In a Maloof-style low back chair (https://americanart.si.edu/artwork/low-back-side-chair-34536), the back legs attach directly to the seat and to the back. The grain in the seat runs back to front, while the grain in the back runs sideways. It seems like the expansion of the seat would pull apart the back joints. Why doesn’t that happen? Do the legs flex enough to accommodate the pressure?
I am trying a similar approach (not in style, but in that the legs attach directly to the seat) and wondering if I should align the seat/back grain in the same direction. Wood movement calculator for my area (Portugal) says that a beech seat could expand by up to 1cm…
Below is a prototype in cheap fir, without the back installed as I agonize over this issue. (Yes, I know the leg joints are weak, the plan is to reinforce them with wooden or brass pins.)