I am about to begin reflooring the main level in the house. One thing
I know I'll have issues with is the fact that the floor is not level.
I could see/feel dips and rises through the carpet, so I know I will
have to adjust the underfloor to some extent.
I did a search online for some ideas of how to best level the floor,
but none of the articles I found were very good. For example, what's
the maximum thickness of leveling compound you should use? When
should you shim instead of using leveling compound, etc? What do you
do about rises right next to a wall (assuming the floor board actually
goes under the wall? What unexpected special cases might I run into?
Nails or screws? What about squeeks? etc
This is for the main level of the house, so I want to do this
properly, but I also have a time constraint. I'd rather not run into
situations at the last minute that I hadn't thought of. Does anyone
know of any good articles on the subject, or can anyone offer any
I'll second that bigtime. If the main floor is wavy, you start looking
in the basement. If you don't have the skill set to know what to look
for, pay somebody who does. If you don't want to pay for a 'real'
engineer, a gray-haired semi-retired master carpenter would probably be
I had a problem where an addition met an older area of the house, there was
a slight rise over a foundation wall and a drop on one side. I used leveling
compound to level the floor after using a #36 grit belt sander to reduce the
rise. Where I needed more than 3/4" of filler I glued and power nailed in
plywood filler pieces to reduce the amount of filler needed and to add to
the floor stiffness. Worked like a dream. Topped it all with 1/4" firply
glued down the the old plywood floor and filler. This gave a flat, strong
and level surface to nail the hardwood flooring onto.
No more adding. The problem was caused by a ridge forming when new wet
joists were installed next to old dried joists. They started out perfectly
level but as the new ones dried out they shrunk in height. They couldn't be
jacked up to level them with the old joists because they were nailed and
bolted in place with many utility items in the way. Originally carpeted, it
didn't become apparent until the carpet was removed. The floor needed
leveling in order to install hardwood flooring which would not be able to
negotiate the ridge.
You need to determine why your floor is "wavy"...
You could have uneven settling, problems with the building being
under-structured for the load or issues with the methods used to
attach the structural members together when the home was built
which are now weakening things...
Joists should be adequately supported by resting on the foundation
or by means of being attached to a beam using a joist hanger...
If it is your joists which are sagging due to age you can try
new joists next to the older failing ones...
This is something that to do correctly is not a DIY task unless you
are an experienced carpenter...
The bumps I have are not huge, its just that they would be visible if
I have a nice shiny floor on top of them, and I don't want to go
through all the work of putting a new floor on if I'm going to be
disappointed at the end. Having taken the carpet off, it seems my
problems are limited to one specific area, which is below the
stairwell. There aren't any ants, molds, or other alarming things in
the area -- I can see some of the joists from below. It just looks
like there was some shifting over the years, but I'll know more once I
take the actual floor board off. There is another section, right
beside the main supporting wall there is a bit of a dip down. That's
a little more concerning, but again, I'll know more once I take those
floor boards off as well. It looks like I will have to reinforce the
area underneath a bit before I continue though regardless.
Umm... When solving "dipping floors" it is actually much more
effective to examine the problem from below so you can see
which structural elements aren't doing their jobs properly or have
settled/become detached/bowing/etc. as it is *impossible* to
see those defects from above the floor even if you remove the
finished layer of flooring to expose the sub-floor...
Getting in late on the discussion.
After my house was built, I noticed a distinct hump in the LR floor.
Tested with a level and various smooth balls that rolled away from the
hump in all directions.
It seems that one floor joist was installed correctly with the hump side
up, but the hump was much greater than normal.
I went down in the basement and found the offending joist.
I then took a reciprocating saw and made 3 cuts maybe 6" apart in the
center of the offending joist from the bottom to about 1" from the top
of the joist.
Next, I went back to the LR and jumped on the floor above the offending
I heard a crack, and the floor was checked with the level and the ball,
and was level.
I then sistered a 2x6 to the cracked joist.
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