My wife and I, four months ago moved back into our rebuilt house, after it was destroyed in a fire.

We are noticing that the laminate floor, especially in the living room, is sagging
In some spots.
I assume that this is something that the contractor is accountable for.

I agree. Take pictures and be persistent. Did your insurance co pay the contractor? Contact them too if so.

Maybe, but laminated floors also sag whenever they've had some sort of water damage as well. Be sure to check for any busted pipes under your house.

Maybe, but laminated floors also sag whenever they've had some sort of water damage as well. Be sure to check for any busted pipes under your house.

Thanks guys-- however,

a) I don't think the sag is to a degree that can be captured with a photo.

b) Don' think it's water damage---however the same type of floor eventually sagged badly prior to the fire---the contractor said it was because there was not enough ventilation in the crawl space underneath---he widened the holes in the brick surroundingthe crawl space

It will take a lot of work examining the crawl space floor and walls, soil in your area, drainage around the house, and ventilation. And you don't want holes in your foundation unless they are filled with screened vents, to prevent animals and bugs as much as possible.
The contractor isn't liable for prior conditions that weren't part of the fire and rebuilding, but how does he know what the floor was like before the fire? How old is the house? Did he build it?

Thank you

Yes the contractor rebuilt the house and floor--- this house was built in 1946, but obviously not by the current contractor---the new contractor was aware of the same floor problem prior the fire.