Josh
I’ve been doing some research into the answers to some of your ‘basic’ questions.
First, years ago I asked an old carpenter friend of mine one of these basic questions. “When you’re given the dimensions of a house as 24’x36’, where are these measurements actually taken from?” He told me that these dimensions were of the house foundation, all sheathing was then added to the outside of these dimensions.
Now with timber framing this maybe also true. The only exception that I’ve seen is when you are enclosing with insulated panels. Sometimes there is a ledge on the outside of the foundation for the panel to set on.
Next, I checked in my book “A Timber Framer’s Workshop” by Steve Chappell and his drawing show the posts are included inside these measurements (24’x36’). Any posts in the center of a bent are measured to the center of the post. That is, if you have a 24’ wide house with a post at 12’ the center of that post is at the 12’ measurement. Regardless of the size of that post. I’m quoting a drawing on page 200 in his book.
This drawing is of a 24’x36’ Hammer beam cape, with three bays. One bay is 14’, another is 10’ and the last is 12’. With an open ceiling in between the areas of the 10’and 12’ bays.
As to how big are the beams of a house layout, from my past reading, and if I’m wrong, I’m sure someone else will correct me, you design the floor joists necessary to support the floor, based on the size of the span between supports. Then the timbers necessary to support the joists. If it is a summer beam it has to be bigger than the joists. Then the plates and posts to support the summer beam. Basically from the center of the room out, making bigger timbers each step out. And as you said the wood choice affects the size of these beams.
To answer your question “how practical are our current ideas?” I’d say ok. But don’t restrict your designer to the actual post locations, as he will need to place them where they need to be for the best support.
And “how much space should we allow for the beams in the floor plan layout?” Most drawings show (in plan view) the posts as squares or rectangles in the corners of the drawings, again inside the overall dimension of the building.
If this doesn’t answer your questions, possibly you should buy this book and review this drawing to answer more of your questions. I believe it is available at the Timber Framers online store. I’m no expert but I hope this has helped you. Good luck, Jim
