Spot the Violation

FramingMinnesota building permits & inspectionsLevel 22018 IRC

Backyard platform on deck blocks

Back yard of a one-story house in summer. A small square freestanding platform deck of pressure-treated lumber sits on the lawn several feet away from the house wall, resting on precast concrete deck blocks, with three wide steps down to the grass and no railing. A tape measure held at the deck edge reads 18 in. to the grass. Two patio chairs and a potted plant sit on the deck. 18"
Backyard platform, finished this spring

In a city that enforces the State Building Code, the owner built this 10 x 12 ft freestanding platform. It is 18 in. above the lawn, sits on precast deck blocks, and stands clear of the house with no ledger or other connection. It is not part of an accessible route. No building permit was pulled. What's wrong here?

  1. Nothing. This installation is compliant
  2. Every deck in Minnesota needs a building permit, whatever its height or size
  3. A deck this high must have a 36 in. guard around its open sides
  4. It needs a permit because it is over 100 sq. ft.
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Show the answer and the code reference

The answer

Nothing is wrong. A freestanding platform 30 in. or less above grade, not attached to the house and not on an accessible route, is exempt from a building permit in Minnesota.

Correct choice: 1. Nothing. This installation is compliant

Minn. Rules 1300.0120, subp. 1 makes a permit the default for construction, but subpart 4 lists work exempt from permit. That list includes decks and platforms not more than 30 in. above adjacent grade, not attached to a structure with frost footings, and not part of an accessible route. This platform is 18 in. up, freestanding with no ledger, and not on an accessible route, so no building permit is required. The exemption covers the permit only. The platform still has to meet the code, and at 18 in. that does not include a guard, which starts above 30 in. (IRC R312.1.1). The city's zoning rules on setbacks or lot coverage are a separate question.

How to fix it

No correction needed. If the owner later attaches it to the house, raises it above 30 in., or makes it part of an accessible route, it will need a building permit.

Code references

  • Minn. Rules 1300.0120, subp. 4 — Permits: work exempt from permit

    Exempt from a building permit: decks and platforms not more than 30 inches above adjacent grade, not attached to a structure with frost footings, and not part of an accessible route. An exemption does not authorize work in violation of the code or of other laws or ordinances.

    Drills citing 1300.0120, subp. 4

  • Minn. Rules 1300.0120, subp. 1 — Permits: required

    An owner or authorized agent who intends to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure must first get the required permit from the building official, unless the work is exempt.

    Drills citing 1300.0120, subp. 1

  • IRC 2018 R312.1.1 — Guards: where required

    Guards are required along open-sided walking surfaces, including stairs, ramps, and landings, that are more than 30 inches measured vertically to the floor or grade below at any point within 36 inches horizontally to the edge of the open side. A deck surface is an open-sided walking surface.

    Drills citing R312.1.1

Minnesota

Minnesota ruleConfidence: medium

The permit question is State Building Code administration (Minn. Rules ch. 1300), which replaces IRC chapter 1 in Minnesota. Minnesota's deck exemption differs from the model IRC's R105.2. The construction rules (guards, footings, framing) come from the Minnesota Residential Code (Minn. Rules ch. 1309, the 2018 IRC with Minnesota amendments). DLI has begun rulemaking toward the 2024 IRC, with no effective date yet.

About the Minnesota Residential Code

Citation under review. Audited 2026-10-04. The subpart 4 deck exemption wording, including 'not attached to a structure with frost footings', was re-confirmed through search results quoting Minn. Rules 1300.0120 and city deck handouts (revisor.mn.gov could not be fetched). No source showed an area limit on it. IRC 2018 R312.1.1 is cited from memory of the model code; the earlier summary's 'including decks' was replaced with the model code's 'stairs, ramps, and landings'. Whether Minnesota amends R312.1.1 in ch. 1309 was not checked.

Why the other choices are wrong

  • Every deck in Minnesota needs a building permit, whatever its height or size. Minn. Rules 1300.0120, subp. 4 exempts decks and platforms not more than 30 in. above adjacent grade that are not attached to a structure with frost footings and are not part of an accessible route. This platform meets all three conditions.
  • A deck this high must have a 36 in. guard around its open sides. Guards are required on open sides of walking surfaces more than 30 in. above the floor or grade below (IRC R312.1.1). This platform is 18 in. up.
  • It needs a permit because it is over 100 sq. ft. Minnesota's deck exemption turns on height, attachment, and accessible route, not area. At 120 sq. ft. it would also fit under the model IRC's 200 sq. ft. figure, which Minnesota does not use for decks anyway.
Code complianceLevel 2 · Journeyman#minnesota#permit#permit-exemption#deck#compliant

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