I am building a floor and the first step is attaching ledger boards to existing studs around the perimeter of the room. The joists are JITs that will then be put in hangers attached to the ledger boards. . The problem is that it is essential that the ledger boards be perfectly flat and parallel with each other, otherwise the joists will not be level. The dimensions of the room are 23' x 17'.

How can I ensure that the tops of the ledger boards are flat and level with each other?

2 Answers 2


Use a level. There are many types.

  • A simple string and a bubble level. Use a 4-6' level at the center of the span (to account for sag).
  • A bubble level on a common joist. Obviously this is heavier, but with a helper it can be done. Set your first ledger and install a hanger. Place the common joist and lay a level on the other end, extending to the wall.
  • A laser level. Mount it in a convenient location and measure up from its beam.
  • A water level. Fill a length of clear tubing with water. Lift both ends until the water line is at the joist height.

I'd use a line level to snap a chalk line, this way very quickly you have a mark on every stud.

line level

Next double check the marks with another tool, preferably a water level. A water level is extremely accurate - probably the most accurate thing you could use - cheap, and pretty much foolproof.

water level

  • Be aware that short levels have a larger margin of error. I'd reverse it after making the mark and average the two marks. (Actually, I do that with any bubble level.)
    – isherwood
    Jan 21, 2019 at 18:39

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