Published
There is no published snow load for Chester or Marysville — and the ordinance won't tell you either
Two towns in this corridor with no published number
This site has written the corridor's snow loads in some detail: the Ashton District's 90 PSF, and the North Fork Highlands District's 115. Both come from the county's adopted ordinance, and both are checkable.
Chester and Marysville are a different situation, and it is worth being straight about it. Ask what the ground snow load is at Chester and there is no document you can point at that answers the question directly. Here is exactly why, and what to do instead.
The research has no station there
The University of Idaho's "Ground Snow Loads for Idaho" derives loads from recorded snow depths at weather stations. For Fremont County it lists a set of towns with an elevation and a load for each. Three of them are in this corridor:
| Station | Elevation | Ground snow load | On this site |
|---|---|---|---|
| Ashton | 5,260 ft | 103 psf | Written up in full |
| Warm River | 5,297 ft | 108 psf | Written up in full |
| Drummond | 5,607 ft | 114 psf | Written up in full |
| Chester | No station in the study | Nothing to write | |
| Marysville | No station in the study | Nothing to write | |
That is not an oversight in the research. A study built on weather-station records can only report places that have a weather station, and most small settlements do not. The authors anticipated the gap and said plainly what should happen in it:
the authority having jurisdiction must approve ground snow loads for sites that are not specifically defined in this report. Ground snow load determination for such sites must be based on an extreme value statistical analysis of data available in the vicinity of the site using a value with a 2 percent annual probability of being exceeded (i.e., 50-year MRI).
— Al Hatailah, Godfrey, Nielsen and Sack, "Ground Snow Loads for Idaho, 2015 Edition", University of Idaho Department of Civil Engineering (lib.uidaho.edu, retrieved 2026-08-17)
Two things follow from that sentence, and both are practical. The authority having jurisdiction — here, Fremont County — is the body that approves the load, not the study and not a supplier. And the proper method for an undefined site is a statistical analysis by someone competent to do it, which is emphatically not an average of the two nearest towns.
The ordinance assigns by district, and never says where the districts are
The county's route to a snow load is different: it does not name towns at all. Ordinance No. 2005-02 sets a ground snow load for each of four named districts. Two of those districts are this corridor's, and this site has written both.
What the ordinance does not do — anywhere in its text — is define where one district ends and the next begins. There is no boundary description, no list of townships and ranges, no schedule of included towns. The boundary exists only on the county's snow load zone map, which is published as an image.
So the two questions a Chester owner needs answered are each unanswerable from the text alone: the study has no station, and the ordinance has no boundary. Those are different gaps, and neither one fills the other.
What that actually means for a build
Less than it sounds, and this is the reassuring half of the page. A snow load is not something an owner determines and hands to a builder. It is determined for the project, by people whose stamp is on it.
- The county assigns the district. The building department works from its own map and tells you which district your parcel is in. That is an answer you can get by telephone, and it is authoritative in a way that no reading of the map by you or by us would be.
- The engineer designs to the assigned load. Once the district is fixed, the ordinance figure is the design input, and the corridor's figures are already published on this site.
- Station data is corroboration, not authority. The University's study says so itself: it is not legally binding, and it urges readers to verify values with the local authority having jurisdiction.
- Interpolating between towns is not a method. Chester sitting geographically between two stations does not entitle anyone to average their loads. Snow load tracks elevation and exposure in ways that a straight line between two dots does not capture.
The one thing not to do
Do not read a figure off the zone map yourself and build to it. The map is an image, its legibility varies with how it is reproduced, and a parcel near a boundary is exactly the case where a confident reading is worth least. A misread district on a corridor lot is a roof designed to the wrong number, and that is not a defect anyone finds until there is snow on it.
The same caution applies in reverse to anything you are told casually. A neighbour's figure is a figure for the neighbour's parcel, which may be in a different district and is certainly at a different elevation and exposure.
| Source of a number | What it is worth |
|---|---|
| The county's written district determination for your parcel | The answer. This is what the design is built on |
| The ordinance figure for that district | The design input, once the district is fixed |
| A nearby station in the University study | Corroboration, expressly not legally binding |
| Your own reading of the image-only zone map | An estimate, and worth least exactly where it matters most |
| A neighbour's figure, or a number in conversation | A different parcel's answer |
| An average of the two nearest towns | Not a method the study recognises |
How to settle it in one afternoon
- Telephone Fremont County Building on (208) 624-7200 with your parcel number and ask which snow load district it is in. Ask for the answer in writing or by email if the parcel is anywhere near a boundary.
- Get the district figure from the ordinance rather than from a supplier, and put it in the project file.
- Give the figure to whoever is designing the structure, and confirm it appears on the stamped drawings. The county permit page covers where stamped plans sit in the process.
- Ask every truss and package supplier to state in writing which ground snow load they designed to. Two quotes naming different loads are not comparable at any price.
- Keep the district determination with the house file permanently. A future buyer's inspector, insurer or engineer will ask, and reconstructing it years later is far harder than saving one email now.
Checked 2026-08-17 against Fremont County Ordinance No. 2005-02 and the University of Idaho's "Ground Snow Loads for Idaho, 2015 Edition", published by the University of Idaho Library. County ordinances are amended and research is re-issued; the county building department is the authority on district assignment.
Common questions
What is the ground snow load at Chester, Idaho?
There is no published figure specific to Chester. The University of Idaho's snow-load study has no station there, and the county ordinance assigns loads by district rather than by town. The county building department determines which district a parcel is in.
What about Marysville?
The same. Marysville has no station in the study, and the ordinance names districts rather than towns. Ask the county which district the parcel falls in.
Which corridor towns does the study cover?
For this corridor it lists Ashton at 5,260 feet and 103 psf, Warm River at 5,297 feet and 108 psf, and Drummond at 5,607 feet and 114 psf. All three are written up on this site.
Why does the ordinance not say where the districts are?
It simply does not contain a boundary description — no townships and ranges, no schedule of towns. The boundary exists on the county's snow load zone map, which is published as an image rather than as text.
Can I just read the zone map myself?
It is not a safe basis for a design. The map is an image, its legibility varies with reproduction, and a parcel near a boundary is exactly where a confident personal reading is worth least. Get the district from the county.
Can I average the loads from the nearest two towns?
No. Interpolating between stations is not a method. Snow load tracks elevation and exposure in ways a straight line between two data points does not capture, which is why the county assigns by district rather than by distance.
Is the University of Idaho figure binding?
No, and the study says so itself. It states that it is not legally binding and urges readers to verify ground snow load values with the local authority having jurisdiction. It is corroboration; the ordinance is the authority.
Who actually decides the number my house is built to?
The county assigns the district, the ordinance supplies the figure for that district, and the engineer designs to it and stamps the drawings. An owner's job is to get the district determination and make sure it reaches the right people.
Can I rely on what a neighbour tells me?
Only as a starting point. A neighbour's figure is for their parcel, which may sit in a different district and certainly has a different elevation and exposure.
What should I keep in the file?
The county's written district determination, the ordinance figure, and every supplier's written statement of the ground snow load they designed to. A future buyer's inspector, insurer or engineer will ask, and it is very hard to reconstruct later.