In the fall of 2022 a county engineer in northern Minnesota called us about replacing the overhead doors on a salt storage facility their road maintenance department had been running since 1998. The original doors were a generic commercial product with galvanized hardware. After 24 winters of plowing operations and end-of-shift truck washdowns, the hardware had been replaced piece by piece for years and the panels were starting to flag.
The project ended up being a typical DOT door replacement, and it walks through most of the design decisions that come up on similar facilities. This post uses it as a case study.
The site
The facility had three overhead door openings:
- Two on the salt storage building, both 20 feet wide by 14 feet tall to accommodate front-end loaders and tandem plow trucks
- One on the adjacent washdown bay, 14 feet wide by 12 feet tall, where trucks were rinsed at the end of a shift before going back into storage
The salt shed openings faced the prevailing wind off a nearby lake, which meant salt-laden atmosphere migration into the building was constant from October through April. The washdown bay added high-pressure hot water exposure on top of that.
The original spec problem
The original 1998 doors were rated commercial-grade but the hardware package was galvanized throughout. By 2010 the rollers were already being replaced annually. By 2018 the bottom rails on the salt shed doors had rusted through enough that fasteners were pulling free of the panel. The maintenance team had been making it work, but the road back to a fully functional system was a full replacement.
This is the pattern we see most often at DOT facilities: the original spec was not wrong for normal commercial use, but it was wrong for a salt environment. Galvanized hardware in a salt shed has a service life of two to four years. The buildings outlast that hardware by a factor of five or six.
What went in
For the two salt storage openings, we shipped Goliath polycarbonate doors sized at the full 20-foot width. The translucent polycarbonate panel transmits enough daylight that interior lighting load dropped meaningfully, and the panel itself is essentially immune to the salt chemistry.
For the washdown bay, a Survivor polycarbonate door at standard wash bay sizing. The panel handles the chemistry the same way and the standard size shipped faster than the oversized Goliath builds.
All three doors were specified with:
- 316 stainless steel hardware throughout. Track, hinges, bearing plates, brackets, fasteners. The 316 alloy specifically because of the chloride exposure profile of a salt environment
- Magnum stainless rollers. Standard steel rollers seize within a season at facilities like this
- Heavy bottom rail specification on the Goliath doors. The salt floor of the shed wears the rail constantly, and the heavier rail extends life
- Supralift II air-powered operators on all three openings. The existing facility had compressed air for other shop equipment, and the operator family has the longest track record in DOT washdown applications we ship to
Total lead time was five weeks from order to delivery, which fit the off-season install window the county was working in.
What we learned on this install
A few things came up during the install that apply to similar projects:
- Headroom was tighter than the original drawings showed. Once we field-measured, we found 14 inches of headroom on the salt shed openings instead of the 18 inches the building plans indicated. We shipped a low-headroom track kit on both openings. Lesson: always field-verify headroom on existing buildings before the order is finalized
- The original cable drums were sized for a lighter panel. The Goliath panels are heavier than the original doors had been, so the counterbalance package had to be re-sized as part of the package. Standard for replacement projects in oversized openings
- Air supply quality on the existing compressed air system was marginal. We added an inline air dryer on the supply to the operators. Without it, condensate in the lines would have shortened the operator service life materially
What other DOT and salt facility operators should take from this
The patterns that apply nearly universally to salt shed and DOT washdown projects:
- 316 stainless is the right alloy for salt environments. 304 stainless is acceptable for many wash applications. For active salt exposure, 316 is the spec
- Polycarbonate panels solve the panel-side corrosion question. They do not rust, do not pit, and do not weaken under chloride exposure
- Oversized openings need engineered counterbalance. Generic spring drum packages are sized for typical commercial openings, not 20-foot DOT doors
- Air-powered operators have a track record in this application. Supralift and NuMax are both engineered for the exposure
For state DOT projects working under a published specification, the Federal Highway Administration’s salt storage guidance is a useful reference for building design considerations. Most state DOTs publish their own door specifications as part of their standard plans, and our team works directly with engineers and contractors on these projects.
Get a DOT-spec quote
If you are working on a salt shed, a washdown bay, or any state DOT facility door project, share the project details with us. Our team will review the specification, return a compliant product recommendation, and walk through the lead time and any approval documentation the project requires. We carry the certifications most state DOT specs reference and we keep replacement parts for these doors in inventory at the Bemidji warehouse.