Sill with scarf joints over post foundation

[Rait]

Hello, sorry if this has been asked before but I could not find the answer  ???

I'm planning on building modified Sobon shed - 14x19 feet. We do have frost here (up to 4 feet), so my plan is to do kind of traditional foundation (in here slab wall with rubble trench was used for log houses last century) - rubble trench with 6 concrete posts. On the 19 feet walls, the sills need to span about 9 feet. If use calculator with required floor load and span, I could get away by using 8x8 pine. However if the sawmill says 19 feet is too much, I might need to use scarfs. In this case however should I be looking for 8x10 sills or do 8x8 with shorter span (so 8 posts instead of 6)? As Sobon shed has 3 bents, I guess it makes sense to have post directly under each of the posts too, cant do that if I need to go 8 with posts...

[Jim_Rogers]

If your load calculations are correct then use 8x8 and put the scarf off to one side of the center posts. Put foundation posts directly under bent posts.

Standard rule on scarf sizing says the overlap of the scarf should be 4 times the thickness of the timber. So your scarf overlap should be 32".

Jim Rogers

[Rait]

Thank you, i think ill go with 8x9 if he cant do 19+feet timber.