Deck railing height by code
The railing height codes set is a minimum guard height, measured from the deck surface to the top of the rail:
| Code | Height | When required |
|---|---|---|
| US IRC 2021 R312.1 / 2024 R321.1[1][2] | 36 in (914 mm); 34 in on the open side of a stair | deck more than 30 in above grade within 36 in of the edge |
| US IBC 1015.3[3] | 42 in (1,067 mm) | commercial and multifamily (with dwelling exceptions) |
| England, Approved Doc K[5] | 1,100 mm for external balconies; 900 mm stairs and landings | drop more than 600 mm |
| Canada NBC 9.8.8.3[6] | 900 mm if the deck is 1,800 mm or less above ground; otherwise 1,070 mm | drop more than 600 mm within 1.2 m |
| Australia NCC 11.3.4[7] | 1 m (865 mm on stairs) | fall of 1 m or more |
Openings and balusters
Railing height is only half the rule; the infill must also stop a child. Under the IRC no opening may pass a 4 in sphere (4-3/8 in on the open side of a stair, 6 in at the triangle under the bottom rail)[1]. The UK and Canada use 100 mm and Australia 125 mm. Lay out the balusters with the baluster spacing calculator.
Posts and loads
- Guards and handrails must resist a 200 lb concentrated load at the top in any direction, and infill a 50 lb load[1].
- AWC's prescriptive deck guide uses 4x4 minimum guard posts attached to 2x8 or deeper joists, with hold-downs rated 1,800 lb, for guards up to 36 in high[4].
- Commercial 42 in guards and taller residential guards need their own design.
Planning the railing
The railing length, post count and baluster count come from the deck calculator. Stairs down from the deck need a handrail at 34 to 38 in once they have four or more risers; see the handrail height page and the deck stair calculator.
Local rulesSome cities require taller guards or stricter infill. Check with your building department before you order posts.
Frequently asked questions
How high does a deck railing have to be?
At least 36 in above the deck surface under the IRC, where the deck is more than 30 in above grade. Commercial decks need 42 in.
At what height does a deck need a railing?
When the walking surface is more than 30 in above the ground at any point within 36 in of the edge (IRC).
Is deck railing height measured from the deck boards?
Yes. It is measured vertically from the walking surface to the top of the guard.
What is the railing height in Canada?
900 mm for a deck serving one dwelling when it is 1,800 mm or less above the ground, otherwise 1,070 mm (NBC 9.8.8.3).
Sources
- 2021 International Residential Code, Chapter 3: Building Planning (R301.5, R311.7 stairways, R312 guards)
- 2024 International Residential Code, Chapter 3 (R318.7 stairways, R320 handrails, R321 guards)
- 2021 International Building Code, Chapter 10: Means of Egress (1011.5.2, 1015.3)
- DCA 6: Prescriptive Residential Wood Deck Construction Guide (2015 IRC basis)
- Approved Document K: Protection from falling, collision and impact (2013 edition, for use in England)
- National Building Code of Canada 2020, Division B, Part 9, Section 9.8 Stairs, ramps, handrails and guards
- ABCB Housing Provisions, Part 11.3 Barriers and handrails (NCC 2022)