Common mistakes when installing luxury vinyl plank flooring over hardwood include neglecting to fix squeaky subfloor movement, skipping expansion gaps, and failing to use a proper underpad. These errors cause trapped squeaks, floor buckling, and reduced durability. The best practice is to secure loose boards and joists first, install a quality noise-reducing pad, maintain expansion gaps, and only then float the LVP to assure a stable, long-lasting floor.