It is very important that you use the correct size and type of fasteners to install your ledger board. Your deck will depend on the load-carrying capacity of these screws or bolts to support hundreds of pounds and prevent the deck from ripping away from the house. Make sure the bolts are compatible with pressure-treated wood. They should have a washer or a large head. You will usually need to pre-drill a 5/16” pilot hole into the rim joist if you are using ½” lag bolts. Your bolts or screws should be long enough to extend at least ½” past the board you are attaching to. They are usually installed in a zig-zag pattern.
Ledger Board Fastener Spacing Schedule
|Joist Span||Fastener Spacing, On Center|
|1/2" Lag Bolt||SDWS Timber Screws||Thru/Carriage bolts|
• Ledger: 2 x pressure-preservative-treated No. 2 grade Hem-Fir lumber or better. Douglas Fir-Larch, Southern Pine.
• Sheathing: 15⁄32" or 7⁄16" OSB sheathing.
• Rim joist: 2 x _ Spruce-Pine-Fir lumber or 1" minimum Engineered Wood (EW) Rim. EW Rim material must be solid LVL, LSL or PSL.
Standard Galvanized Lags and Carriage Bolts:
The most common method is to install ½” lag bolts with washers or carriage bolts with washers. You will usually need the length of the bolt to be at least 4”- 6" to penetrate through the 2x ledger board, the house sheathing and into the solid house rim. Never counter sink bolts. This will significantly weaken the ledger board. In a ledger board application, a ½” x 4” lag bolt was tested to provide 180 lbs support of allowable shear load per screw.
Be sure to know what you are connecting to. Standard bolt patterns are based on a solid connection to a solid-sawn and fully supported band joist in the home. Lag screws that hit wall plates or studs may not be comparable.
The fasteners must be compatible with pressure-treated lumber to prevent corrosion. Typically, you will need to install your bolts alternating high and low 2" from the top and bottom of the ledger board. As a rule of thumb, bolts can be spaced 16" on center for supporting joist span up to 12' in length. Longer joists will require tighter bolting patterns.
The built-in washer head eliminates the need for an additional washer, saving time and money. This is the preferred fastener by most professional deck builders. It’s available in 3 5/8” and 5” lengths and comes in 50- and 250-piece cartons.
Concrete Expansion Bolts: