The ledger is a crucial component in deck construction, serving as the wood member that attaches the entire deck to the house. Its proper installation is vital, as an improperly installed ledger is one of the most common causes of deck failure. This failure can result from inadequate or improper fastening to the supporting structure or from a failure to correctly flash the installation to prevent rot. Both issues can worsen over time, seriously compromising the integrity of a deck.

To put this in perspective, according to buildingonline.com’s “Outdoor Deck and Porch Injury Study,” nearly 15% of all deck-related injuries resulted from structural failure, and of those 60% were due to the deck connection back to the house.

Code-Compliant Ledgers

First, let’s look at what the codes and reference guides require or recommend as the minimum ledger size:

• DCA 6 and 2021 IRC, R507.9.1.1: Minimum 2×8, but must be equal to or greater than the joist size. It must also be less than or equal to the house band or rim board.
• NADRA: Minimum 2×12 (Section 7, 7a).

For all codes, the band (or rim) joist in the supporting structure must be a 2x band or structural element that can adequately take the loads of an attached structure. Band joists must be fully supported by a wall or sill plate below. This means you cannot attach a ledger to a cantilevered floor system.

Per 2021 IRC (R507.2.1), ledgers must be pressure-preservative-treated southern pine, incised pressure-preservative-treated Hem-fir, or approved, naturally durable, No. 2 grade or better lumber. DCA 6 (Table 5, footnote 5) specifies that deck ledgers shall be a minimum 2×8 pressure-preservative-treated No. 2 grade lumber or other approved materials as established by standard engineering practice.

Attaching the Ledger to the Structure

Ensuring the ledger is securely fastened to the primary structure is crucial for safety and stability. Here, we’ll explore the minimum ledger fastening options and general requirements based on various building codes and standards.

Section 507.8 of the 2021 IRC, Table 5 of DCA 6, and Section 7d of NADRA specify that this connection cannot be made with nails. Instead, it must be made with a code-accepted positive connection, such as Simpson Strong-Tie® screws or listed ledger screws or bolts. We will look at a few of these options. The deck must also be secured to the house to be restrained against lateral loads. You can read more about this in the fourth blog in this series.

Fastener and Connection Options for Deck Ledger Attachment

Code requires that the deck ledger be positively anchored to the primary structure, and designed for both vertical and lateral loads. Again, these connections cannot be made with toenailing. The fasteners used to attach the ledger to the structure must be hot-dipped galvanized or stainless steel to withstand environmental elements and pressure-treated contact (2021 IRC Section R507.9.1.3). Additionally, the fastener heads should not be countersunk. In order to avoid joists or joist hangers, screws or bolts can be moved up to 3″.

1. Code-Compliant Structural Ledger Screws

Simpson Strong-Tie has many structural screws accepted for attaching a ledger. This information can be found in one of the company’s engineering letters, L-F-100DCKLIV25. When out discussing how to properly attach the ledger, I like to recommend the Strong-Drive® SDWS™ Timber screw. The aforementioned engineering letter gives all of the information that a design or installer needs in order to properly space the screws for the project’s condition.

There are some other perks to using these screws as well. These include:

• Faster and easier installation.
• No predrilling required (except at ledger ends).
• Suitable for loads greater than 40 psf live loads, making them ideal for snow areas.
• Added versatility as they can be driven into the home structure’s sole plate or studs.

1. Traditional Lag Screws

When attaching the ledger back to the home, 1/2″-diameter lag screws with washer are permitted to be used. While this is the more traditional way of achieving this connection, keep in mind that there are some additional requirements when using a lag screw. For starters, a lag screw requires not just one, but two different predrills. A 1/2″-diameter lag requires a 1/2″-diameter clearance hole in the ledger and a 5/16″-diameter pilot hole in the band/rim. Do not drill a 1/2″ hole into the band. When installing a lag screw, it is best to avoid using a hammer drill.

Some additional information to be aware of in using lag screws:

• For ledger board fastener spacing and clearances, refer to 2021 IRC Section R507.9.1.3, Figure R507.9.1.3(1), Figure R507.9.1.3(2) and DCA Figure 19.
• Maintain a 5″ vertical space max, 2″ min. edge at top, 3/4″ min, edge at bottom, and 2″ min, end.
• The tip of the lag screw must extend beyond the inside face of the band joist.
• Carriage bolts are not
• Stacked washers may be used (1/2″ max,).
• Clearance holes for 1/2″ bolts should be 17/32″ to 9/16″ in diameter.
• Threads must extend beyond the nut and washer on the inside face of the house band/rim.

