Framing and Rough Carpentry (C-5) · Lesson 4 of 5

Deck Ledger Fastening: Lag Screw Spacing and Lateral Ties

"Deck Ledger Fastening: Lag Screw Spacing and Lateral Ties" is lesson 4 of 5 in the Framing and Rough Carpentry (C-5) Learning Hub. It opens with "Why the Ledger Connection Is the Critical Joint" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Why the Ledger Connection Is the Critical Joint
  2. What the Ledger and Band Joist Must Be (R507.9.1.1 to R507.9.1.5)
  3. Reading the Spacing Table (Table R507.9.1.3(1))
  4. Placement: Stagger, Edge, and End Distance (Table R507.9.1.3(2))
  5. The Lateral Load Connection (R507.8 and R507.9.2)

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Divide by the maximum spacing and round up" through "Actual spacing".

What you'll be able to do

  • Explain the main idea of "Deck Ledger Fastening: Lag Screw Spacing and Lateral Ties" in plain language you can use on the exam.
  • Apply this step with confidence: "Reading the Spacing Table (Table R507.9.1.3(1))".
  • Apply this step with confidence: "Placement: Stagger, Edge, and End Distance (Table R507.9.1.3(2))".
  • Apply this step with confidence: "The Lateral Load Connection (R507.8 and R507.9.2)".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Deck Ledger Fastening: Count the Lag ScrewsElevation of a 16 ft ledger on the house band joist (zigzag pattern, 12 screws) 17.1 in. o.c. 2 in. minimum end distance; 188 in. between end screws Deck joist span 10 ft, so 18 in. maximum 1/2 IN. LAG SCREW, TABLE R507.9.1.3(1) Deck joist spanMax o.c. (40 psf live) 6 ft30 in.8 ft23 in.10 ft18 in.12 ft15 in.14 ft13 in.16 ft11 in.18 ft10 in. THE COUNT Ledger 16 ft = 192 in. 192 - 2 - 2 = 188 in. end to end 188 / 18 = 10.44, round up to 11 spaces Screws = 11 + 1 = 12 Actual spacing 188 / 11 = 17.1 in. Total = 12 lag screws 12 staggered 1/2 in. lag screws at 17.1 in. o.c. (18 in. max) Plus 2 lateral hold-down devices, 1,500 lb each, within 24 in. of the ends Never on stone or masonry veneer (R507.9.1.1); flash per R507.9.1.5 Source: 2025 CRC Table R507.9.1.3(1) and (2), and R507.9.2CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Why the Ledger Connection Is the Critical Joint

A deck ledger is the board bolted to the house that carries one end of every deck joist. Roughly half of the deck's weight hangs on this one connection, and it must also resist the deck trying to pull away from the house. Ledger failures are a leading cause of deck collapses, and the 2025 California Residential Code (CRC) R507.9 therefore specifies the ledger, band joist, fastener spacing and lateral connection instead of leaving it to the framer's judgment.

Step 2: What the Ledger and Band Joist Must Be (R507.9.1.1 to R507.9.1.5)

The ledger is a minimum nominal 2x8, No. 2 grade or better, pressure-preservative-treated Southern pine, incised pressure-preservative-treated hem-fir, or decay-resistant naturally durable wood. It may not support concentrated loads from beams or girders, and it may not be supported on stone or masonry veneer. The band joist behind it must be a minimum 2-inch nominal solid-sawn spruce-pine-fir or better, or a minimum 1-inch nominal engineered wood rim board, and must bear fully on the primary structure. Flashing goes above the ledger and extends at least 2 in. above it and at least 4 in. beyond the ledger face (R507.9.1.5). Lag screws are installed with a 1/2 in. hole through the ledger and sheathing and a 5/16 to 3/8 in. hole through the band joist, and the tip of each lag screw must fully extend beyond the inside face of the band joist (Table R507.9.1.3(1) note d).

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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