Does the deck need a permit?
The 2021 International Residential Code, section R105.2, exempts a deck from a building permit only when all of these are true:
- The deck is not more than 200 square feet
- It is not more than 30 inches above grade at any point
- It is not attached to the dwelling
- It does not serve the required exit door
Miss any one of those and the model code expects a permit. Cities amend this constantly — some drop the size limit, some still require a zoning review for an “exempt” deck. An exemption from the permit is not permission to ignore setbacks. Call the building department and ask which code year they enforce.
What the site plan has to show
Municipal deck checklists (the plot-plan half, not the framing half) converge on the same items:
| Show this | Why |
|---|---|
| Property lines, easements, and the house | The deck is reviewed against the lot, not as a floating rectangle |
| Deck location against the house | Attached and detached decks are often different rules |
| Overall length and width | Area is how they test the 200 sq ft exemption and lot coverage |
| Distances from the deck to each nearby lot line and to other structures | This is the setback check |
| Height of the walking surface above grade | Guards, and often the permit itself, turn on 30 inches |
| Stairs, if they land in a setback or a yard the deck itself does not | The stair is part of the projection |
| North arrow, scale, and the property address | A sketch with no scale is a common reject |
You will usually also submit a floor plan and a section: footing size and depth, posts, beams, joists, ledger and lateral connection if the deck is attached, and guard details. ZoneMapper draws the site plan. It does not replace those framing sheets. IRC section R507 is the prescriptive deck chapter most departments hand you for that second drawing.
Setbacks: attached decks are often treated like the house
Zoning, not the IRC deck chapter, sets how close the deck can sit to a lot line. Ask one question before you draw: does this deck use the house setbacks or an accessory-structure setback?
- Attached decks are often pulled into the principal-building setbacks, including the front yard. A deck off the back of the house can still fail if it crosses the rear setback.
- Low or detached platforms are sometimes allowed closer to a side or rear line, and sometimes still banned in the front setback.
- Easements (utility, drainage) are not buildable just because the zoning setback is met. Show them if your survey has them.
There is no national deck setback. A rear-yard number you saw online is someone else's ordinance.
Patios on grade
A concrete, paver, or stone patio that sits on the ground is not a deck. The IRC permit exemptions for sidewalks and driveways are widely read to cover on-grade patio surfaces, so many towns do not want a building permit for a flush patio. Two things still apply:
- Zoning and impervious cover. The patio can count toward a lot-coverage or stormwater limit even when no building permit is required. A zoning permit or a simple plot plan is common once you cross that percentage.
- If it is raised more than a few inches, or it has a roof, it starts to look like a deck or porch and the deck rules come back.
Draw a patio the same way as a deck footprint, label it “on-grade patio,” and set its surface. In ZoneMapper, new shapes start as impervious. In Layers, change Surface to Permeable or Gravel (uncounted) when your code does not count that surface toward impervious cover, or Not counted to leave it out of both totals.
How to draw it free in ZoneMapper (about 45 minutes)
1. Open a map or the deck template
In the app, choose Start from template and pick Deck if you want a worked example: a house, a deck, a dimension, and placeholder setbacks you replace. Or enter your address for aerial imagery and a GIS parcel outline where coverage exists, or upload your survey. The template is sample geometry — a banner stays up until you clear it.
2. Trace the lot
If a parcel outline loaded with the address, compare it to your survey. Otherwise use Lot boundary, click each corner, then Finish lot boundary. Setbacks and lot coverage calculate from that outline, not from a shape drawn with Polygon.
3. Draw the house and the deck
Draw the house and mark it Existing in Layers (dashed stroke). Draw the deck with Rectangle and enter the real width and depth in feet. Leave it Proposed. If the stairs land outside that rectangle, draw them too.
4. Dimension and label the height
Use Dimension for the deck's length and width and for the distance to each lot line it approaches. Use Text for the height above grade and whether the deck is attached. Enter your required setbacks in the Setbacks panel so the restricted zone is shaded before you export.
5. Export the PDF
Fill in the title block (address, owner, date) and export. Submit this sheet with the framing plans your checklist asks for.
Common reasons deck site plans get sent back
- No dimensions from the deck to the property lines
- Height above grade missing, so the reviewer cannot tell if guards or a permit apply
- The deck drawn across a setback or an easement
- Stairs omitted, then found in the setback at inspection
- Only a site plan submitted when the checklist also requires footing and framing sheets
FAQ
Can I use the site plan as my only drawing?
For a zoning check, often yes. For a building permit on a deck that is attached, over 30 inches, or over 200 square feet, expect a second set of construction details. Ask which sheets are required before you pay the fee.
Do I measure the setback to the deck edge or to the house?
To the deck, including stairs and any roofed portion. The house already has its own distances. Reviewers want the new work dimensioned.
Does the deck count toward lot coverage?
Sometimes the footprint counts, sometimes only roofed area counts, and sometimes an uncovered deck under a certain height is excluded. That is a zoning definition. Draw the area either way so you can run the percentage once you know the rule.
More permit guides
ZoneMapper is a drafting aid. Deck exemptions, setbacks, and coverage rules vary by jurisdiction and by local amendments to the building code. Verify them with your building department before you submit or build. Construction details such as footings, ledgers, and guards are outside this site plan.