A carpenter is hanging a solid core interior door weighing 35 kg (77 lbs). What is the minimum number of hinges and their approximate spacing required to adequately support this door and ensure smooth operation?

Question: A carpenter is hanging a solid core interior door weighing 35 kg (77 lbs). What is the minimum number of hinges and their approximate spacing required to adequately support this door and ensure smooth operation?

Answer options:

• Two hinges, spaced 300 mm (12 inches) from top and bottom. ✅ Three hinges, with the top and bottom hinges 280 mm (11 inches) from the door ends, and the third centred.
• Four hinges, evenly spaced along the entire height of the door.
• Two hinges, one at the top and one at the bottom of the door.

Correct answer: Three hinges, with the top and bottom hinges 280 mm (11 inches) from the door ends, and the third centred.

Explanation: For a solid core interior door of this weight, three hinges are generally recommended. Positioning the top and bottom hinges about 280 mm (11 inches) from the top and bottom of the door, with the third hinge centred between them, provides optimal support and prevents door sag. Two hinges are typically for lighter hollow-core doors, and four hinges are usually excessive for this weight.