How Is a Roof Attached to a Concrete Block Wall Ledger Board?

About Ledgers on Block Walls

• Ledgers are horizontal boards fastened to a wall surface. For projects that involve heavy loads, such as roof and patio cover additions, builders use thick, solid lumber for ledgers, often 2-by-10 or larger. Builders typically use concrete expansion anchors or adhesive-mounted anchor bolts to secure ledgers to concrete block walls. For exterior applications, such as roof additions, you should use preservative-treated or waterproofed lumber to construct a ledger board. Additionally, builders often seal the joint between the lumber and the concrete blocks with caulk before attaching roof rafters or joists.

Roof Framing Members

• Several types of roof framing members apply to roof additions on concrete block walls. Roof framing options include solid lumber, engineered wood products and steel framing materials. The right type of framing material for a particular project depends on the design of the roof and local conditions, such as high wind or snow loads. You should discuss your design with your local building authority, a builder, architect or engineer before attaching joists or rafters to a concrete block wall.

Joist and Rafter Hangers

• Hanger brackets are the most common methods of attaching a roof to a ledger. Hanger brackets are roughly U-shaped metal angles that mount to the face or top edge of a ledger with joist hanger nails. Roof framing materials, such as rafters or joists, fit within the saddle-like, U-shaped bodies of the hangers. Builders secure roof framing to the hangers through screw holes that line the brackets' sides. Joist hangers are relatively easy to install. After hoisting joists or rafters into hangers, workers have both hands free for nailing and making adjustments.

Ledgers as Headers

• As an alternative to metal joist hanger brackets, some building codes might allow builders to use ledgers as headers for roof framing members. The term "header" typically refers to lintels that span the tops of door or window openings. Using a ledger as a header means that rafters or joists rest on the top edge of the ledger or on top of a small, second ledger nailed to the face of the primary ledger. In either case, direct nailing or toe-nailing fastens the rafters or joists to the face or top edge of the ledger. Acceptable construction methods vary according to local codes; check with your building authority before using a ledger as a header.