Larimer County Deck Guide: Permits, Frost Depth & Soils (2026)

Updated October 29, 2026. This is general information, not legal or engineering advice. Each town sets its own rules and they change, so confirm with the building department for your address.

Quick reference

Topic	Rule or fact	Source
Fort Collins footings	30 in. minimum for attached decks; 12 in. for freestanding	City of Fort Collins deck guide
County footings	30 in. minimum frost depth unless solid rock	Larimer County deck handout
Fort Collins permit triggers	Attached, over 30 in., over 200 sq ft, front-door landing, most structural repairs	City of Fort Collins deck guide
Loveland exemption	Under 200 sq ft, under 30 in., freestanding, not main entry	City of Loveland FAQ
Snow load	County: 40 psf at 5,500 ft or less; Windsor and Wellington: 30 psf	Larimer County; Windsor; Wellington
Contractors	City license in Fort Collins; county license in unincorporated Larimer County	City of Fort Collins; Larimer County
Soils	Expansive soil is Colorado's most significant geologic hazard	Colorado Geological Survey
Digging	Contact Colorado 811 at least two full business days ahead	Colorado 811

How deep do deck footings go?

In Fort Collins, the city's residential deck guide sets a minimum footing depth of 30 inches below grade for decks attached to the house and 12 inches for freestanding decks. Diamond piers are allowed with the manufacturer's specifications, but the city requires engineering for diamond piers on second-story decks or decks more than 10 feet to the top of the beam. Larimer County's deck handout for unincorporated areas lists a 30-inch minimum frost depth unless solid rock is encountered; where rock is shallower, it calls for #4 rebar doweled into the rock and epoxied, or an engineered design. Windsor and Wellington each list a 30-inch frost line depth in their design tables.

When is a permit required?

City of Fort Collins. The deck guide requires a permit for any deck or landing serving the front door, any deck more than 30 inches above grade at any point, any deck attached to the house, any deck over 200 square feet, replacing joists, posts, beams or stairs, replacing guard railing, and replacing decking with a heavier material. Engineered plans or letters are required for multi-story or stacked decks, beams hung in hangers, ledgers on cantilevers, decks supporting a hot tub or pool, pergolas or patio covers bearing on a deck, floating stairs, specialty piers, and steel decks that don't conform to code section R505 or are west of Overland Trail.

City of Loveland. Loveland's permit FAQ says a deck needs a permit unless it is under 200 square feet, less than 30 inches above grade, not attached to the house, and not the main entry.

Unincorporated Larimer County. The county's deck handout requires a permit when a deck is more than 30 inches above grade or serves as the main entry or exit, and notes that setback, floodplain and land use rules apply even when no permit is needed.

Windsor, Timnath and Wellington run their own building departments. Windsor lists the 2018 IRC with local amendments as its adopted code.

Guards and stairs in Fort Collins

Guards where the deck is 30 inches or more above grade, measured 3 feet from the edge
Openings under 4 inches on the deck and under 4⅜ inches on stairs
Cable rail: 3-inch maximum spacing, posts at 4 feet on center or less
Stairs at least 3 feet wide, risers 4 to 7¾ inches, treads at least 10 inches
Handrail on at least one side at 4 or more risers; 36 by 36 inch landings top and bottom
36 inches of clearance between a window well and the underside of a deck
A wet-listed light at the top landing, shielded and downward-facing or dark-sky compliant

Inspections

Fort Collins lists five inspection stages for decks: setbacks and footings with pier holes open before concrete, foundation and post connections, rough framing before decking goes on (more than one if concealed connectors are used), rough electrical if any, and final.

Snow, wind and bracing

Larimer County's deck handout ties ground snow load to elevation: 40 psf at 5,500 feet or less, 50 psf from 5,501 to 6,500, 60 psf from 6,501 to 7,000, and 70 psf from 7,001 to 8,000 feet, with engineering required above 8,000 feet. It requires X-bracing on attached decks surfaced 10 feet or more above grade and detached decks 5 feet or more above grade, and engineering for multi-span decks. Windsor's design criteria list 30 psf and a 115 mph design wind speed; Wellington's list 30 psf.

What about expansive soil?

The Colorado Geological Survey calls expansive soil Colorado's most significant geologic hazard and says it causes more property damage than any other natural hazard. Clay-rich soils and soft bedrock containing bentonite can increase in volume by 10 percent or more when wet. The survey names cracked and heaved patios, sidewalks and slabs as common signs, and lists poor drainage, ponding near foundations and irrigation water reaching foundations as causes. Fort Collins' pier chart assumes 1,500 psf soil bearing, and Larimer County requires a design professional's justification to assume more than that on the Front Range.

Who can do the work?

Colorado has no statewide general contractor license, but local ones apply. The City of Fort Collins requires all contractors working in the city to hold a city contractor license, and its deck guide lists classes A, B, C, C2, D, D2 and MM (MM doesn't cover two-story decks); owners working on their own single-family home can apply with a homeowner affidavit. Larimer County has required building contractors in unincorporated areas to hold a county license since September 1, 2009, with a Special class that covers decks, and exempts homeowners working on their own property. Ask any contractor which license covers your address and who will pull the permit.

Wildfire

The Cameron Peak fire started August 13, 2020, burned 208,663 acres in Larimer and Jackson counties, destroyed 469 structures and became the largest wildfire in Colorado history. For decks near grass and timber, NFPA's Firewise guidance notes that wood and wood-plastic composite decking are combustible, that embers collect in board gaps, and that the area under a deck should be kept free of anything that burns.

Before you dig

Colorado 811 says state law requires contacting it at least two full business days before digging, and suggests waiting three. Utility owners mark public lines with paint or flags; private lines such as sprinkler, gas grill or outbuilding lines aren't marked by the service.

Questions to ask a contractor

Which license do you hold for this town, and can I see proof of insurance?
How deep will the piers go, and what soil are you assuming?
Does my design need engineering (hot tub, pergola on the deck, tall diamond piers)?
Who pulls the permit, and which inspections are on the schedule?
What does your workmanship warranty cover, and what does the material warranty cover?

Common questions

How deep do deck footings have to be in Fort Collins?

At least 30 inches below grade for decks attached to the house and at least 12 inches for freestanding decks, according to the city deck guide.

Is a permit required to replace deck boards in Fort Collins?

Only if the new decking is heavier than the old, according to the city deck guide. Replacing joists, posts, beams, stairs or railings does require a permit.

Does Larimer County require a contractor license for decks?

Yes, in unincorporated areas. Since 2009 the county has required building contractors to hold a county license, with a Special class covering decks. Homeowners working on their own property are exempt.

Larimer County deck guide (2026)