Fairfax County Typical Deck Details, Explained

What the handout is

Typical Deck Details is a Fairfax County Land Development Services publication that shows pre-approved construction details for a simple deck. It's based on the 2021 Virginia Residential Code, and the current version is 2021.0, dated January 5, 2024. When a deck matches the details exactly, the handout can stand in for custom engineering on a permit application. Its details can't be deviated from without prior county approval.

It's also the best plain description of what a code-built deck looks like in Fairfax County, which makes it useful even if you're just trying to judge an existing deck. Most of the items below are things you can check on your own deck with a flashlight and a tape measure.

What it covers, and what it doesn't

The details apply to residential, single-level decks only. On its design considerations page, the handout says it is not approved for privacy screens, planters, built-in seating, surface-mounted guard posts or hot tubs, and it prohibits multi-level decks that share posts and footings. If your plan includes any of those, the deck needs its own design. A screened porch is a different project too: the county's permit guidance lists screen porches alongside decks and sunrooms as new additions to an existing home.

Footings: 24 inches and solid ground

Footings must bear on solid ground at least 24 inches below grade, and deeper if solid ground isn't found there. Inspectors verify the bearing before concrete is placed. A footing within 5 feet of the house wall has to bear at the same elevation as the house's own footings, which matters on homes with basements, where the house footings are far deeper than 24 inches. Concrete must be at least 3,000 PSI. Our footing guide explains why the depth matters.

The ledger: the connection that matters most

• The ledger must be at least a 2x8 and no smaller than the deck joists.
• Siding must be removed where the ledger attaches, and continuous flashing installed.
• Attaching a ledger to brick or stone veneer, open-web floor trusses, chimneys, overhangs or bay windows is prohibited. Those situations need a free-standing or engineered deck instead.
• Lead anchors are prohibited.

Of everything in the handout, the ledger section is the one most often violated by older decks. Our ledger safety guide covers how to look at yours.

Guards

A guard is required when the deck surface is more than 30 inches above grade at a point 36 inches out from the edge. Guards must be at least 36 inches high, and no opening may allow a 4-inch sphere to pass. Notching guard posts is prohibited, and posts need hold-down anchors rated at least 1,800 pounds. Remember that surface-mounted guard posts aren't approved under the handout at all.

Stairs

Stairs must be at least 36 inches wide. Risers can be no more than 8¼ inches and treads at least 9 inches, with no more than ⅜ inch of variation between steps. A handrail 34 to 38 inches high is required once there are four or more risers, and each stairway must be lit. These are Virginia numbers, not the national model code's, which our stair and railing guide explains.

Hardware, fasteners and power

Hangers and connectors must be stainless steel or G-185 galvanized (sold under names like Zmax or Triple Zinc). Fasteners must be hot-dip galvanized, stainless, or approved for use with treated lumber. Modern treated lumber is hard on ordinary steel, so this isn't a fine point. The handout also requires at least one electrical receptacle along the deck perimeter.

The three inspections

1. Footing: holes dug and ledger board attached.
2. Framing: posts, beams and joists installed, before the decking goes on. This inspection may be omitted if the bottom of the joists is more than 48 inches above grade and all connections are visible at final.
3. Final.

The approved plat and plans must be on site for inspections. Building inspections can be reached at 703-222-0801, and inspections are scheduled through PLUS online, by phone, or at the Herrity Building.

What it means for a repair

The handout is written for building decks, but it's a useful yardstick for an old one. A deck with a nailed ledger, no flashing, notched guard posts and shallow footings may still look fine from above. When we assess a Fairfax deck for repair, these are the items we compare against. If the gaps are in the surface and railings, repair usually works. If they're in the ledger and footings, replacement is often the better answer. Fairfax County says permits are required before building a new or replacing an existing deck; for repairs, we confirm with the county for your specific scope.

If you live in Herndon or Vienna

The Town of Herndon runs its own building inspections and publishes its own standard deck construction details, so Herndon decks go through the Town rather than the County. Vienna decks use the County building permit, plus a separate Town of Vienna zoning review.