36 ft by 18 ft hall and parlor design, four bents, 15 ft posts, and five foot knee walls on second floor. what is the easiest method of supporting common rafters. I will have top plate connecting all bents and will use 2 by 6 for rafters. thanks for your help

Have you read Jack Sobon's book Build a Classic Timer Framed House? His design is similar to yours in regard to the dimension of 18'x 36'. He uses a tie beam from plate to plate using 18' tall posts. This reduces the outward thrust of the common rafters at the plates. And because of this there is no collar ties or common purlin holding up the rafters. Maybe you could review this book and reconsider your design. Good luck, Jim

I'm no engineer but my understanding is that a bearing ridge beam eliminates the outward thrust problem