2. Attaching the Ledger to a Structure with Masonry Veneer

We’ve discussed ledger connections when we can achieve a positive attachment between the wood deck and the sound wood framing of the supporting structure. But what if the primary structure has an exterior veneer made of brick, masonry, tile, glass, or stone? These wall elements cannot sustain added vertical load. Stick-on brick or stucco siding is not what we are referring to here; the masonry veneer we’re discussing must be attached to the backing (via a brick tie) and will have an air gap between the brick and the supporting structure.

Code Provisions for Masonry Veneer

There are three specific code provisions to consider when trying to attach a deck to a structure that has a brick veneer:

• 2021 IRC, Section R507.9.1.1: Deck ledgers shall not be supported on stone or masonry veneer.
• 2021 IRC, Section R507.8: If a positive connection to the primary structure cannot be verified during inspection, the deck must be self-supporting.
• 2021 IRC, Section R703.8.3: Masonry veneer shall not support any vertical load other than the dead load of the veneer above.

Because the code does not allow attaching the ledger directly to the brick veneer, the options you are left with are either a freestanding deck or using a code-listed connector that bypasses the brick and attaches to the structural rim/band joist.

As mentioned, to adhere to these provisions, you can make your deck self-supporting, by introducing structural posts near the face of the supporting structure. While this is often a good solution, it can present some challenges, especially when you have a walk-out patio below and need to avoid blocking doors and windows. Also, footings must go below the frost line and be in undisturbed soil. This requirement can be challenging because the soil around the home’s exterior footing is “disturbed.”

Because the code does not allow attaching the ledger directly to the brick veneer, another solution is the new BVLZ™ brick veneer ledger connector. This product provides a proper ledger board attachment at the face of the brick veneer while meeting code requirements for a sound connection to the primary structural framing of the home. It does not bear on the masonry veneer; instead, the Strong-Drive SDWH™ Timber-Hex HDG screws (included in the BVLZ kit) bypass the veneer and act in tension, while the compression strut also bypasses the veneer and bears on the rim board. This connection creates a truss action, supporting the ledger without bearing on the masonry.

The BVLZ is tested in accordance with AC13 both as a single connection and as a component of a deck system. We also evaluated the shear and withdrawal capacity of SDWH screws into the rim board with single fastener testing in accordance with AC233. Keep the BVLZ in mind for installations with brick veneer.

4. Ledger Attachment to Concrete or Grout-Filled CMU

When attaching the ledger board to a solid foundation consisting of concrete or grout-filled masonry, minimum 1/2″-diameter code-compliant expansion, epoxy, or adhesive anchors with washers may be used. Alternatively, the Simpson Strong-Tie stainless-steel Titen HD® (THDSS) may be used and is available in either Type 304 or Type 316 stainless steel. Vertical placement of the Titen HD anchors through the ledger and into the solid foundation or wall should be in a staggered configuration and spaced horizontally based on loading, ledger size, and solid wall specifications. Additional information can be found in L-A-THDSSLDGR and L-A-LDGRGFCMU25.

Flashing and Weatherproofing

Deck collapses occur nationwide, often during gatherings when the deck is subjected to extra weight. While the attachment of the ledger back to the structure is crucial, so is how we protect that connection from water damage. Proper flashing of the ledger is critical to avoid trapping moisture, which can cause wood decay and rot, potentially leading to deck failure. Flashing is key to a safe, long-lasting deck.

Before choosing your approach, check with your building department for local code requirements. 2021 IRC Section R703.4, DCA 6, and NADRA all give guidance on how to properly flash the deck ledger. While they are all trying to achieve the same goal, the following sequence is prescribed by NADRA:

6. Remove siding from the exterior wall down to the exterior sheathing.
7. Install self-stick, self-sealing flashing on the wall, extending 2″ above and below the ledger and 6″ past the ends.
8. Fasten the ledger to the header material.
9. Install more self-stick, self-sealing flashing over the ledger.
10. Install Z (cap) flashing (metal or plastic).
    1. Take caution and do not use aluminum flashings with pressure-treated lumber unless a durable barrier material separates the aluminum from the wood. Preferably, use G185 galvanized steel.
11. When reinstalling siding, ensure it is kept off the decking material.

In extremely damp climates, using spacers to encourage water flow away from the wall is another method. This is made possible by the strength of structural screws, which are stronger than old lag-bolt counterparts. Careful caulking further safeguards against moisture. To that end, the overall practice of flashing and weatherproofing your ledger to help avoid wood decay, rot, and corrosion is key to ensuring that you will have a safe, sturdy deck for years to come.