimmed to level the area,
    Apply flooring
    Last edited by Charlie Velasquez; 07-20-2019 at 8:56 AM.
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

  6. #6
    I tend to agree with Charlie's second suggestion. Install tapered sleepers (pressure treated), cover with plywood, and add flooring. If there are doorways in the low area that will take some rework. A line laser set on the floor speeds up the process of measuring for the sleepers.

    You could pour a new slab on top of the existing but not a good idea to bury all the wall bottom plates. And there's always a chance the extra weight would cause the existing slab to settle some more.

    What puzzles me a bit is why the original slab wasn't supported along the edges by the footings?????

  7. #7
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    48,988
    Yea, I like the overlaying with wood idea, myself. A 3" dip is pretty extensive and not something that's going to be accommodated well with any pourable leveling media. Custom fitted sleepers and a sheet goods floor does the deed nicely, can add some insulation benefit if that's important to you being up north and all that, and be a lot more comfortable on your feet long-term. You'd only be "losing" about 2" max of headroom, give or take, too.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
    Quote Originally Posted by dustin wassner View Post
    Brian, I have seen the mud jacking/slab jacking companies. Problem is, my area is finished with the bottom plate of walls tap-conned to the floor. If it were jacked, it would push the ceiling up.
    I'm sorry but I'm having trouble understanding what you mean? If the walls are fastened to the slab, and they lift the slab, doesn't that lift the entire building? I mean, why would the height of the ceiling change in relation to the floor? (Other than to move everything back closer to plumb?)

    Fred
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  9. #9
    Join Date
    Aug 2015
    Location
    N. Texas
    Posts
    1,304
    Quote Originally Posted by dustin wassner View Post
    Brian, I have seen the mud jacking/slab jacking companies. Problem is, my area is finished with the bottom plate of walls tap-conned to the floor. If it were jacked, it would push the ceiling up.

    Paul, would you suggest using a cheaper material to do most of the filling, or even something like tamped crusher run first and then level over this? If not, any other alternaitves?

    thank you,
    DW
    Never done this, watched it done, or lived with the aftermath - - so take this for what it's worth.

    I have heard of 'folks' using 2 methods for remediation of said subsidence (...how's that for $45 worth of words?):
    1. Pure Portland cement with lots of water.
    2. Tile underlayment - goes under several brand names, but basically is just fly-ash (burned coal with proper lime content).


    Both are a top-down fix, unlike jacking. Neither is a 'structural' fix; the floor won't be any stronger or more stable than it is now, as I understand it. Both flow out like water (self-leveling). Both have lousy tensile strength, but decent compression strength. If your existing floor twitches, both of the above will crack - immediately, according to my 'folks'. I know in the 2 cases I can remember, they covered the relatively small patches with a finished floor (tile/hardwood/vinyl/etc??), just can't provide that detail.

    Dimly recall someone suggesting/using a shallow (i.e. 1/2" - 3/4" deep) saw-cut at the otherwise feathered edges to improve bonding and limit spalling. IF you can accurately predict where these edges will fall..?? Concrete or tile installer might give you some clarity here...?

    IMHO, both were a last ditch effort to salvage a bad situation. I can't recommend either, but hope the info (rumor & innuendo?) is some help.

    Good luck and I do hope you find a good path forward.
    Molann an obair an saor.

  10. #10
    Join Date
    Jan 2009
    Location
    N.E, Ohio
    Posts
    2,722
    Quote Originally Posted by Frederick Skelly View Post
    I'm sorry but I'm having trouble understanding what you mean? If the walls are fastened to the slab, and they lift the slab, doesn't that lift the entire building? I mean, why would the height of the ceiling change in relation to the floor? (Other than to move everything back closer to plumb?)

    Fred
    Yes the whole building would be lifted. The question is ---- What is above this space?? Is there a floor/ room above? If so is one end 3" lower than the other? Raising the walls attached to the existing floor would likely cause structural issues.
    George

    Making sawdust regularly, occasionally a project is completed.

  11. #11
    Thanks George. That helped!
    Fred
    "All that is necessary for the triumph of evil is that good men do nothing."
    - Sir Edmund Burke

  12. #12
    Join Date
    May 2008
    Location
    Central Florida
    Posts
    30
    In my profession, I have fixed/leveled out many, many floors (some much worse than yours). Dry pack, (3 parts coarse sand/1 part portland) would be the best for your job. Build the level screeds one day (a laser level comes in handy) and do the fill the next day. Use a bonding agent (Lanco works really good) for a strong, permanent bond.

    You can feather edge the dry pack as thin as 1/8”-1/4” if you use a good bonding agent. For a nice, durable surface, skim over with a high quality thin-set with portland cement mixed in it.


  13. #13
    Join Date
    Jan 2007
    Location
    Davis, CA
    Posts
    260
    How about some pictures. 3 over 15 feet is a lot. If the sill plate is bolted to this the whole structure must be tilted. I assume this is a separate structure. I would be tempted to cut the tapcons and raise and straighten the structure and pour a new floor over old or preferably bust out the old floor.

  14. #14
    Join Date
    Mar 2019
    Location
    Los Angeles, California
    Posts
    46
    3" is a lot. I'll give you my two options.

    First, the best and probably easiest way is to figure out where the floor dips to the level of 3/4 to 1" and bust out the lower areas. It won't be hard, it will come right out. Re-pour. Use Self Leveling Compound to feather in from 0 to 3/4" It is softer than concrete and I think I would want to cover the floor with something, cheap tile, vinyl, something. SLC will get chewed up pretty easy. It is not engineered to be a finished surface, merely a substrate.

    Second, pour the SLC in layers, about a half inch. You can use lathe or chicken wire on the lower third of the pour. The stuff is not cheap and is not engineered to be a finished surface, it is merely a substrate, so cover it with something.

  15. #15
    Join Date
    Jan 2007
    Location
    Davis, CA
    Posts
    260
    Pictures would really help of an outside view of the whole structure and the connection of the structure to the sill plate. I am still confused as to whether the structure is tilted or just the floor. It it is just the floor, bust it out and re-pour.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •