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Building Code Reference

Got a CRC R507.10 correction?

Deck guard post connection

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CRC R507.10 covers how deck guards attach to the deck. Guards must meet R301.5, which sets a 200-pound concentrated load applied in any direction at any point along the top, and R321. Where guards are supported on deck framing, the load must reach the deck joists through a continuous load path. A post fastened to the side of a joist or beam requires that member to be connected to the adjacent joists so it can’t rotate, and connections relying only on fasteners in end-grain withdrawal aren’t permitted. 4x4 wood posts carrying guard loads can’t be notched at the connection. Top-mounted guards connect to the framing or blocking per the manufacturer’s instructions.

How to fix it

  1. Add a guard post connection detail to the deck plan sheet

    Create a detail at 1/2"=1' scale or larger on the structural or deck detail sheet. Label it 'Guard Post Connection Per CRC R507.10'. The detail must show the post, the rim joist or band board, the through-bolt, washers, and any blocking. This is the most common missing item on first submittals. Without a named detail pointing to the guard post location, the plan-checker cannot verify compliance and will issue the correction regardless of whether the field install would be correct.

  2. Specify the post connection and don't notch 4x4 posts

    R507.10 names no fastener, but it bars connections relying only on fasteners in end-grain withdrawal and bars notching 4x4 guard posts at the connection. The common detail is a carriage or hex bolt through the post and rim joist, with a washer and nut on the far side; 1/2-inch diameter is the norm for a 4x4 or 4x6 post. Show this explicitly in the detail with a label like '1/2" dia. through-bolt w/ 2" sq. washers each side.' If you previously showed lag screws with no blocking or engineering, replace them with the through-bolt callout on the revised sheet.

  3. Add solid blocking between rim joist bays at each post location

    When the post bears against a single-ply rim joist, the lateral load can pry or split the rim joist under the 200-lb design force. Solid blocking (full-depth, same species and size as the floor joist) installed in the bay immediately inboard of the rim joist at the post location transfers the load into the floor system. Show the blocking in plan view with a note: '2x full-depth solid blocking at guard post locations per R507.10.' R507.10.1.1 requires the joist or beam carrying the post to be connected to the adjacent joists so it cannot rotate.

  4. Or specify a code-listed post base with the ESR number

    If you're using a proprietary post base (Simpson Strong-Tie ABA, PBS, or similar), look up the product's ICC Evaluation Report number. The ESR will list the tested lateral load capacity for each fastener pattern and post size. Your detail must include: the base model number, the ESR number, the post size (e.g., 4x4), the fastener schedule per the ESR, and a note confirming the rated lateral capacity equals or exceeds 200 lb at the top of the guard post height. A detail that just says 'post base per manufacturer' without the ESR number will be kicked back.

  5. Label guard post spacing on the plan

    R507.10 connection details are reviewed alongside the guard spacing. Show post spacing on the deck plan in plan view (typically 4 feet on center maximum for a code-compliant baluster fill-out). If post spacing is tight, the 200-lb point load assumption still applies to each post independently. Note the spacing in a general note and cross-reference the connection detail. A guard that passes R321.1.2 (height) but fails R507.10 (post connection) gets two separate correction items.

  6. For engineered connections, include the calc or stamp

    If a standard through-bolt-plus-blocking detail does not fit your framing (deep LVL rim, steel moment frame, non-wood framing), have the engineer of record provide a connection calculation or stamp the detail. The calc must show: the 200-lb concentrated load from CRC Table R301.5 applied at the top of the guard, the moment arm to the connection, the resulting force on the fasteners, and the fastener capacity. A stamped detail sheet with 'Designed for CRC Table R301.5 guard load per R507.10' is cleaner than embedded calcs, but either will pass review.

  7. Resubmit with a revision cloud on the updated detail

    Mark all changed sheets with a revision cloud and a revision triangle. On the deck detail sheet, cloud the new guard post connection detail. On the plan sheet, cloud any new blocking callouts. Note the revision date in the title block. Most plan-check departments will not re-review an entire deck set for a guard post correction; if you cloud only the relevant items, the checker can find the fix in under two minutes and close the correction.

Take the CRC R507.10 fix steps with you

All 7 steps in one email, so you have them on site instead of on this page.

Why you got flagged

Plan-checkers flag R507.10 most often because the detail simply isn’t on the drawings. A contractor submits a deck plan that shows guard posts at the required height, but nowhere on the sheet is there a callout showing how the post attaches to the rim joist, outside joist or beam. Without that detail, the plan-checker can’t confirm a continuous load path for the 200-lb guard load, and the correction goes out.

A second common flag is a connection that stops at the rim. A post bolted or lagged to a single rim joist, with nothing tying that rim back to the joists behind it, lets the rim roll outward when someone leans on the guard. R507.10.1.1 requires the joist or beam carrying the post to be connected to the adjacent joists to prevent rotation. It also bars connections relying only on fasteners in end-grain withdrawal, such as nails or screws driven through the rim into the ends of the joists.

Third, many details show a 4x4 post notched to sit over the rim. R507.10.2 prohibits notching a 4x4 wood post that supports guard loads at its connection to the supporting structure. Use a larger post if the design calls for a notch, or keep the 4x4 full section.

Post bases and top-mounted guard systems from proprietary manufacturers (Simpson or similar) come with evaluation reports showing tested values. R507.10.1.2 requires top-mounted guards to connect to the deck framing or blocking and be installed per the manufacturer’s instructions, so the plans need the model, the report number and the fastening that report requires.

A fifth scenario shows up on raised decks where the guard post is bolted to the face of a beam instead of a rim joist. The same anti-rotation rule applies to beams, and the plan-checker will often ask for an engineered connection.

The official code

California Residential Code R507.10, Exterior Guards (deck guard post connections) (2025 CRC, Title 24 Part 2.5)

Read the source →

Common questions

Are lag screws banned for deck guard posts under R507.10?
Not by name. R507.10 doesn’t specify a fastener type. It requires a continuous load path to the deck joists, a connection from the carrying joist or beam to the adjacent joists so it can’t rotate, and no connections that rely only on fasteners in end-grain withdrawal. A lag screw into the face of a rim with nothing tying the rim back fails those tests. The detail reviewers see most often is a through-bolt with blocking or a hold-down tying the rim to the joists. If you show lags, back them with engineering or a tested product.
Does R507.10 apply to second-story deck guards or only ground-level decks?
Any deck guard. Guards are required where a walking surface is more than 30 inches above the floor or grade below within 36 inches horizontally of the open side (R321.1.1), and every required guard must carry the 200-lb load from Table R301.5. That load doesn’t change with deck height. Plan-checkers do tend to look harder at elevated decks, so a clear connection detail matters more there.
What size through-bolt does R507.10 require for a 4x4 guard post?
None. R507.10 sets performance rules (load path, anti-rotation connection, no end-grain withdrawal, no notched 4x4 posts) rather than a bolt diameter. A 1/2-inch carriage or hex bolt with washers is a common choice for a 4x4 post, often paired with a hold-down. Whatever you pick, size it to carry the Table R301.5 guard load at the actual guard height, and show it on the detail.
Is blocking always required, or can I use a double rim joist instead?
Where the post attaches to the side of a joist or beam, R507.10.1.1 requires that member to be connected to the adjacent joists to prevent rotation. A doubled rim joist is stiffer, but by itself it doesn’t tie the rim back to the joists. Show how the rim is connected to the adjacent joists at each post, for example with full-depth blocking or a listed hold-down, and note it on the detail.
Do proprietary post bases like Simpson ABA count as a compliant R507.10 connection?
They can, if the product is rated for guard posts in the way you’re using it. For guards mounted on top of the decking, R507.10.1.2 requires a connection to the deck framing or blocking, installed per the manufacturer’s instructions. Write the model number, the evaluation report number and the fastening it requires on the detail. A note that just says “post base per manufacturer” isn’t enough for the plan-checker to verify.
What if my deck has steel posts, composite guards or a non-wood rim joist?
R507.10.4 says other guards must follow the manufacturer’s instructions or accepted engineering principles, and R507.10.3 sends plastic composite guards to R507.2.2, which requires compliance with ASTM D7032. For steel posts, steel framing or unusual rim conditions, have an engineer design the connection and stamp the detail or provide a calculation showing the Table R301.5 guard load reaches the framing.
Can I use the American Wood Council’s DCA 6 guard post detail?
Check the guard height first. DCA 6 calls for hold-down anchors with a minimum allowable tension of 1,800 pounds for a 36-inch maximum guard height. The 2025 CRC requires deck guards of at least 42 inches (R321.1.2), so the DCA 6 detail doesn’t directly cover a California guard. Use a product rated for your guard height, or have the connection engineered.

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