Building Code Requirements for Decks

Building Code Requirements for Decks


Footings must extend to frost depth (42 inches minimum) and are required for any deck that is attached to a dwelling or garage that has frost footing. Bottom of footing must be belled to 4 inches larger than tube used.


Decks and balconies need to be designed for a 40 pound per square foot live load. Decks exposed to the weather must be constructed of approved wood with natural resistance to decay such as redwood, cedar or treated wood.

Also members which form the structural support including: horizontal members such as beams, joists, ledger boards and decking; and vertical members such as posts, poles, and columns need to be so constructed. Ledger boards must be bolted or lagged to the building and all connections between the deck and dwelling must be flashed. Decks shall be positively anchored to primary structure and designed for both vertical and lateral loads.

Proper hardware (nails, hangars, brackets etc.) must be compatible with the type of treated lumber. Before using alternative building products, check with one of the building inspectors, some plastic / composite decking materials have not been tested and approved for use.

Columns & Posts

Columns and posts in contact with the ground or embedded in concrete, earth or masonry must be of special pressure treated wood approved for ground contact (.40 treated).


Deck joist should not overhang beams by more than 2 feet, nor should beams overhang posts by more than a foot at the ends. Floor joist spacing at 24 inches on center requires 2x decking minimum and floor joist spacing at 16 inches on center requires 5/4" decking minimum. Cedar or redwood posts need proper separation from ground.

Open Sides

All decks, balconies or porches, open sides of landings and stairs which are more than 30 inches above grade or a floor below must be protected by a guard not less than 36 inches in height. Open guard and stair railings require intermediate rails of an ornamental pattern such that a sphere 4 inches in diameter cannot pass through, and must withstand a horizontal force of 50# per square foot.


If a stairway is to be provided, it must be not less than 36 inches in width. Stairways may be constructed having an 7 3/4 inch maximum rise (height) and a 10 inch minimum run (length). The largest treat rise and treat run may not exceed the smallest corresponding tread rise or run by more than 3 / 8 inch. Stairway illumination is required by the code. Stair treads must be nominal 2 inches thick. No openings in risers greater than 4 inches.


Handrails are required on all stairways having 4 or more risers. Handrails may not be less than 1 ¼ " nor more than 2" in cross sectional area (diameter). Handrails must be installed not less than 34 inches nor more than 38 inches above the nosing (front edge) of treads, be continuous, and be returned at the ends or terminate at a post.


The electrical code may require overhead power lines to be located a minimum 10 feet above decks and platforms (check with the State Board of Electricity at 651-642-0800).


When locating a deck care must be given to the location of existing gas and electric meters, wells, and septic systems. Prior to the placement of any deck that will interfere with these devices, contact 1 of the building inspectors.

Additional Information

Gopher State One Call. Call at least 2 full business days before you dig. 651-454-0002 or 1-800-252-1156. Visit the Gopher State One Call Website for more information.

Note: For specific code requirements, please contact the Chisago County Building Department.

Special Design Note: Some deck designs may not be appropriate should the placement of a screen porch or 3 season porch on (or underneath) the deck platform be a future consideration.


For questions regarding a permit please call 651-213-8370.

For code questions please call Justin Colberg at 651-213-8370.