You will see, from both old and contemporary examples in the Pacific Northwest,
that the four corner posts support a frame which support the roof logs.
In the interior, the roofing material is the spoil from excavating the pit.
On the coast, the house boards are split from the multipurpose western red cedar.
The biggest house that Franz Boas measured was a Haida dwelling, 40' wide and 100' long.
The biggest single house board was a split of western red cedar, 14' tall x 36" wide x 3/4" thick ( no mean accomplishment.)
Haida stripped their houses and carried those house boards by boat as they moved around seasonal camp villages.
Regional differences in design and construction.