sub floor (flooring, ceiling, light, rooms)

[cargoman]

I am in the process of planing to replace the flooring in several areas of my house. It is a newer home built in 2002 and is over a large crawl space. When I walk around some of the rooms there is the usual creak where the sub floor needs to be fastened better. But I am concerned about another thing. In areas of the home I can walk and hear the floor move slightly. It seems to be enough that I can here the wall and ceiling make a noise as it shifts slightly. This is very disconcerting because it seems like excessive movement. The house was purchased two month ago and passed the inspection so I do not fear a foundation issue. I am coming to realize that this house was a quick build and I am wondering if the joists are just under supported allowing them to sag a little to much when I walk over them. Anyone else ever experience this?

[K'ledgeBldr]

You're assuming a lot of things without any material facts.

Do some investigating on your own- go into the crawl space. What does it look like? Is there vapor barrier on the ground? Is there insulation between the joists? What is the size of the joists? What is their spans? What does the mud sill look like? Is there anything on the foundation walls?

...and on, and on, and on.

All of these things can have the potential to effect the structural integrity of the floor system.