Laundry room on third floor in 3 story homes?

I just bought a three story home in the Heights. I have wood floors on second and third floor. My laundry room is on the third floor. I have a front loading washing machine (that has recently been checked out by an LG Technician and is in great working condition). My problem is: the entire house vibrates when it's on the spin cycle (even with anti vibration pads under the washing machine. And yes the loads and machine is also leveled) . But the shaking is kind of scary. I am worried for the structural integrity of the house. There are SO many 3 story homes in Houston that I figured someone would have some advice on this. HELP!