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 predrill 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: