There are really no "great" options with an unlevel subfloor. Carpet or sheet vinyl would probably be the most forgiving, but keep in mind any imperfections in the subfloor will just telegraph to the surface with these solutions.

It is true that click floors are in some ways the toughest to use with uneven subfloors, as it doesn't take much movement for the click mechanism to come loose or break. But really, unless you are open to the idea of very wavy looking floors, your best solution will be to figure out a way to level the subfloor.

As far as laminate, I would suggest you consider looking at nicer quality vinyl plank. It looks just as good, and is waterproof and much more durable. Here are some examples from the Modin collection:

Did the contractor's say that leveling compound could not be used? Anything that you use that is linear is going to have an issue - wood, laminate, LVP. They cannot be applied on an uneven surface. They will come apart. Can the subfloor be redone and things flattened? Otherwise, carpet is your best option.

our kitchen floor and adjacent back hall were tremendously unlevel (145 year old house) and our Amazing Tile Guy still managed to do black and white checkerboard perfectly. he floated the underlayment on incredible amounts of goop underneath, we couldnt walk on them for a day or so, and then did tile with quite a bit of goop too. came out lovely.

so talk to your floor person as to whether you can do something other than nail dow your underlayment.

You are between the proverbial rock and hard place. It is a shame that this was not addressed before/during the kitchen remodel. You can't do the kitchen without impacting the remodeled area.

The contractors are giving you proper advice. It can be handled different ways. IMO, the best way technically to correct it would be to sister joists in to flatten the space (level and flat are not the same thing) and install new subfloor - we use AdvanTech 3/4" T&G subfloor. The floor joist spans should be examined and possibly additional support added to prevent further sagging of the floors.

What nngirt is describing sounds like floor leveler (goop). I would do some asking around and see if it can be applied in two-three stages so that it dries properly between each application. The first coat or two would be put into the deepest dips only and those built up until the final coat goes over the whole floor. Will take longer which equates to more expensive than one coat, but may work. We have not done that, but that is what one would do with sheetrock compound when trying to fill a hole. At least worth a discussion. What you need to be careful about is that you are trying to even out ridges and valleys in the floor (called flattening). Actual leveling of the floor could mushroom and create other issues - as we have seen a floor can be out of level so far that the leveling compound would be 2-3 inches thick at the other side of a room and doors would not open and any abutting flooring would not be at the same height. You don't want to get into that problem.

I have not heard structural supports called pony walls. I understand that this might be a good thing overall, but that alone does not seem that it would even out the floor. It might be necessary to prevent further sagging. I also don't think that just replacement of the OSB is sufficient to prevent unevenness down the road.

Great point. I just want the floor flat not level! :)

I guess we will just compare cost. The sistering of joists sounded best to me for all the rooms. Our joist are 16" apart and our room is 16x22 so a pony wall might be better in the long run. Its a two story house, so lots of weight.

Would the pony wall "lift" the sag? If so, would it crack walls and create havoc on my doors (new stress points)?

The kitchen isn't affected horribly. There is a new island in the middle so at least it breaks up the room and we would just need to address the areas with longer spans.

*one more question* if we used leveling compound, how would nail down floor install over it? Would I use glue down instead? (if installing hardwood/bamboo)

Technically a glue in place cork floor can be used here...(it can be treated like a sheet product such as carpet, vinyl or lino). It can be glued to the BEAUTIFUL NEW PLYWOOD (if you are laying new subfloor) or over SLC (self leveling compound). You will still have dips and hollows but it can be done.

If you want a "rigid" or click together product you are in for an EXPENSIVE fix. Deborah is correct...it SHOULD HAVE BEEN DONE/suggested at the time of the kitchen install. Sistering the joints from underneath with help tremendously. Using jacks from underneath can be done. Laying new subfloor with HUGE amounts of cement (SLC) can be done...but that can add so much weight that you get MORE sag because the subfloor can't handle the weight. The SLC would be good if you choose to work with a floating floor (don't let them put extra padding underneath...it isn't a fun experience).

You may have to "fix everything else" and then deal with the kitchen as a separate entity for flooring (as not to disturb the new kitchen).

