Is your deck safe? Ledgers, footings, railings and stairs under Pennsylvania's code

Updated November 10, 2026 · KeystoneProGuide editorial team

What makes a deck safe?

A sound connection to the house, footings that will not heave or sink, framing sized for the load, and guards and stairs that stop people falling. Pennsylvania builds its residential code on the 2021 International Residential Code, which devotes a section to wood-framed decks, and adds its own stair dimensions. This guide sets out what those rules require, so that you can read a deck plan, ask a builder the right questions or look at your own deck with informed eyes. It is not a substitute for the inspection your municipality or a qualified inspector carries out.

When does a deck need a permit?

Pennsylvania's regulation exempts the installation of an uncovered deck whose floor is no more than 30 inches above grade, as long as the work does not violate a local law or ordinance. A covered deck, or one higher than 30 inches, needs a permit from your municipality or its code agency. Labor and Industry says over 90% of Pennsylvania's municipalities enforce the code locally, so the building office of your township or borough is where to apply.

In Philadelphia, residential decks up to 216 square feet, excluding roof decks, can get an EZ permit without submitting plans, provided the work follows the city's EZ standard.

How must a deck attach to the house?

Through a ledger bolted to the house's band joist, and the code is specific about each part. Under section R507 of the code:

• The ledger must be at least a 2-by-8 of pressure-treated or approved naturally durable lumber, No. 2 grade or better.
• It must not carry concentrated loads from beams or girders, and it must not be supported on stone or masonry veneer. A deck cannot simply be bolted to a brick or stone facing.
• The house's band joist it attaches to must bear fully on the house structure.
• Ledger fasteners, half-inch lag screws or bolts at spacings set by a table for the joist span, must be hot-dipped galvanized or stainless steel.

The code also wants the deck held against sideways forces. One prescribed method uses hold-down devices in at least two places, within 24 inches of each end of the deck, each rated for at least 1,500 pounds; another uses four devices rated at 750 pounds.

Water is the ledger's enemy. The code's wall-covering chapter requires flashing where porches, decks or stairs attach to a wood-frame wall or floor, applied shingle-fashion so water is shed outward, and the deck section requires flashing of corrosion-resistant metal at least 0.019 inch thick or an approved compatible material.

What about the footings and posts?

Deck footings must be concrete or another approved system sized for the loads, set at least 12 inches below undisturbed ground. Where the deck is attached to a frost-protected house, the footings must also be protected from frost, for example by extending below the frost line in the local design table. The code gives post sizes by height, species and the area each post supports. A free-standing deck can skip footings in narrow cases, such as joists resting on grade, or a deck of no more than 200 square feet on precast pier blocks with a walking surface no more than 20 inches up.

What materials and fasteners does the code require?

Lumber must be No. 2 grade or better and either preservative-treated or naturally durable, with cut ends and drilled holes in treated wood field-treated, and any treated wood in contact with the ground labelled for that use. Plastic composite deck boards, stair treads, guards and handrails must meet ASTM D7032 and carry a label saying so. Nails, bolts, lag screws and connectors must meet the code's corrosion-resistance table, which in practice means hot-dipped galvanized, stainless or other listed finishes.

How high must the railing be?

A guard is required on any open side of a walking surface, including a deck, porch, stair or landing, that is more than 30 inches above the floor or grade below at any point within 36 inches of the edge. Under section R312, the guard must be at least 36 inches high on a deck or porch, and at least 34 inches on the open side of a stair, measured from the line of the nosings. Openings must not let a 4-inch sphere through, with two exceptions on stairs: 6 inches for the triangle formed by riser, tread and bottom rail, and 4 3/8 inches on the open side of the stair. Insect screening does not count as a guard. The guard must also meet the code's load requirements and be supported as the deck section describes.

What are the rules for deck stairs?

Here Pennsylvania writes its own numbers. The state regulation sets a maximum riser of 8 1/4 inches, with no more than 3/8 inch variation within a flight, and a minimum tread of 9 inches, with treads in a flight varying by no more than 3/8 inch. Stairs must be at least 3 feet wide with 6 feet 8 inches of clear headroom. The model code adds a handrail on at least one side of any flight with four or more risers, between 34 and 38 inches above the nosings.

How can you check an existing deck?

Look at the points above in order: the ledger and its fasteners and flashing, the posts and footings, the guard's height, gaps and firmness, and the stairs. The deck builders' trade association, which promotes May as Deck Safety Month, publishes a 10-point consumer checklist covering corroding fasteners, decaying materials and loose railings, and says it is not a substitute for a professional inspection. It also estimates that 30 million U.S. decks have exceeded their useful life; that figure is the association's own.

What next?

If the deck needs work, questions to ask lists what to put to a builder, and the cost guide gives published deck prices. Builders are on the exterior remodeling directory page.

Sources

1. 34 Pa. Code 403.62. Permit requirements and exemptions., Commonwealth of Pennsylvania (Pennsylvania Code)
2. 34 Pa. Code 403.21. Uniform Construction Code., Commonwealth of Pennsylvania (Pennsylvania Code)
3. Chapter 3 Building Planning, 2021 International Residential Code, International Code Council
4. Chapter 5 Floors, 2021 International Residential Code, International Code Council
5. Chapter 7 Wall Covering, 2021 International Residential Code, International Code Council
6. Get permits without plans (EZ permits), City of Philadelphia
7. NADRA.org Urges Homeowners to Prioritize Deck Safety with Check Your Deck Campaign, North American Deck and Railing Association (NADRA)
8. Uniform Construction Code, Pennsylvania Department of Labor and Industry