Building a timber frame home

Hello all, I live in Canada and run a small sawmill during the weekends. I've been stock piling 5x8 and 4x4 beams for a house project I will be building in the near future. The house is being designed by me in a program called Sketchup and is a standard rectangle home. I recently put up a 20x20 barn and that took me a summer to erect. The house is a more extensive and will be 32x49. The foundation will be a full foundation with 8" walls and floor with frost walls going 5ft. This will be hired out with a local contractor which I plan on putting the subfloor on and storing the beams in the foundation to dry out for a few years.

Question, the roof rafters are quite long (5x7 at length of 25ft). The spread will be 3-4ft apart on each rafter. My concern is the length and if a scarf joint can be used to make up the size? My mill will cut 20ft but 25ft is very long and will require me to remove a wall in my mill house to add an extension. The extension will allow me to mill 35ft which is more than enough. The pitch of the roof is 20x20 pitch.

Thank you.

I would not use a splice in a rafter unless the splice fell under a purling or support system of some kind, like a wall. Then, either but them over the purling or by pass them next to each other, or some such fixation.

Long mill track is great for long stock and multiple logs or log and edge at the same time.

Typo on the 20/20 pitch, 12/12?

Yes sir, 12/12 pitch roof. I ended up extending the sawmill so now I can cut 35ft. Should be able to get everything I need done now. Currently have the frame how I want it in sketchup so now I need to get cutting. Walls will be 12ft with the second floor started around 9ft. The 12/12 pitch should give me enough room for a 1.5 story home.

Jumping in here late, but is a foundation a good place to dry your timbers? Maybe I misunderstood?

It would be good to keep the rain off the timbers but to dry correctly it needs some air flow. The timbers will only dry until the air in the storage area is saturated with moisture. Then they will not dry, and could cause mold.
I would put in a dehumidifier to dry out the air.
Jim Rogers