They look hand scraped as well. Is that correct? Is the dip visible from a standing position? Have you talked with your contractor? I like the finish color BTW.

How old is the house? What type of substrate is it glued to? How much preparation work did the Contractor/wood flooring installer do (was paid for) prior to the wood floor being installed?

Is your home sitting on posts/pillars? What is sitting underneath the hardwood? A basement? A crawlspace? Garage? A dip that just appears can mean some settling of the home...this can be normal or it can be big issue.

When you step on the wood that is over the 'dip', does it move? Does it feel like it is moving or shifting? Does it sound/feel hollow?

A bit more information about the WHOLE home construction as well as where in the HOME is this dip.

jsfreud , we may only be able speculate. It sounds like you really need a flooring contractor to come out and investigate this in person.

It might just be the hand scraped feature. Do you have a straight edge that you can put across it?

Pencil is not a straight edge. Pressure from your hand can cause it to lean towards the eraser side. The pencil maybe sitting on a high spot of the hand scrape.

" and maybe a screw from under the floor could pull the planks down."

Or split them in half if there is an object of some sort holding the flooring up. I would want to know the issue rather than a rube goldberg half ass attempt to fix it.

My main thing is if he is speculating and he has been to the site anyones guess here will be even more of a wild ass guess.

I bet the installer did not abrade the Advantech and the adhesive is pulling off the subfloor.

It is only horrible, if, not done properly.

Assuming that your OSB is Advantech. The sealer on the Advantech needs to be abraded off with a 40 grit. Then a paintable moisture barrier needs to be applied, then the glue down process can begin.

Glue selection is now critical. The industry is leaning towards Silane base adhesives. The old polyurethane adhesives turns brittle and can snap off the substrate over time. Silane stays flexible. Another example of what use to work, does not work anymore.

G&S points out something that was bothering me about this install: OSB + Glue. Like G&S I'm HOPING the OSB is Advantech....but it might not be. And that's a whole 'nother can of worms.

IF (big if) this is normal OSB (like the builder threw it down without knowing the final floor finish) that goes underneath carpet of floating flooring, then it might not be the "good stuff" like Advantech.

OSB is FULL of glue and WAX...yep...wax. And just like wax from a candle, the wax in OSB can create bond problems with other adhesives. The reason why Advantech can be used in a GLUE DOWN install is the ability to abrade it (not many OSB products like to be sanded...they can get chewed up pretty quick).

I'm not saying this is an adhesion issue. Without seeing how much movement that area has (you would know if the glue has let go...you would step on the boards and then would bend down under your foot like a trampoline), we are only guessing at adhesion issues.

But what it does tell us is the METHOD or QUALITY of the build. Regular OSB as a subfloor underneath a glue down engineered hardwood shows a builder trying to cut corners.

Now...a house built on sand with pillars in some areas but not others and a wood floor that has a sudden "hump" or dip that runs the length of an entire room. I'm going to bet dollars to doughnuts that the "dip" coincides with a joist. And that leads us to the next concern...settling.

IF you are REALLY concerned about settling, you are welcome to reach out to a structural engineer. Before you do that, you will want to have ALL the soil testing results in-hand for your first interview. These should be part of the build or part of your ownership papers. You would have paid for it at some point (?built into the build price?). Go ahead and dig those out before reaching out to such a professional. If you don't have them or don't know if they were done (I'm not going there just yet...sigh) that's OK. The structural engineer can dig them out from city hall/building permits, etc....it will just cost a snick more in fees.