Deck Railing and Stair Code in Fort Collins CO

Deck Railing and Stair Code in Fort Collins

Fort Collins requires a deck guard wherever the deck is 30 inches or more above grade, measured 3 feet out from the edge, with openings under 4 inches and cable railing at 3 inch spacing. Stairs need risers of 4 to 7-3/4 inches, treads of at least 10 inches, a handrail at 4 risers, landings at both ends and a light at the top. This guide collects every railing and stair rule from the City's 2026 deck guide and the county handout.

Last reviewed November 2026.

Deck railing and stair code in Fort Collins, in one table

Guard, handrail and stair rules for Fort Collins decks

Item	Rule
Guard required	Deck 30 in or more above grade, measured 3 ft out from the edge
Guard height	36 in minimum (Larimer County)
Guard openings	Under 4 in at the deck; under 4-3/8 in on stairs
Cable railing	3 in max cable spacing; posts 4 ft on center max
Guard posts	Fastened into joists, beams or blocking, never into end grain (details below)
Handrail	4 or more risers: graspable, at least one side
Handrail height	34 to 38 in above nosings, continuous, returned at the ends (Larimer County)
Stair width	36 in minimum
Risers	4 in to 7-3/4 in; open risers under 4 in
Treads	10 in minimum; composite treads at the maker's stringer spacing
Long stairs	Center support past 6 ft
Stair attachment	To a beam or double joist with metal connectors; not hung below; no toenails
Landings	Solid and level, 36 x 36 in minimum, top and bottom
Stair light	Wet-listed light at the top landing; new fixtures shielded and aimed down (local amendment)

Rows are Fort Collins rules from the Residential Deck Guide (revised June 24, 2026), written to the 2024 IRC (guard posts R507.10, handrails R320, landings R318.7.6), unless marked Larimer County; those come from the county's Residential Deck Information handout, which applies outside city limits.

Guards: when and how

The trigger is measured, not guessed: 30 inches or more above grade at a point 3 feet out from the deck edge. On a sloping yard that point can be lower than the ground right at the deck, so a deck that is 24 inches up at the house can need a guard at the far side. Openings stay under 4 inches; along a stair, under 4-3/8 inches.

Post attachment

The 2024 code is specific about how guard posts hold. Posts mounted on top of the deck connect to the joists, beams or blocking below. Posts mounted on the side of a beam or joist connect to the adjacent joist so they can't rotate outward, and nothing fastens into end grain. That is the detail older decks most often fail, and the reason deck railing replacements in Fort Collins are permitted work.

Cable

Cable flexes, so the City sets a 3 inch maximum spacing and 4 foot maximum post spacing. The cable railing page covers the build.

Raised gray composite deck with black aluminum railings and lattice skirting behind a brick house — Gray composite decking with black aluminum railings and lattice skirting.

Stairs and landings

At least 36 inches wide.
Attached to a beam or a double joist with metal connectors: lag screws, bolts or approved hangers, never toenails or nails that can pull out, and never hung below the beam or joists.
Center support on any stair longer than 6 feet.
Risers 4 inches minimum, 7-3/4 inches maximum; open risers keep openings under 4 inches.
Treads at least 10 inches deep; composite treads follow the maker's stringer spacing.
A solid, level landing at top and bottom, at least 36 by 36 inches.
A graspable handrail on at least one side once there are 4 or more risers.
A wet-listed light at the top landing; new fixtures shielded and aimed down.

Long stairs are where these add up, so a second story deck is planned around its stair from the start. Larimer County's version, with nosing and variation limits, is in the Larimer County deck permit guide.

Stained wood deck with railings and stairs looking over a backyard in autumn — A stained wood deck and stair railing in autumn.

Under the deck: egress windows

If a deck goes over the window well of a basement escape window, Fort Collins requires 36 inches of clear height from the top of the well to the underside of the deck structure, so the window still works as a way out.

Deck Railing and Stair Code: Questions

Covered deck with horizontal cable railings, a dining table and a view of sunlit forest

Horizontal cable railings on a covered deck, the view left open.

What is the deck railing height code in Fort Collins?

A guard is required wherever the deck is 30 inches or more above grade, measured at a point 3 feet out from the deck edge, per the Fort Collins Residential Deck Guide. Larimer County's deck handout sets that guard at 36 inches minimum. Openings in the guard must be under 4 inches at the deck and under 4-3/8 inches on stairs.

How far apart can deck balusters be?

Close enough that a 4 inch sphere can't pass: openings less than 4 inches on the deck and less than 4-3/8 inches along stairs in Fort Collins. Cable railing is tighter, with cables no more than 3 inches apart and posts no more than 4 feet on center.

When do deck stairs need a handrail?

When a flight has 4 or more risers, landing to landing, Fort Collins requires a graspable handrail on at least one side. Larimer County's handout words it as more than three risers, with the rail continuous, 34 to 38 inches above the tread nosings, and returned to posts at the ends.

What are the stair rise and run rules for a deck?

Risers from 4 inches to 7-3/4 inches and treads at least 10 inches deep in Fort Collins, with open risers keeping openings under 4 inches. Larimer County adds a 3/4 to 1-1/4 inch nosing, an 11 inch tread if there's no nosing, and no more than 3/8 inch variation across a flight.

Do deck stairs need a landing?

Yes. Fort Collins requires a solid, level landing, such as flagstone or concrete, at the top and bottom of exterior deck stairs, at least 36 inches deep in the direction of travel and 36 inches wide or the width of the stair.

Do deck stairs need a light?

Yes. Fort Collins requires a wet-listed exterior light at the top landing to light the stairs, and under a local amendment a new fixture must be shielded and aimed down, dark-sky compliant.