Billings Deck Guide: Permits, Frost, Snow, Hail (2026)

Updated October 25, 2026. This guide is general information, not legal or engineering advice. Rules change, so confirm with the agency listed before you start work.

Quick reference

Topic	What to know	Source
Frost depth	42 inches	City of Billings design criteria
Roof snow load	30 psf minimum; 33 psf for drift and unbalanced loads	City of Billings design criteria
Design wind speed	110 mph for residential	City of Billings design criteria
Residential code	2021 International Residential Code	City of Billings
Permits in the city	Decks need a building permit; apply online	City of Billings FAQs
Outside city limits	City issues no permits; county zoning may apply	City of Billings; Yellowstone County Planning
Contractors	No trade license; contractors with employees register with DLI	Montana DLI

How deep should deck footings be?

The City of Billings publishes design criteria for builders, and they list a 42-inch frost depth for foundations. Deck footings need to reach that depth so freezing soil can't lift them. Posts set on surface blocks or footings that stop short are a common reason older decks tilt, sag or pull away from the house. Outside city limits, ask the builder what depth they're designing to; using the same 42 inches is a sensible starting point.

Do I need a permit?

Inside Billings city limits, yes. The city's FAQs say a building permit is required for almost any construction on private property and list decks by name. Billings uses the 2021 International Residential Code for one- and two-family homes, and permit applications go through the city's online permit portal, so only one set of plans is needed. The city also says the owner is responsible for getting permits but may designate the contractor to do it, and that the owner should make sure the contractor got the permits and passed inspections.

What if I'm outside city limits?

Since October 1, 2003, the City of Billings has not issued building, plumbing, mechanical or electrical permits outside its city limits. The state's Building Codes Bureau says that outside cities certified to issue their own permits, state law exempts residential buildings with fewer than five dwelling units from a state building permit. County rules can still apply. The Yellowstone County Planning Division issues county zoning compliance permits for properties outside Billings that fall within the county's zoning jurisdiction, and the site plan for that permit has to show existing and proposed structures, including decks and porches. Other towns, such as Laurel, have their own building departments.

Who can build a deck in Montana?

Montana doesn't have a trade license for deck builders. The Department of Labor and Industry says all construction contractors with employees must register, and it defines a construction contractor as anyone who adds to or takes away from an improvement attached to real estate. Registration costs a $70 application fee and isn't a test of skill. The department suggests asking a contractor for proof of registration and checking that it's in good standing through its website.

What does the climate do to decks?

Downtown Billings has a cold semi-arid climate. Billings Logan International Airport, which sits on top of the Rims, averages about 14.31 inches of precipitation and 57.4 inches of snow a year, with records of 111°F and −38°F. Chinook winds pass through in winter, so snow often melts off rather than piling up. For a deck, that means plenty of freeze-thaw cycles and long stretches of strong, dry sun, which crack wood and wear out stain.

What snow and wind loads matter?

An open deck has to carry people and furniture; a deck roof also has to carry snow and resist wind. The city's design criteria set a 30 psf minimum roof snow load after allowed reductions, with 33 psf used for drift and unbalanced loads, and a 110 mph design wind speed for residential buildings. Expect a covered deck to need larger posts and footings than an open one.

How bad is the hail?

Hail and severe wind are part of summer in Yellowstone County. During a stretch of storms from June 13 to 16, 2025, the National Weather Service in Billings issued 96 severe thunderstorm warnings. On June 16, hail around 1.5 inches and gusts up to 76 mph hit the Billings Heights, Shepherd and Worden, stripping roofs and siding, and wind-driven hail heavily damaged homes in Shepherd and Huntley. In 2010, a tornado struck downtown and the Heights with hail up to golf-ball size. If a storm damages your deck, photograph it and contact your insurer before repairs begin.

Questions to ask a builder

Are you registered with the Montana Department of Labor and Industry, and are you insured?
Who will pull the permit, and which inspections will there be?
How deep will the footings go, and how will the ledger be fastened and flashed?
Which decking and railing hold up best to sun and hail on my lot?
What does your workmanship warranty cover, and what do the manufacturers cover?

Common questions

Do I need a permit to build a deck in Billings?

Yes, inside city limits. The City of Billings lists decks among projects that need a building permit. Outside the city, check with Yellowstone County Planning or your town.

Does Montana license deck builders?

No trade license exists. Construction contractors with employees must register with the Montana Department of Labor and Industry.

How deep do deck footings need to be in Billings?

The City of Billings design criteria list a 42-inch frost depth.

Billings deck guide (2026)