How to Head Off a Rafter

Rafters provide the structural support and create the slope of a roof. Rafters typically reach from outside walls to the ridge (the peak) in one continuous piece. If you need to cut rafters in the middle of this span by installing anything wider than the space between rafters, such as a dormer, a skylight or other large roof penetration, you need to support the cut ends. Heading off rafters is the process of installing framing to support the ends of the cut rafters and create a rigid frame around the perimeter of the opening. Both the top and bottom of such openings, and typically one side, will need to be headed off.

Things You'll Need

• Tape measure
• Circular saw
• Reciprocating saw
• Small square
• Hammer
• 12d framing nails
• 2x lumber the same dimension as the rafter
• Extension ladder

Instructions

Cutting the Opening in the Roof

1. Determine the size of the finished opening your project requires and locate the area on the roof. Adjust one side of the opening to align with an existing rafter location, if possible, to minimize the number of rafters you will need to cut. Check local codes for any requirements to double up the two adjacent full rafters (stringers) and whether headers need to be single or double.

2. Use the circular saw to cut the sheathing and any roofing material in the area of the new opening.

3. Remove the roofing and sheathing from within the opening to expose the section of rafter(s) which will need to be cut away and headed off.

Installing the Headers

1. Mark the rafters to be cut so the header will line up with the edge of the cut sheathing and the thickness of the header will set away from the opening. For wood framing, this would be 1 1/2 inches up from where the sheathing is cut at the top and 1 1/2 inches down from the edge of the sheathing at the bottom. For a double header, these marks would be 3 inches each.

2. Cut the rafters squarely from beneath using the reciprocating saw, and remove the waste material and any remaining nails.

3. Measure the distance horizontally across the opening between the full rafters where the headers will install and cut the top and bottom headers to length from the 2x lumber.

4. Nail each header into place using three to five nails in each end. Nail through the side rafter into the header, and though the header into the cut rafter using a staggered nailing pattern. Use toe nailing (angled nailing) if necessary.

5. Measure the distance between the upper and lower header on the side where the sheathing is unsupported, and cut a member to that length. Position the piece flush with the cut edge set away from the opening and nail into place in the same manner as used in Step 4 .

Tips & Warnings

• If double stringers are required, install the second member on the side away from the opening after installing the headers.

• When using the reciprocating saw, be careful not to penetrate the sheathing or roofing material.

References

• WAC: Roof Framing for wood framed construction
• Graphic Guide to Frame Construction: Roof Framing