Think of how much weight is in a bathtub. If you put 30 gallons in it at 8 lbs per gallon, that's 240 right there. No person. Your refrigerator is much heavier with all that food in it, plus it has a smaller "footprint" than the elliptical, so the weight isn't distributed over that far of a space.
The ellipticals are designed to spread the force of the weight evenly over the space it occupies, which means that each board that is under you only gets a portion (probably 3 boards). You might not like it because of the noise below, but I doubt you'd have a problem with the structure of your house.