All the suggestions above are worthwhile.
From Google
Red pine timber, when used in-ground, requries pressure treatment (typically H4 or H5 rating) to last 15–30 years,
as untreated, it is only moderately durable and susceptible to decay.
- Will you treat the timber?
I have a few questions and comment though:
- What is the issue with manufactured items, there are many great ideas around?
- The old ways are not always the best, compared with modern fixtures etc.
- Metal brackets set into the concrete as suggested above may be a faster method, thought about it?
- Will you insulate the walls and roof?
- How deep is your frost zone?
- Posts in the ground will improve stability if cross bracing is not used.
- In Australia I would use steel posts, set into the ground at each corner to start, then use timber above the ground for intermediate columns, on piers.
