Check Local Building Codes
Building codes exist to ensure safety. Understanding them before you design prevents costly changes later. Most code requirements are straightforward once you know what to look for.
Quick Summary
1-2 hours
36-42 inches
4" max
Building dept.
Why Building Codes Matter
The Real Cost of Ignoring Codes
Building without permits or outside code requirements can result in: fines up to $500/day until corrected, forced removal of the deck at your expense, denied homeowner's insurance claims if someone is injured, and major problems when selling your home. It's not worth the risk.
Building codes aren't arbitrary bureaucracy - they're based on decades of data about what causes deck failures. The most common deck collapse causes (ledger connection failure, railing failure, structural overload) are all addressed by code.
Where to Find Your Local Codes
Local Building Department (Best Source)
Your city or county building department is the definitive source. They can tell you exactly what's required in your jurisdiction.
- Call or visit in person - staff are usually helpful
- Ask for a deck permit handout or checklist
- Request the local amendments to the IRC (International Residential Code)
- Ask about specific requirements for your lot (historic districts, HOA areas)
Online Municipal Code
Many cities post their building codes online. Search for "[your city] building code" or "[your city] residential deck requirements."
HOA Requirements
If you have an HOA, check their covenants. Many HOAs have additional restrictions on deck size, location, materials, and appearance beyond building codes.
Common Deck Code Requirements
While codes vary by location, most jurisdictions follow the International Residential Code (IRC) with local amendments. Here are the most common requirements:
Setback Requirements
Setbacks define how close your deck can be to property lines and other structures.
Typical Side Setbacks
5-10 feet from side property lines
Typical Rear Setbacks
15-25 feet from rear property line
Easement Restrictions
Usually no structures in utility easements
Lot Coverage Limits
Total structures may not exceed % of lot (varies)
Railing Requirements
Minimum Railing Height
Most codes require 36 inches minimum for residential decks. Some areas (California, others) require 42 inches. Commercial properties typically require 42 inches.
Maximum Baluster Spacing
The space between balusters (vertical spindles) cannot exceed 4 inches. This is the "4-inch sphere rule" - a 4-inch ball should not pass through any opening in the railing system.
When Railings Are Required
Railings are required when the deck surface is more than 30 inches above grade. This is measured at any point around the deck perimeter.
Structural Requirements
Footing Depth (Frost Line)
Footings must extend below the frost line to prevent heaving. This varies dramatically by location:
| Southern states (FL, TX, AZ) | 12-18 inches |
| Mid-Atlantic (VA, NC, TN) | 18-24 inches |
| Midwest (IL, OH, PA) | 36-42 inches |
| Northeast (NY, MA, NH) | 42-48 inches |
| Northern tier (MN, WI, ME) | 48-60 inches |
Ledger Attachment
The ledger board must be attached to the house's rim joist with specific fasteners (typically 1/2-inch lag screws or through-bolts). Proper flashing is required to prevent water intrusion. This is the most failure-prone connection on a deck - codes are very specific here.
Joist and Beam Sizing
Beam and joist sizes depend on span length and spacing. Most codes reference span tables in the IRC. For example, a 2x10 joist at 16" spacing can typically span 12-14 feet. Your plans must show these calculations.
Stair Requirements
Minimum Tread Depth
10 inches (nosing to nosing)
Maximum Riser Height
7.75 inches (some areas 8 inches)
Minimum Width
36 inches clear between rails
Handrail Height
34-38 inches above stair nosing
Critical: All risers must be the same height (within 3/8 inch). Uneven steps are a leading cause of falls. Calculate total rise divided by desired riser height to determine number of steps.
When Permits Are Required
Most jurisdictions require permits for decks. Here are the common thresholds:
Typically Requires a Permit
- Any deck attached to the house
- Any deck more than 30 inches above grade
- Decks over 200 square feet (varies by jurisdiction)
- Decks with roofs or pergolas
- Any electrical work (lighting, outlets)
May Not Require a Permit (Varies)
- Freestanding ground-level decks under 200 sq ft and under 30 inches high
- Simple platform decks less than 30 inches above grade
- Replacement of existing deck boards (no structural changes)
Always verify with your building department - "no permit required" thresholds vary significantly by location.
Questions to Ask Your Building Department
When you call or visit, have these questions ready:
- 1What are the setback requirements for my zoning district?
- 2What is the frost line depth in this area?
- 3What railing height is required (36" or 42")?
- 4What information must be included in my permit application?
- 5What inspections are required and at what stages?
- 6Are there lot coverage or impervious surface limits?
- 7Do I need engineered drawings, or are homeowner plans acceptable?
Frequently Asked Questions
Do I need a permit to build a deck?
In most jurisdictions, yes. Permits are typically required for any deck attached to a house, any deck over 30 inches above grade, or any deck over 200 square feet. Some areas require permits for all decks regardless of size. Building without a required permit can result in fines, forced removal, or problems when selling your home.
What is the 4-inch rule for deck railings?
The 4-inch rule means that the space between balusters (vertical spindles) cannot exceed 4 inches. This prevents small children from getting their heads stuck between balusters. The same 4-inch maximum applies to the space between the deck surface and the bottom rail, and to any triangular openings on stairs.
How deep do deck footings need to be?
Deck footings must extend below the frost line to prevent heaving. This depth varies by location: 12-18 inches in Southern states, 36-48 inches in the Midwest and Northeast, and up to 60 inches in parts of Minnesota and Alaska. Your local building department can tell you the exact frost line depth for your area.
What is a setback requirement?
A setback is the minimum distance your deck must be from property lines, easements, or other structures. Typical residential setbacks are 5-10 feet from side property lines and 15-25 feet from rear property lines. Setbacks ensure adequate space between buildings for fire safety, emergency access, and privacy.