We're redoing the flooring in the whole house. We have existing hardwood which is in decent shape. a few scratches here or there that could probably be fixed. No buckling or anything. Maybe one or two spots where it feels like the floor should be nailed down again where a plank or two is loose. No noticeable squeaks or anything.
Pretty sure the hardwood is original to the house which means it was installed about 70 years ago. There are planks about 2 inches wide and then some that are around 4 inches. From what i can see, it looks like there's no underlayment under the existing hardwood and it was just nailed on top of the wooden subfloor. The only place that is different is the kitchen. Flooring in there had to be removed so it's down to just the bare wooden subfloor.
We're going with a laminate wood floor from republic floor. Contractor picked up 3mm underlayment. I don't really know much about underlayment, or installing floors in general. Just wanted to know if there's anything specific i should look out for while they do the install and if 3mm underlayment is ok or if i should get something different. Or anything else I should do/look out for/make sure is done etc.