The short answer first
For most raised or attached decks, yes.
A tiny, low, freestanding platform may be exempt where you live. Almost every other deck needs a permit. The exact line is local. No website can give you a national rule, because there is none.
This post explains the triggers that come up again and again. It then shows how five cities in our batch draw the line. Use it to plan. Confirm your own job with the office that will inspect it. This post is general information, not legal advice.
Trigger one: height above ground
Height is the most common trigger. A deck you can step onto from the lawn is a different risk from a deck at first floor door height with stairs.
Seattle draws the line at 18 inches. The city says a permit is needed if a deck is more than 18 inches above the ground. Other cities use 30 inches as a key figure for guards and permits. If any part of your deck sits high, in particular on a slope where one side is low and one side is high, assume a permit until the office says otherwise.
Height also brings guard rules. Decks above a set height need rails of a set height, with gaps small enough that a child cannot fall through.
Trigger two: attachment to the house
An attached deck is fixed to the house wall at a ledger board. That joint carries load and can let water into the wall if it is flashed poorly.
Permit offices care about this joint for good reason. Ledger failure is a known cause of deck collapse. Plans will show bolt pattern, flashing and the condition of the house rim board. A freestanding deck avoids the ledger, but it needs its own bracing and footings near the house.
If your plan attaches to the house, expect a permit.
Trigger three: size, footings and framing
New footings are a clear sign of permit work. So is new framing. Nashville puts it in plain terms. Any footing or framing replacement requires a permit there, and board replacement above 100 square feet does too.
Size alone can trigger review even for a low deck. A large platform changes drainage, setbacks and load. Some offices set a square foot line. Cross it and you file.
Electrical work is separate. Lights, outlets or a fan on a covered deck may need an electrical permit on top of the building permit. Ask at the design stage, not when the boards are down.
Trigger four: location on the lot
A deck can be safe in structure and wrong in place. Setback rules keep structures a set distance from property lines. Covered decks often must meet stricter setbacks than open decks. In Nashville, an uncovered deck may use a reduced rear setback of 10 feet, while a covered deck must meet full rear and side setbacks.
Easements are a hard limit. Decks should not sit over utility easements or drainage easements. Corner lots have extra side street rules in many codes.
Special land adds more checks. Seattle requires extra steps for decks in environmentally critical areas, such as landslide prone land. Historic districts in Boston, Nashville and Baltimore can add design review before a permit is issued. Flood zones can change footing and height rules.
What the permit process looks like
You or your provider file an application with a site plan. The site plan shows the lot, the house, property lines and the deck outline with distances. A framing plan shows footings, posts, beams and joists.
The office checks zoning first in many cities, then structure. You may need changes. Once the permit is issued, work starts. Inspections happen in stages. Footings are seen before concrete covers them. Framing is seen before boards hide it in low decks. A final visit checks rails, stairs and finish.
Keep the permit card and final sign off. You will want them when you sell or insure the home.
Our deck building service page walks through how a build and permit fit together.
What about repairs and like for like work
Small repairs often sit outside permits. Replacing a few worn boards, refixing a rail section without changing structure, and cleaning and coating a deck are common examples.
The line moves when repair becomes rebuild. New posts on new footings, a new ledger, reframing a span or replacing most of the surface push a job into permit ground. Our deck repair page explains that border in more detail.
If you are unsure, describe the whole scope in one go. Splitting a project into small parts to avoid a permit is a poor plan. Offices look at the total work.
Why owners skip permits, and why it backfires
Cost and time are the usual reasons. Permit fees are in fact modest next to a build cost in most cities. The wait is the larger pain, in particular in spring.
Skipping can cost more later. Stop work orders halt a half built deck. Work built without inspection may need to be opened up. A buyer survey can flag the deck and stall a sale. Insurance claims after a fall or collapse are harder with unpermitted work.
There is also a safety point. Inspection is a second set of trained eyes on footings and the ledger. Those are the parts you cannot see once the deck is done.
How to make permits painless
Start early. File in winter for a spring build where weather allows it. Keep the design simple for your first filing if the lot has setback or historic issues.
Pick a provider who files in your city often. They know the local forms, the plan style the office wants and the inspection booking method. Ask who meets the inspector and what happens if a stage fails.
For city specific starting points, read your city page. They are linked from our home page, which acts as the hub for the areas in this batch.
Frequently asked questions
What size deck can I build without a permit?
There is no single national size. Each city sets its own trigger by area, height or both. Seattle uses height over 18 inches as a main line. Other cities use a square foot figure plus height and attachment. The only safe answer for your lot comes from your city permit office or a provider who files there often.
Do I need a permit to replace boards on an existing deck?
Swapping a few boards is often treated as repair work with no permit. Replacing boards over a set area can trigger a permit, as Nashville shows with its 100 square foot rule. Framing, footing or ledger work almost always moves the job into permit ground. Describe the full scope to the permit office, not just the surface part.
What do deck inspectors actually check?
Inspectors check footings before they are filled, then framing, ledger fixing and flashing, joist hangers, rail height and spacing, and stair shape. They want to see that the deck will carry load and will not pull away from the house or let water into the wall. Final inspection happens after boards and rails are complete.
What happens if a deck was built without a permit?
Outcomes vary by city. You may be asked to apply after the fact, open up covered work for inspection, fix faults or remove work that cannot be approved. A sale or home inspection can flag unpermitted work. If you bought a home with such a deck, get a provider and, if needed, the permit office to advise on your options.
Common questions
What size deck can I build without a permit?
There is no single national size. Each city sets its own trigger by area, height or both. Seattle uses height over 18 inches as a main line. Other cities use a square foot figure plus height and attachment. The only safe answer for your lot comes from your city permit office or a provider who files there often.
Do I need a permit to replace boards on an existing deck?
Swapping a few boards is often treated as repair work with no permit. Replacing boards over a set area can trigger a permit, as Nashville shows with its 100 square foot rule. Framing, footing or ledger work almost always moves the job into permit ground. Describe the full scope to the permit office, not just the surface part.
What do deck inspectors actually check?
Inspectors check footings before they are filled, then framing, ledger fixing and flashing, joist hangers, rail height and spacing, and stair shape. They want to see that the deck will carry load and will not pull away from the house or let water into the wall. Final inspection happens after boards and rails are complete.
What happens if a deck was built without a permit?
Outcomes vary by city. You may be asked to apply after the fact, open up covered work for inspection, fix faults or remove work that cannot be approved. A sale or home inspection can flag unpermitted work. If you bought a home with such a deck, get a provider and, if needed, the permit office to advise on your options.