Are these traditional timber joints strong enough for a heavy snow load?

Checking in 12-inch Nordic pine is almost a guarentee, especially with the high moisture content you're starting with. It looks scary when those gaps open up, but as long as the check doesn't spiral or run trough the heartwood in a way that compromises the shear strength of your joinery, it's mostly aesthetic. Pine dries from the outside in, and that tension has to go somewhere. The structural integrity of a timber frame ussually relies on the bulk of the material, not the surface.

Stick with the **drawbored mortise and tenon** over the hidden screws. When that pine starts to shrink over the next few years, a structural screw can sometimes become a pivot point or even snap if the wood moves with enugh force. A drawbore actually pulls the joint tighter as the peg and the beam dry together. You want that mechanical connection. If you're worried about the scale, just use a power drill with a ship auger bit to hog out most of the mortise waste before you clean it up with your chisels. It'll save your shoulders. For those brutal Norwegian winters, the load-bearing capacity comes from the housing of the joint, not just the fastener. Make sure your **shoulders are square** and fully seated. If you rely solely on screws, you're putting all that snow load onto a few steel shafts instead of the wood's own grain. If you realy want a safety net, you can use long structural screws to pull things into place during assembly, but don't let them replace the actual joinery.

And honestly, doing this solo is a slog, but it's doable. Use a chain mortiser if you can rent one, but otherwise, focus on your layout lines. If the joinery is tight now, the drawboring will handle the rest as the seasons shift. That pine is going to move, but a well-pegged frame will move as a single unit rather than pulling apart at the seams.

I'm just starting out with smaller bench projects, so the idea of 12-inch beams is wild to me. When you do the drawboring, does the peg material have to match the pine? I’ve heard about people using hardwood pegs like oak even in soft frames, but whould that cause issues with how the wood shrinks over those Norwegian winters?

Also, for a guy working solo, is there a trick to keeping those big auger bits straight? I’m worried about my drill wandering and ruining the alignment before the chisel even touches the wood.

On the peg question, definitely go with kiln-dried oak or ash. You want a material that won't shear. Pine pegs in pine beams are too soft for a drawbore; you’ll just crush the peg before it acutally pulls the joint tight. Just make sure those pegs are bone-dry—way drier than your pine—so they don't shrink and rattle later.

For drilling those deep holes solo, use a simple wooden jig block. If you're off by even a degree at the start, you'll miss your exit mark by a mile on a 12-inch beam. I usally clamp a thick scrap block with a pre-drilled plumb hole to the beam face to keep the bit from wandering.

Since you're dealing with high moisture in those 12-inch beams, slap some end grain sealer on the posts before winter. It won't stop checking, but it slows the drying at the ends so your mortises don't split or warp while you're still fitting things. Working solo, you'll want a heavy-duty come-along or beefy ratchet straps. Trying to manhandle that much pine into a tight joint by yourself is a recipe for a blown-out back. Use the straps to snug everthing up and check your fit before you drive those oak pegs home. It makes a massive difference when you don't have a crew to help muscle the frame togehter.

To manage those 12-inch checks, you might want to try kerfing the hidden faces. If you run a shallow saw kerf down the length of the side that won't be seen—like the top of a tie beam—it encourages the wood to split there instead of on your pretty faces. It's an old trick for heavy timbers that are prone to heart-center checking.

Also, since you're solo, keep an eye on your "relish" (the wood past the peg hole on the tenon). If that pine is as wet as you say, don't get too aggressive with the drawbore offset. An 1/8 inch is plenty. Any more and you'll just blow out the end of the tenon when you drive that oak peg home.