The lumber is stacked in the driveway and your brother-in-law is halfway through a story about the deck he built in one weekend with no permit and no trouble. He may well be right about his deck. The question is whether yours is the same deck — and the difference usually comes down to a single detail neither of you has thought about: whether the back door opens onto it.
The short answer: California's residential code lists decks among the work that needs no building permit, but only when all four of these are true — the deck is not more than 200 square feet, is not more than 30 inches above grade at any point, is not attached to a dwelling or townhouse, and does not serve the exit door required by the code (§ R105.2). Miss any one, and you need a permit.
Key numbers
| Condition | Threshold | Where it comes from |
|---|---|---|
| Deck area | Not exceeding 200 square feet | § R105.2 |
| Height above grade | Not more than 30 inches at any point | § R105.2 |
| Attachment | Not attached to a dwelling or townhouse | § R105.2 |
| Egress | Does not serve the required exit door | § R105.2 |
| Detached accessory structure (shed, gazebo) | Floor area not exceeding 120 square feet, one story | § R105.2 |
| Certificate of occupancy | Not required for permit-exempt work | § R110.1 |
The four conditions, one at a time
The exemption reads:
Decks not exceeding 200 square feet in area, that are not more than 30 inches above grade at any point…
200 square feet is not a large deck — 10 by 20, or 14 by 14. It is a patio-sized platform, not an outdoor room.
30 inches above grade at any point is the phrase that quietly disqualifies hillside projects. A deck that is 12 inches up at the house wall and 40 inches up at the downhill corner has a point above 30 inches, so the whole deck fails the test. The same threshold shows up again in the guard rules, which is not a coincidence: 30 inches is where California decides a fall becomes dangerous, and a deck that needs a guard is a deck the building department wants to see.
Not attached to a dwelling or townhouse means freestanding, on its own posts. This is the condition most decks fail. A ledger board bolted to the house is a structural connection to the building, and a badly flashed or badly fastened ledger is the single most common cause of deck collapses — which is exactly why attaching to the house takes the project out of the exemption.
Does not serve the exit door. Your house is required to have an exit door, and the landing or deck outside it is part of getting out in an emergency. A deck that sits under that door is doing a life-safety job, so it is never exempt, however small or low it is.
What "exempt" does not mean
An exempt deck is still governed by the code. The first sentence of the exemption list is the one to remember: exemption from permit requirements shall not be deemed to grant authorization for any work to be done in violation of this code, or of any other law or ordinance of the jurisdiction (§ R105.2).
In practice, three things still apply to a permit-free deck:
- Zoning still applies. Setbacks from your property lines, lot coverage limits, and rules about how much of the yard you may build on are planning rules, not building-permit rules. Skipping the permit does not skip them.
- Structural requirements still apply. Footings, joist spans, ledger connections and composite decking all have code requirements whether or not anyone inspects the work.
- Selling the house still exposes it. An unpermitted structure shows up in disclosures and inspections, and legalizing it afterwards costs far more than permitting it up front.
There is one piece of paperwork you can skip: a certificate of occupancy is not required for work exempt from permits under the exemption list, and is not required for accessory buildings or structures (§ R110.1).
The rest of the backyard list
The same section exempts several other projects homeowners take on in the same weekend:
- One-story detached accessory structures with a floor area not exceeding 120 square feet — the shed and small-gazebo rule. Note the code's own warning attached to this item: these structures may still be regulated by California's Wildland-Urban Interface code despite being exempt from permits, which matters in fire-hazard severity zones.
- Fences not over 7 feet high.
- Retaining walls not over 4 feet in height, measured from the bottom of the footing to the top of the wall, unless they are supporting a surcharge.
- Sidewalks and driveways.
- Prefabricated swimming pools that are less than 24 inches deep.
- Swings and other playground equipment.
- Window awnings supported by an exterior wall that do not project more than 54 inches from the wall and need no additional support.
- Painting, papering, tiling, carpeting, cabinets, countertops and similar finish work.
Two administrative rules sit underneath all of this. Where equipment replacements or repairs have to happen in an emergency, the permit application must be submitted the next working business day (§ R105.2.1). And ordinary repairs need no application at all — but the code draws that line tightly: ordinary repairs do not include cutting away a wall or partition, removing or cutting a structural beam or load-bearing support, changing a required means of egress, or altering water, sewer, gas, drainage, electrical or mechanical work (§ R105.2.2).
Your city can require a permit anyway
This exemption list is the 2025 statewide code, in effect since January 1, 2026, and it is a floor that cities are free to raise. A California jurisdiction adopts the state code and may amend it to require permits for work the state exempts — smaller decks, shorter walls, sheds under 120 square feet — and hillside, coastal and fire-hazard jurisdictions frequently do. Nothing here overrides a local ordinance that is stricter.
So the sequence that saves money is: measure the area, measure the worst-case height, decide whether it touches the house, check whether it lands under the exit door — then call your building department with those four answers. The call takes five minutes and settles it against the version of the code your city actually enforces.
