I need to lay some temporary(about a year) flooring in a room. The house has a crawl space under it and the floor droops slightly, about 1/2 an inch in the center.

It was suggested to me to that I should put some shims where it is low, lay the thinnest piece of plywood I could find across the entire room, and then install which ever flooring is decided upon(will either be carpet or laminate wood). The room is roughly 9x10 feet.

Is there a better way to level the floor? Would shims be suitable or should the center of the room be built up with something else? Is this just a horrible idea all around?

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  • 2
    Unless it's a VERY small room, the best thing to do with a 1/2" dip for a temporary floor job is - ignore it.
    – Ecnerwal
    Dec 5, 2015 at 16:02
  • @Ecnerwal the room is roughly 9x10. Would this be considered small enough to ignore the dip? Dec 5, 2015 at 16:04
  • 1
    Is the "looks to be an old trapdoor" the "low spot" and is it a precipitous 1/2" drop all around the edge of that? If so, you might need to fix it. If it's just 1/2" lower in the center, that's 1/2" in 4.5 feet one way, 5 feet the other, for less than 1/8" per foot in any direction - which you don't need to fuss about. In a 2x2 closet that would be a large dip - in a 9x10 room, it's barely noticeable. Personally, unless there's something going on not in the picture, I'd just leave that floor alone or do a better job with the ex-trap-door looking part.
    – Ecnerwal
    Dec 5, 2015 at 16:10

2 Answers 2


Thin plywood will only flex and make noise. Anything on top of shims must be able to carry the load of furniture and foot traffic just as a standard subfloor must.

If your floor slopes gently just half an inch, there's probably no reason to do all that work. Most flooring will accommodate that. Lay your temporary flooring on what you have. If you do need a better substrate for the particular type of flooring, lay some inexpensive 1/4" OSB or mahogany plywood to provide a smoother surface.


Shims are one way to go; they're fast and covered with sheet material will level the floor. The problem is unless the edges of the plywood are sanded or feathered down, they will eventually 'telegraph' through the temporary flooring (if the new flooring is carpeting) or cause alignment problems (if covered with wood planks). Consider using a floor leveler. This is a powdered substance that is mixed to a slurry type consistency. It is poured onto the floor's low spot and then floated with a straight edge until it fills the depression. The edges can then be feathered to a smooth transition to the surrounding floor. Once the slurry sets up it will accommodate any new flooring. It will stain wood so if you are deciding to use the original strip floor it will need to be re-finished.

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