Leveling a wooden floor — how measure it and how to shim it?
markmiller2
| Posted in General Questions on
100 year old house, 12×12 upstairs room with T&G plank subfloor. I want to level and strenghen. Room sags toward the center.
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Replies
Mark,
In my opinion, the best approach is to remove the subfloor. (In some cases the subfloor boards can later be re-installed.) Then sister new, level joists to the sides of the existing sagging joists.
That had been my plan but I'm worried that the brittle subfloor and rock hard 2x4 joists will wind up cracking the plaster of my dining room ceiling and it's not worth the risk, so I'm looking for the second best approach. Thanks
You could level w/o removing subfloor, but hard to see how you'd strengthen.
Mark,
I forgot to answer your question about how to measure your out-of-level floor. There are many ways to do it, but you can always start by using a 4-foot level.
Since your room is 12' x 12', it would also be useful to have a straight 2x4 that is 11'10" long. Using the long 2x4 and the 4-foot level, you should be able to find the high spots and the low spots on your floor.
Mark,
You wrote, "I'm worried that the brittle subfloor and rock hard 2x4 joists will wind up cracking the plaster of my dining room ceiling."
First of all, if you are undertaking a major renovation project that involves leveling a sloping floor, you need to be prepared to patch plaster cracks. Repairing cracked ceilings isn't that hard.
Second, there are ways to attach a new joist to an old, rock-hard joist. If you really can't manage to attach the new joists with nails, you can predrill holes for your nails, or predrill for screws or bolts. Don't forget to use construction adhesive, too.
The floor is framed with 2x4 joists spanning 12 feet?? There isn't much you can do without stripping at least one side of it. I would probably remove the ceiling, put in new 2x4s on both both sides of each existing joist, install a temporary beam down the middle, jack everything level, and nail/glue it all together. No reason to carry anything up and down the stairs...
David,
You would sister 2x4s to sagging 2x4 joists spanning 12 feet?
I wouldn't do that. I would sister on some 2x6s. Yes, you'll need a ramp at the threshold -- but what's the point of replacing sagging 2x4s with more 2x4s?
Martin, if you can convince him to lower the ceiling or raise the floor, I'll go with 2x6 or even larger. Of course it would be better. I'm just trying to keep it palatable here, since I think he was looking for a method of shimming on top of the subfloor, without getting into the framing at all.