Every framing package we build in Minnesota starts from one number: ground snow load. The Minnesota code sets it at 50 pounds per square foot across the southern half of the state and 60 psf in the north. North Dakota runs off the ASCE 7 maps instead, with most of the state landing between roughly 30 and 50 psf. Those numbers — and how your engineer converts them into roof loads — shape more of the framing package than almost anything else on the structural sheets.
Ground snow load vs. roof snow load
Ground snow load is the code's baseline: the snow weight expected to accumulate on open ground in a rare, severe winter. Your roof doesn't see the full ground value. The engineer applies factors for exposure (windswept vs. sheltered), thermal condition (heated building vs. cold storage), roof slope, and building importance, and the flat-roof design load typically comes out around 70 percent of ground. So a 60 psf ground load in northern Minnesota usually becomes a roof design load in the low 40s — before drifting.
Where the numbers get big: drifting
On the buildings we frame, the uniform load rarely governs. Drift loads do. Anywhere wind can pile snow against a vertical surface, the code requires designing for a wedge of drifted snow that can run two, three, sometimes four times the flat-roof load:
- Stepped roofs — a three-story residential wing meeting a one-story clubhouse is the classic multi-family drift condition.
- Parapets on flat-roof commercial buildings.
- Rooftop units and screen walls large enough to catch blowing snow.
- Lower roofs beside taller structures, including snow shed or drifted off a neighboring building.
Unbalanced loads on gable roofs and sliding snow onto lower roofs get checked too. If your building steps anywhere, expect heavier framing at the step.
What this means for the framing package
Snow load isn't an abstraction on the truss sheets — it lands in the lumber:
- Trusses. A truss designed for the 60 psf zone carries bigger chords and more plate steel than the same span further south, and drift zones get dedicated girder and drift trusses.
- Headers and beams. Every pound on the roof travels down. Long garage-door and storefront headers in the north zone commonly land on LVL or steel where SPF might have worked in a lighter zone.
- Bearing continuity. Point loads from girders need squash blocks and stud packs stacked floor over floor all the way to the foundation. This is where plan-table shortcuts get caught in the field.
- Wood vs. steel decisions. Heavy drift loads at mixed-height buildings sometimes tip a lower roof toward light-gauge steel or a hybrid system — we walk through those trade-offs in our wood vs. steel framing guide.
Snow load during construction
One thing the design maps don't cover: the half-built condition. Trusses that are set but not fully sheathed and braced are nowhere near design capacity, and a wet 8-inch snowfall on an unbraced roof system is a genuine collapse risk. With the first plowable snow only weeks away, this is worth planning now. Our crews run permanent bracing and sheathing tight behind the setting crew all winter, and we clear decks before stocking material on top of snow — it's a sequencing discipline as much as a safety one, and it's baked into how we build a multi-family framing schedule.
What to check on your next set of plans
Go to the structural general notes and find three things: ground snow load, flat-roof snow load, and a drift diagram for every roof step. If the building steps and there's no drift diagram, ask the question now. A drift truss added during design costs a change order; one added after an inspector flags it costs a schedule.
Framing a project in 50 or 60 psf country? Send us your plans for a free quote — we've framed 1,000+ units under Minnesota and North Dakota snow loads, and we bid what the drawings actually require.