Published
The snow-load number you hand the truss supplier - and the drawings that come back
The number has a name, and the name is the whole conversation
Every roof in this corridor gets designed against a snow number, and the county prints one on its own paperwork. But the number you hand a truss supplier is not the number that comes back on the drawings — it is the starting point. The Structural Building Components Association, whose members design the trusses, put it this way in a piece dated 13 March 2025 and retrieved 16 October 2026:
“Ground snow loads are the starting point used in determining roof snow loads for structural design.”
— SBCA Components, “Shoveling Through a Blizzard of Confusion” by Greg Greenlee, P.E., technical director. Retrieved 16 October 2026
Between your ground number and the truss sits arithmetic the industry does not leave to chance:
| The number | What it is | Who owns it |
|---|---|---|
| Ground snow load | The starting figure for a site — what the map and the jurisdiction give you | The building designer, from the authority having jurisdiction |
| Roof snow load | Ground load converted for the roof, exposure, thermal and importance factors | The building designer hands it to the truss designer |
| Service level (ASD) | Loads used unfactored against allowable stresses | ASCE 7-22 figures are service level |
| Ultimate level (LRFD) | Loads increased by load factors against factored resistances | ASCE 7-16 ground figures were ultimate level |
The conversion is not a rounding detail:
“This is different than the IBC, which utilizes a factor of 0.7 to convert ground snow loads into roof snow loads.”
— SBCA Components, March 13, 2025. Retrieved 16 October 2026
So a ground figure handed over loose can be designed as if it were already a roof figure — or the other way around, which is worse.
What Fremont County asks to see
The county’s preconstruction checklist, retrieved 14 August 2026, puts truss designs inside the permit itself:
“Two sets of detailed plans and supporting documents (Engineering Calculations) and truss designs are required before approval of permit.”
— Fremont County preconstruction checklist. Retrieved 14 August 2026
And it bolts an engineering trigger to its printed roof-snow-load figure:
“All structures built within a 70lb/ft…are required to be designed by a structural engineer or an architect that is licensed in the state of Idaho.”
— Fremont County preconstruction checklist. Retrieved 14 August 2026
Four more of its requirements shape what lands on the truss supplier’s desk:
- Paper size is a rule, not a preference: plans must be submitted on a minimum of 11 X 17 paper.
- Free-standing post and beam structures require engineered, stamped plans — stamped is the operative word.
- Review takes calendar: once started, the county warns it can take approximately 4 to 6 weeks to review and approve building plans.
- The design professional must be Idaho-licensed — the checklist names the state, not just any stamp.
What that 70lb/ft line means for which lot is its own story — we have told it here, with the 115 PSF subdivision case and the Chester-and-Marysville split alongside. This page is about the conversation those numbers start.
The mistake the industry is loudest about
SBCA’s warning is blunt about what happens when the load level is misread:
“If a service level load (ASD) is provided and it is entered into the software as an ultimate load (LRFD), the loading on the truss will be less than intended, resulting in a dangerous unconservative design.”
— SBCA Components, March 13, 2025. Retrieved 16 October 2026
Same number, wrong bucket, weaker truss — and nobody downstream sees it on the drawing. The context makes it live: “For example, Idaho has adopted the IBC without amendments to Chapter 16 structural design” — and between code cycles there are five different ground snow load figures that could be in play, per the same article. That is why the fix is paperwork, not heroics:
“The best practice is for the building designer to provide the truss designer with the design criteria, including which code and standard were used to determine the design loads, so the truss designer can properly apply the loads in the truss design software.”
— SBCA Components, March 13, 2025. Retrieved 16 October 2026
What comes back on the drawings
The paper trail runs both directions — the county reads the same sheet you do:
“The truss design drawings should then provide the design criteria used in the truss design, including the design loads, so the building designer and the code official can verify the truss was designed appropriately.”
— SBCA Components, March 13, 2025. Retrieved 16 October 2026
In practice, before trusses are ordered, the file you can put your hands on should show:
- The design ground snow load for your site and the code version it came from — IBC chapter 16, ASCE 7-16 or 7-22, stated in writing.
- The applied roof snow load after conversion, with the 0.7 factor visible in the arithmetic.
- Load level labeled — service (ASD) or ultimate (LRFD), so nothing is entered in the wrong bucket.
- The Idaho license of the engineer or architect whose calculations carry the county’s 70lb/ft trigger — verifiable, like any credential.
That sheet is what the county permit actually reviews, and it is what answers the question a lender or an inspector asks years later. Heavy-timber and log packages play the same game with different pieces — that systems page covers theirs.
Sequence it like a builder
- Nail down the site’s design ground snow load in writing — jurisdiction figure, code, edition — before anyone quotes trusses.
- Pass the whole design criteria to the supplier, not just a number: code, standard, load level, and the building designer’s name.
- Order the truss drawings early enough to survive the county’s 4-to-6-week review window inside your permit schedule — winter makes it longer, not shorter, and cold-weather pours have their own calendar.
- Read what comes back: the design criteria block on the drawings should state the loads and their level, and the engineer’s Idaho license should be on the stamped pages.
- Bring us the plans and the lot — we will put the whole package in front of the right supplier: (208) 656-1516.
A truss is one of the few parts of a house that arrives with its own biography — designed against a named load, checked against a named code, stamped by a named engineer. The buyer’s job is to make sure all three names are on the sheet.
Common questions
What snow load do I give my truss supplier?
Not a bare number. SBCA's stated best practice is for the building designer to provide the truss designer with the design criteria - which code and standard were used to determine the design loads - so the loads are applied properly in the design software. Hand over jurisdiction, code edition, ground load, and load level together.
Is ground snow load the same as roof snow load?
No. Ground snow loads are the starting point used in determining roof snow loads for structural design; the IBC utilizes a factor of 0.7 to convert ground snow loads into roof snow loads, with adjustments for exposure, thermal condition, and importance. Handing a ground figure where a roof figure is expected overdesigns; the reverse underdesigns.
What is the ASD versus LRFD trap SBCA warns about?
ASCE 7-22 provides service level (ASD) ground snow loads while ASCE 7-16 figures were ultimate level (LRFD). If a service level load is provided and entered into the software as an ultimate load, the loading on the truss will be less than intended - SBCA's words: a dangerous unconservative design. The load level must travel with the number.
Does Fremont County require engineered truss designs?
Yes. The county's preconstruction checklist requires two sets of detailed plans and supporting documents (Engineering Calculations) and truss designs before approval of permit, states that structures within its printed 70lb/ft roof snow load must be designed by a structural engineer or architect licensed in Idaho, and requires engineered stamped plans for all free-standing post and beam structures.
How big do plan sheets have to be?
Plans must be submitted on a minimum of 11 X 17 paper, per the same checklist. It sounds trivial until a set comes back printed small and the county declines to accept it mid-review.
How long does county plan review take with truss designs?
The checklist warns that once started it could take approximately 4 to 6 weeks to review and approve your building plans. Truss drawings are part of that package, so order them early enough to survive the window - especially heading into winter.