A ledger-attached deck is bolted to the house along one side. That saves a row of posts and footings, but it depends on a sound, properly flashed connection to the house framing. A freestanding deck stands on its own posts and beams on every side. It needs more footings, but nothing penetrates the wall of the house. The code allows either, and in some situations it requires a freestanding deck.
This guide explains what each approach involves, what the IRC requires of a ledger, and how the framing and footing counts change for the same deck. The code tables quoted here are a guide to how the rules work, not a design. Local amendments differ, so confirm details with your building department or an engineer.
How each design carries the load
On a ledger deck, the joists run from a beam on posts out in the yard back to a ledger board fastened to the house’s rim (band) joist. The house carries roughly half the deck’s weight. The connection has to resist the deck sliding down the wall and, in some designs, pulling away from it.
On a freestanding deck, a second beam on its own posts replaces the ledger, usually set a short distance from the house wall. Every pound goes to the ground through deck footings. The deck may sit close to the house, but it isn’t fastened to it.
What the code requires of a ledger
The IRC’s ledger rules are in Section R507.9. As reproduced in Anne Arundel County’s 2021 IRC deck guide, the main points are:
- Ledger material: at least a 2x8 nominal, of pressure-preservative-treated southern pine, incised treated hem-fir, or approved naturally durable lumber, No. 2 grade or better.
- No veneer: ledgers must not be supported on stone or masonry veneer.
- Flashing: ledgers must be flashed in accordance with R703.4. Flashing must be corrosion-resistant metal at least 0.019” thick, or an approved nonmetallic material compatible with the house and the decking.
- Band joist: the house rim joist must be at least 2” nominal solid-sawn spruce-pine-fir or better, or at least 1” × 9-1/2” Douglas fir or better LVL. It must bear fully on the primary structure.
- Fasteners: hot-dipped galvanized or stainless steel. Nails that rely on withdrawal resistance are not permitted.
- Prohibited attachments: the guide lists attachment to open-web floor trusses, to brick or stone veneer or a masonry chimney, and to an overhang or bay window.
The IRC text also says deck ledgers “shall not support concentrated loads from beams or girders” (IRC R507.9.1.1, 2018 New Jersey edition, via Lakewood Township).
Ledger fastener spacing
Fastener spacing in the code table depends on joist span, because longer joists put more load on the ledger. From the same Anne Arundel guide:
| Joist span | 1/2” lag, 1/2” max sheathing | 1/2” bolt, 1/2” max sheathing | 1/2” bolt, 1” max sheathing |
|---|---|---|---|
| 6 ft and less | 30” | 36” | 36” |
| 6’-1” to 8’ | 23” | 36” | 36” |
| 8’-1” to 10’ | 18” | 34” | 29” |
| 10’-1” to 12’ | 15” | 29” | 24” |
| 12’-1” to 14’ | 13” | 24” | 21” |
| 14’-1” to 16’ | 11” | 21” | 18” |
| 16’-1” to 18’ | 10” | 19” | 16” |
Spacings are on center. Fasteners are staggered top to bottom along the ledger, with minimum edge and end distances set out in a companion table (R507.9.1.3(2)). Note the sheathing column. Sheathing thicker than the column allows, or anything other than solid framing behind the ledger, puts you outside the prescriptive table.
Lateral connection
Separately, lateral loads have to be transferred to the ground or to a structure that can carry them. One prescriptive method uses hold-down tension devices: at least two per deck, within 24” of each end, each rated at not less than 1,500 lb. The other uses at least four devices rated at 750 lb each (Anne Arundel County deck guide). These connect the deck joists through the house rim to the floor framing inside. That often means opening a finished basement ceiling.
When a deck must be freestanding
The IRC states that where a deck is supported by attachment to an exterior wall, it must be positively anchored to the primary structure and designed for both vertical and lateral loads. Toenails and nails subject to withdrawal can’t be used. It then adds: “Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting” (IRC R507.8, 2018 New Jersey edition, via Lakewood Township).
In practice, a freestanding deck is usually the answer when:
- The house has brick or stone veneer where the deck would attach.
- The floor framing is cantilevered past the foundation, or the wall is an overhang or bay.
- The floor system uses open-web trusses, or the rim can’t be identified or reached.
- The rim joist is rotted, undersized or unknown, as can happen on older homes.
- The deck sits away from the house, around a pool or out in the yard.
Freestanding is also a reasonable choice when the attachment would be allowed but awkward. Examples include stucco that’s hard to flash properly, a wall full of windows and doors, or a homeowner who simply doesn’t want holes in the building envelope.
Worked example: the same 20 × 12 ft deck both ways
Take a 20 × 12 ft deck with joists at 16” on center running 12 ft out from the house. That gives 16 joists along the 20 ft side (240” ÷ 16 = 15 spaces, plus 1). The joist count is the same both ways. What changes is what supports the house end.
