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bobj3

Hi Berry

"My question is why not use biscuit joinery?"

Because we all have kids that get mad sometimes and the biscuit can't take it.
It's just a butt to butt joint so to speak with a spline that holds it as one.
Once the glue joint moves that's it,and it's going to fail, unlike mortise & tenon, it's hard to break the glue joint,because of the size and the amt.of glue use on this type of joint.

Bj

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Mike

Berry, biscuit joinery actually is a mortise and floating tenon joint. The reason conventional mortise and tenon joints are prefered for door frames is strength. When building the doors you want as much material as possible involved in the joint to reduce the likelihood of the door sagging or joint failure. It helps to think of wood as a bundle of straws held tightly together. Glue adheres well to grains running in the same direction or at right angles to each other like in plywood. End grain does not offer enough purchase for the glue to hold. Anything we do to increase the amount of glue surfaces makes the joint stronger. A butt joint has one glue surface. Changing this to a rabbited joint gives 3 glue surfaces. A half lap joint also offers 3 glue surfaces but with a much larger area hence stronger. A through tenon offers 4 surfaces and a regular mortise and tenon offers 6 glue surfaces. This is the reason you see stacked biscuit joints for added strength, 7 glue surfaces but a much smaller area. Needless to say, solid wood is stronger than glueing a biscuit across the grain, and this is why conventional mortise and tenon is preferred..

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Mike

Woodnut65

Hi Berry, Mike has given good info. Mortise and tenon joinery is a preferred method.
The joints can be made with a router to give a number of profiles on the stiles and rails. These are also made with a shaper, usually in a production shop. If you use a conventional mortise and tenon the stiles and rails are left square. Hope this helps.
Woodnut65