There are no easy answers. This is a photo of cork glue down tiles...they can wrap around a telephone pole. They can handle the dips.

@jenniferlindsay I'd like to comment on this. First find new contractors. Any descent Self Levelling Compound can be used to level upto 1" and it says that right on the bag. Mapei and Custom are decent brands.
Secondly the use of slc will dictate what type of flooring you use and how it will be installed.For example you can use floating hwd/cork/vinyl.
Also you can install glued down eng Hwd..Hope this helps. Do your homework ask what products will be used. Read the directions on the products.

If you have put a new island in the kitchen then you have added weight on already sagging support system. You may want to have that looked at and, if needed, addressed with additional piers and joists under the island area. If you want to address the overall problem and prevent further sagging, then I really think you will have to add support to the structure, sister in joists and install new subfloor. You can put support and jacks in and slowly move the floor back up, but you do run the risk of causing cracking in ceilings and walls. Needs to be done by someone who will take their time and you may not get all the way back up to original level. Good luck.

Re: the use of Leveling Compound (SLC)- perhaps the bigger concern for its use- if you don't improve the floors structural support- is flexing when walking on the floor. Question for PROS; will SLC offer any flexing and still keep adhesion to the sub-floor? Sounds like a future failure- especially for future tile cracks.

I know this is an old post but I'm glad it popped up again because we are dealing with a very similar problem. I'm curious what the OP ended up doing.

I have the same issue. Old house is stable but will not level due to joists and supporting beams having flexed and adjusted to settling of supports and they are "set" and even after jacking up will not straiten out. I am considering using thinnest under 3/4 inch plywood over existing floor in an attempt to make the floor flatter. Not worried about level as much as reducing the slope of the dips. Has anyone tried that approach? Then I plan to use Ditra to lay tile if possible.

There are lots of solutions to this issue but most are very large jobs. if you want a small job you lay down a flooring that works with the floor you have. In this case flexible flooring such as carpet, vinyl or cork sheets work well.
I buy, renovate and sell for a living in the UK and the floors are often 100+ years old. If the floor is fairly stable and you are happy to put a rug over the odd defect then you can lay almost any flooring down. I put soft wood planks flooring down at my parents house 15 years ago, much to my protest. The hallway developed a large crack between a couple of boards at 5 years that a rug nicely covers up, but all other rooms still look good. the floor in the hallway rises in the middle about 2 inches, other rooms probably more, but they are a lot larger. My parents had wanted wooden flooring for so long that they said they were prepared to take a chance, and live with any small issues.

Armstrong Prizm vinyl planks claim to work on "floors with some irregularity". Has anyone tried this products on an uneven floor? My hallway has a hump up the center.

I have installed vinyl planks in our old house it's floors are very un even and we used a self leveling cement. It has some dips but overall seems to be ok.

I realize this is a very old post but I am having the exact same issue. The floor is in the kitchen so carpet won't do. I'm thinking that the cork glue down planks might work? I was thinking of sheet vinyl but the telegraphing I'm sure would bother me. Any suggestions? Right now I have tile and can't rip it out. (I have a patient tenant, but not that patient). Jennifer, what did you use and how is it working out for you know?

any responses are welcome

thank you

Your problem will be the tiles that you can't rip out. So long as the tiles (what type of tiles?) remain, you will continue to have problems getting a new floor in place. A cork glue down tile (not a plank) are not allowed over vinyl. An existing tile floor (ceramic or porcelain) will have to be removed or they have to be covered in concrete to create a smooth surface for anything like cork, vinyl or linoleum to be installed.

. .

I just had rigid SPC vinyl planks installed. The floors are totally smooth, but there is a noticeable dip. The installer, from a very reputable company that honors it’s work, said it was not a problem. The installer was meticulous in scraping the floor in another area, after skimming it. The installer said the issue, a concrete slab subfloor, was at the joint pouring. One side is lower than the other. That explains why our barstools always moved to the left. Our planks were laid parallel to the slab joint, not across it. As a result, the interlocking pieces of the click installation, would take all the pressure. Would laying the planks across the joint rather than parallel, been a better choice? The company warrants its installation for as long as the manufacturers warranty. In this case lifetime. They are an old line family company, with sterling reviews.