Subfloor preparation is critically important for any DIY flooring project. Your subfloor should be flat within three sixteenths of an inch to ensure planks lay evenly and lock securely. Uneven surfaces cause gaps, squeaks, and premature wear. For LVP and laminate, obsessing over flatness by sanding, filling low spots, and cleaning thoroughly is key. Taking extra time for prep avoids costly mistakes and ensures lasting durability, especially in pet-friendly homes. Proper prep also eases installation, improving the final aesthetic and performance.