A door frame consists of three members; two upright posts secured at the top with cross piece called the head.

The nominal sizes are 100x75mm and 125x75mm

The head and the posts are joined together by a tenon & mortise joint the variations of which are:-1. Closed mortise and tenon joint.2. Haunched Mortise and tenon.3. Draw pinned slot mortise and

tenon joint.4. Double tenon.

A DOOR FRAME

Proportions of a tenon:-1. Thickness of tenon

should be 1/3 that of the member.

2. Width of tenon should not exceed 5 times the thickness or a maximum of 125mm whichever is less.

Wide tenons should be avoided because:-

1. Shrinkage can cause wedges to become loose.

2. May bend when wedges are inserted splitting the mortice.

3. Require long morticeswhich will weaken the joint.