Do You Need a Permit to Build a Deck? Code Basics
When a permit is required
Rules are local, but the pattern under the International Residential Code is consistent. A permit is normally required when a deck is attached to the house, is more than 30 in above grade at any point, or is larger than a small exemption (200 sq ft is a common figure) that applies only to detached, ground-level platforms that do not serve a required exit door. Repairs that replace boards like for like usually do not need one; replacing the frame does.
Building without a permit saves the fee and risks a stop-work order, a demolition order at resale, an insurance dispute after a collapse, and a difficult conversation with the buyer’s inspector. The fee is a small line in the deck cost calculator; the risk is not.
What gets inspected
| Inspection | When | What they look at |
|---|---|---|
| Footing | Holes dug, before concrete | Depth to frost line, diameter, bearing soil, spacing per plan |
| Framing | Frame complete, before decking | Ledger fasteners and flashing, beam and joist sizes and spans, hangers, post connections, bracing |
| Final | Deck complete | Guard height and baluster spacing, stair rise and run, handrail, lighting at stairs |
The code items that cost money
- Guards. Required where the walking surface is more than 30 in above grade; 36 in minimum height for residential decks, with no opening that passes a 4 in sphere. This is the railing line in any estimate.
- Stairs. Maximum rise 7¾ in, minimum tread depth 10 in, risers within ⅜ in of each other, a graspable handrail 34–38 in above the nosings on stairs with four or more risers. The stair calculator lays these out.
- Ledger. Attached to the band joist with ½ in lag screws or through-bolts at a prescribed pattern, flashed to keep water out of the wall, never to brick veneer or to a cantilevered floor. Where the house cannot take a ledger, the deck goes freestanding — a second beam and twice the footings.
- Footings. Below the local frost depth, on undisturbed soil, sized for the load. Deep frost lines are why the same deck costs more in the north.
- Spans. Joist and beam sizes come from span tables for the species and spacing; posts 6 × 6 above a certain height; lateral load connectors at the ledger in many jurisdictions.
What to have ready
A plan view with dimensions, footing locations, beam and joist sizes and spans, ledger detail, guard and stair details, and a site plan showing setbacks from property lines. Many departments publish a prescriptive deck guide that does the engineering for standard cases; a deck that fits it is approved quickly, and one that does not may need a stamped design.
Build an itemised estimate for a new deck — footings and posts, framing, decking with waste, fasteners, railing by the foot, stairs by the step and labour scaled for height — from prices you collect locally, so the total fits your lumber yard and your contractors rather than a national average.
Frequently asked questions
Do I need a permit for a ground-level deck?
Often not, if it is detached from the house, under 30 inches above grade, below the local size exemption, and does not serve a required exit door. Attach it to the house or raise it past 30 inches and a permit is almost always required. Check locally, because exemptions differ.
How high does a deck railing need to be?
Under the International Residential Code a guard is required where the deck is more than 30 inches above grade, at least 36 inches high for a house, with no opening that a 4 inch sphere can pass through. Stairs need a graspable handrail 34 to 38 inches above the tread nosings when they have four or more risers.
What happens if I build a deck without a permit?
Nothing, until it matters. A neighbour complaint or a resale inspection can bring a stop-work or demolition order, fines, and a requirement to open up the frame for inspection. An insurer can also contest a claim after a failure. The permit fee is one of the smallest lines in a deck estimate.
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