Type your deck's size and how high it is, and whether it is attached to the house. You get whether it needs a permit under the model building code most US cities start from, with the code's own words, and what the inspector checks. Your city adopts the code with its own changes, so its building department has the last word.
Does your deck need a permit?
Permit needed: attached to the house192 sq ft, 24″ high, attached · IRC 2021 R105.2 · your city may set its own line
What the inspector checks
Quick answer: under the model building code most US cities start from (the International Residential Code, IRC 2021), a deck needs no permit only when all four are true: it is 200 square feet or smaller, no more than 30 inches above the ground at any point, not attached to the house, and no door of the house opens onto it. Any attached deck, any deck over 200 square feet or higher than 30 inches needs one. A hot tub’s new circuit needs an electrical permit either way. Your city adopts the code with its own changes, so its building department has the last word.
How to use the deck permit checker
- Type the deck’s length and width (feet, or meters with the toggle) and how high its floor is above the ground at its highest point: on a slope, measure at the low end of the ground.
- Attached or free-standing? A deck fastened to the house with a ledger board is attached, even when posts carry the other side.
- A door onto it, a roof, a hot tub: each changes the answer, and the checker shows the code’s own words for each.
- Read what the inspector checks: the code’s deck rules that apply to your deck, permit or not. Add your city to get a link to its building department. Copy link keeps your deck (never your city).
The code’s rule: four lines, all of them
The IRC’s list of work that needs no permit (R105.2) includes, word for word: “Decks not exceeding 200 square feet (18.58 m2) in area, that are not more than 30 inches (762 mm) above grade at any point, are not attached to a dwelling and do not serve the exit door required by Section R311.4.” Miss one line and the deck is not on the list.
| The deck | Permit under the model code? | Why |
|---|---|---|
| 12 × 12 ft, 18″ high, free-standing | No | 144 sq ft, under 30″, not attached |
| 10 × 20 ft, 24″ high, free-standing | No | exactly 200 sq ft is “not exceeding” 200 |
| 12 × 20 ft, 24″ high, free-standing | Yes | 240 sq ft is over 200 |
| 12 × 12 ft, 36″ high, free-standing | Yes | over 30″ above the ground |
| 10 × 10 ft, 12″ high, attached | Yes | attached to the house, however small |
A roof, a hot tub, a door
A door. A deck that a house door opens onto serves the house’s exit door, and the exemption leaves out any deck that does.
A roof. The deck exemption says nothing about a roof. On an attached deck, a roof is on no list of exempt work. Over a free-standing deck of 200 square feet or less, the roofed deck may count as a small detached building, which R105.2 also exempts: “Other than storm shelters, one-story detached accessory structures, provided that the floor area does not exceed 200 square feet (18.58 m2).” Whether your covered deck is one is your building department’s call.
A hot tub. Two things. Its wiring falls under the code’s chapter on pools, spas and hot tubs, “whether permanently installed or storable” (E4201.1), and a new circuit is electrical work that needs a permit (R105.1). And its weight: the IRC’s deck tables build for 40 pounds per square foot (Table R301.5); water weighs 62.4 pounds per cubic foot, so 8 inches of it is already 41.6 psf. A deck under a hot tub has to be designed for it (R507.1 sends “conditions not prescribed in this section” to R301), which usually means an engineer.
What the inspector checks
- Footings: concrete, at least 12 inches below the undisturbed ground (R507.3.2), and below the frost line when the deck is attached to the house (R507.3.3). A free-standing deck of 200 square feet or less whose joists sit on precast pier blocks, no more than 20 inches high near its edges, needs none (R507.3, Exception 2).
- The ledger and the attachment: at least a 2×8 ledger, “shall not be supported on stone or masonry veneer” (R507.9.1.1), anchored for vertical and sideways loads and never “by the use of toenails or nails subject to withdrawal” (R507.8), with hold-downs near each end (R507.9.2).
- Guards: where the floor is more than 30 inches above the ground within 36 inches of the edge (R312.1.1), at least 36 inches high (R312.1.2). The free railing height and baluster spacing calculator lays yours out.
An exempt deck is not exempt from the code: “Exemption from permit requirements of this code shall not be deemed to grant authorization for any work to be done in any manner in violation of the provisions of this code or any other laws or ordinances of this jurisdiction.”
Common mistakes
- Measuring the height at the house. The line is “above grade at any point”: on a sloping yard, the highest point may be the far corner.
- Calling a deck free-standing because it has posts. One ledger on the house makes it attached.
- Forgetting the door. A low deck outside a door is not on the exempt list.
- Building to the size line, then adding a hot tub. The tub’s wiring needs a permit, and the deck has to be designed for its weight.
- Trusting the model code alone. Your city may change the size or height line, or ask for a permit for every deck. Check before you buy lumber.
Deck permits: questions people ask
Do you need a permit to build a deck?
Under the IRC 2021, yes, unless all four are true: 200 square feet or smaller, no more than 30 inches above the ground at any point, not attached to the house, and not serving a house door (R105.2). Your city may set a stricter line.
What size deck can I build without a permit?
Up to 200 square feet (a 10 × 20 or 14 × 14 foot deck), free-standing, no more than 30 inches high and with no house door onto it, under the model code. Check your city’s own line.
How high can a deck be without a permit?
30 inches above the ground at any point, under the IRC’s exemption, and the same 30 inches is where guards become required (R312.1.1).
Do I need a permit for a freestanding deck?
Not under the model code if it is 200 square feet or smaller, no more than 30 inches high and no house door opens onto it. Bigger or higher, yes.
What are the deck permit requirements?
The deck must follow the IRC’s deck section (R507): footings at least 12 inches deep and below the frost line when attached, a ledger of at least a 2×8 on the house’s band joist (never on stone or brick veneer), hold-downs, and guards at least 36 inches high where the floor is more than 30 inches up.
How much does a deck permit cost?
Each city sets its own fee schedule; the code’s permit application asks you to “State the valuation of the proposed work”. Your building department’s fee schedule has the number.
Read next
- Low deck ideas at ground level
- Deck railing designs
- DIY pallet patio deck designs
- Small deck furniture layouts
Remodeling inside too? The free remodel permit checker answers the same question for every job in the house, and the 2D planner lays out the deck’s furniture.
Source, read October 15, 2026: the International Residential Code 2021 — R105.1, R105.2, R301.5, R311.5, R312.1.1–2, R507.1–R507.9.2, E4201.1 and E4208.1 — as published by UpCodes for Colorado’s DFPC Residential Code 2021, which adopts it without amendments. Your city’s code may differ: this page is not legal advice, and it is re-checked every six months.