When sourcing wood frame sofas, the internal construction is more critical than the exterior finish. Prioritize kiln-dried hardwoods (such as Oak, Ash, or Walnut) because the kiln-drying process removes moisture to prevent warping, cracking, and fungal growth. For the joints, avoid frames held together solely by glue or staples; instead, look for mortise-and-tenon joinery or corner-block reinforcement secured with industrial screws. Ensure the wood surface has a smooth finish with non-toxic, lead-free coatings that comply with international safety standards.