I have a 1920s house I am remodelling and got to the floor phase.
Decided for hardwood. Problem is that the upper floor sagged about
1/2in (in the center) over the years and I cannot push the floor back
The hardwood planks are about 5/8in thick and 3in wide.
Right now I am considering two options.
1) get laminated wood in several different thicknesses, cut strips and
screw them to the old floor trying to eliminate or, at least, reduce
the sagging to a minimum and then nail the hardwood planks to them.
2) pour self-leveling compound and then glue the hardwood planks to
the cement, as suggested by a friend, but I am not very fond of this
Anybody has experience with this problem and how it was solved?
Thanks in advance!
Cannot bring the joists up (straighten them) because that would mean
pushing the walls, ergo the ceiling and roof, also up. The sag is
controlled by new beams and columns so the floor will not sag
No you misunderstand my suggestion. You don't try to move or straighten the
existing joists. You just add sister joists along side. Drill through both
and bolt together. The sister joist will stand 1/2" above the old one in the
middle and flush at the walls. Fix new floor to flat sister joists.
I was assuming the floor sheathing was in place. Obviously, you don't
want to remove and replace it for your fix. If for some reason it
isn't, I would suggest shimming the top of the bad joists would be
easier than bolting on a sister.
Thanks much! However the subfloor is already in place and removing
it would be a major headache, besides the project delay. Whatever I
do must be over the existing subfloor.
I can try to replicate "dummy joists" over the existing subfloor and
nail/glue a laminated wood new "subfloor" over them. That will take
a lot of work but is likely faster than removing the old one.
Gluing the hardwood planks over self leveling cement seems to be the
easiest/fastest route but I do not know if it can be done without
risking damaging the hardwood planks or making the floor squeaky.
It would be a much greater project delay if you have to rip up all of the new
hardwood flooring because it failed. The only solution that has been offered to
you that is fail safe is using sister joists.
Of course you realize that to sister joists, he would have to remove
all the partitions, all the subfloor, sister joists, redeck, reframe
partitions, drywall etc or he risks floor failure (which would be
what--a few squeaks?) . This is not a realistic approach to fixing a
1/2" dip in a floor.
He would only have to remove that part of the subfloor that is sunken.
Do you know for a fact that he can glue 5/8" thick hardwood flooring to leveling
cement? That's what he is proposing. Hardwood flooring moves a helluva lot.
Another problem with sistering joists is that there could well be
wires crossing the joists, it being a second floor and all. Have to
move the wire or notch the new joist somehow. Also, there could be
bridging and blocking you'd have to remove--yet more work. Also, the
OP is talking about eliminating the sag near doors. So you are
suggesting he rip the subfloor around partitions, under doors, and
somehow sister new joists in these areas?
You can glue hardwood to concrete. I've seen it on directions for
3/4" strip hardwood flooring. I haven't done it, so I'm not going to
suggest it, and the OP seemed resistant to the idea anyway. If it was
mine(and I underwent a personality change so I couldn't stand leaving
it a sag in a floor in a 100 year old house) I'd cut some shims to
flatten, screed in some webcrete floor leveler between the shims, and
staple the floor through the shims. Most places it'd probably work to
staple right through the leveling compound anyway.
Also regarding "self leveling compound", I don't know of a floor
leveler that is actually self leveling. That is, you can't stand in
the middle of a room and dump it from a bucket and VOILA it's level.
you need to get down on your hands and knees and work it. In your
case, you'd probably want a long straight edge to sort of screed it.
Yes. The sister joists have no need to be load bearing joists. They would be
put there for the sole purpose of raising the floor back to level. They can be
2"X4"s and can even be cut in sections to fit around wires, etc. Seems like a
10 to 20 hour job to me. If were my house and I felt that the floor had to be
level (which I wouldn't) that is the way I would go. That way there would be no
future concerns of loosened flooring or buckling.
This site suggests it might be possible to lay decorative cement over wood
but recommends applying "metal lath or diamond back mesh with a staple gun
or staple hammer first.
I still don't like the idea though.
Regarding option one, I'm skeptical of the practicality of that. How
would you decide what thickness where? Wouldn't the thickness have to
vary on at least some of the strips. I've thought before of screwing
down a 2x2 and snapping a line at level, and then removing the strip,
sawing it, and reapplying it. Sounds like a ton of work. I think you
would have to fill the spaces between the shims with floor fill or
something. Liable to get a lot of squeaks.
There have been other posters on this group who have inquired about
nailing hardwood down over self-leveling compound. Not sure how it
turned out, but I really think that it might be the way to go.
The option you don't list is leaving the floor as it is. It is a 90
year old house after all. Part of the character of an old house is
dips in the floors IMO.
I thought about leaving as is but it would look really terrible. I
can live with minimizing the sag but have to eliminate it at least
where the doors are. I tought about getting different laminate
thicknesses and nail/screw them over the wood strips of different
That would give me a relatively flat surface to nail the hardwood
planks to. It is a lot of work indeed, ergo the questions about
laying cement leveler and gluing the hardwood planks instead of
How does glue work with hardwood floor meant to be nailed? What could
be the problems coming out of doing so?
Look into the possibility of using a self-leveling floor compound to
improve level on the subflooring. This would be a thin layer of
concrete, in effect, that would shim the difference you need. Nailing
through it might be a trick, but given the thickness, probably not.
Anyway, it's just an idea, and potentially an easy solution.
I didn't see any mention of the ceiling below sagging 1/2", does it ?
The sister joist is the only sure and sensible fix.
No need to thank for suggestions since your not using any of them anyway
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