Ledger version
- Ledger: one 20 ft board (or two pieces) fastened to the house rim.
- Fasteners: a 12 ft joist span falls in the 10’-1” to 12’ row. That calls for 1/2” lags at 15” on center, or 1/2” bolts at 29” on center with up to 1/2” of sheathing. Over 240”, lags at 15” work out to roughly 16 or 17 fasteners. Bolts at 29” work out to around 9 or 10. The exact count depends on end distances and the stagger pattern.
- Outer beam: one beam on posts. With three posts at 10 ft spacing, the middle post carries about 60 sq ft of tributary area and each corner post about 30 sq ft.
- Footings: 3.
- Extras: flashing, removing siding at the ledger, lateral hold-downs.
Freestanding version
- No ledger. A second beam near the house replaces it.
- House-side beam: same size logic as the outer beam, sized from the beam span table (IRC R507.5) for the joist span and post spacing.
- Footings: 6, three on each beam line. Each house-side post carries the share of load that the ledger carried in the other version.
- Extras: posts near the house have to reach undisturbed soil. The ground beside a foundation is often backfill, so those holes can end up deeper than the others. Depending on height and local practice, taller freestanding decks may also need diagonal bracing or another way to resist racking.
So the trade is roughly three extra footings, three extra posts and one extra beam, against a ledger, flashing, house-attachment hardware and the work of opening up the wall. Price both with the deck framing calculator and deck footing calculator. The deck cost calculator gives the bigger picture.
Pros and cons side by side
| Ledger-attached | Freestanding | |
|---|---|---|
| Footings | Fewer | More (an extra beam line) |
| Framing | One beam | Two beams |
| House envelope | Opened; must be flashed correctly | Untouched |
| Allowed on brick veneer, overhangs, trusses | No (per prescriptive rules) | Yes |
| Moisture risk at house | Present if flashing fails | Essentially none |
| Sway resistance | House helps; lateral hardware required | Comes from posts, beams and any bracing |
| Movement relative to house | Moves with the house | Can move independently; leave a gap at the wall |
Ledger details that cause trouble
Most deck connection failures come down to a few predictable mistakes.
- Missing or reversed flashing. Water running behind the ledger rots the rim joist from the outside, where nobody sees it. Flashing has to lap under the siding above and over the ledger, so it sheds water out and away from the wall.
- Nails instead of lags or bolts. The code prohibits nails subject to withdrawal for this connection.
- Ledger over thick sheathing, spacers or siding. The fastener table only covers specific sheathing thicknesses.
- Ledger carrying a beam. Concentrated beam loads on a ledger aren’t allowed under the prescriptive rules.
- Wrong fastener coating. Treated lumber is corrosive to plain steel. The code calls for hot-dipped galvanized or stainless fasteners.
Freestanding details that cause trouble
- Footings in backfill near the foundation, which can settle.
- Too little bracing on a taller deck, which feels wobbly even when the vertical load path is fine. AWC’s DCA 6 Prescriptive Residential Wood Deck Construction Guide is a widely used reference for deck framing details. Use the edition and details your jurisdiction accepts.
- No gap at the house. A freestanding deck built tight against the siding traps debris and moisture.
- Assuming no permit is needed. Freestanding decks usually still need a permit. Only the narrow exceptions for small, low decks change the footing rules. See deck footings and frost depth for those limits.
Choosing between them
If your house has a solid, accessible rim joist behind wood or vinyl siding, a ledger deck is usually the simpler and cheaper build, provided you flash it properly and install the lateral connection. If the house has veneer, overhangs, trusses, an unknown rim or a wall you don’t want to open, freestanding is the safer choice and sometimes the only permitted one. Either way, the joist layout is the same. Deck joist spacing covers sizing, and how to plan a deck walks through permits and drawings.
Frequently asked questions
Is a freestanding deck safer than a ledger deck?
Neither is inherently safer when built to code. A correctly attached and flashed ledger is a proven connection. A freestanding deck removes the risk of a bad ledger, but it relies on more footings and on enough bracing. Most problems come from poor execution, not from the choice of design.
Can I attach a deck ledger to brick?
Not under the prescriptive IRC rules when the brick is veneer. Ledgers must not be supported on stone or masonry veneer. Some solid masonry walls can take an engineered attachment, but that’s outside the standard tables. Most decks against brick-veneer houses are built freestanding.
Does a freestanding deck need footings below the frost line?
Usually, yes. The 2021 IRC exempts only narrow cases, such as small, low decks bearing on precast pier blocks. Many jurisdictions require frost-depth footings for any deck on posts. Check your local deck handout before deciding.
How far should a freestanding deck be from the house?
The code doesn’t set one distance. Builders typically leave a small gap so the deck can move independently and water and debris can drain. Make sure the gap doesn’t create a trip hazard at a door threshold. Also keep the house-side footings out of loose backfill.