How to Tie a New Roof Into an Old Wall


Adding on to existing structures always poses challenges. How to attach new construction to old is always a part of the equation. When it comes to attaching a sloping roof to an existing wall, the device most commonly used is a ledger board. This is a horizontal lumber beam attached to the frame of the original structure to provide support for the rafters that should be supported at the lower end by the top cap of a new wall. This support wall must be framed before the ledger and rafters can be installed.

Things You'll Need

  • Tape measure
  • Chalk line
  • String level
  • Pencil
  • Circular saw
  • Pry bar
  • 2-by-6 treated lumber
  • Drill
  • Lag bolts
  • Impact driver
  • Joist and hurricane tie brackets
  • Treated deck screws
  • Measure up to the top face of the new roof on the existing wall. Subtract 1 inch and use a string level and chalk line to snap a line across the wall at that height, spanning the entire width of the new roof. Measure down 5 1/2 inches and mark a second line. Cut the siding and sheathing from this rectangle with a circular saw, set deep enough to cut through and skim the face of the studs beneath.

  • Pry the siding and other material from the slot you created in the wall, exposing the original studs. Mark the center of each stud with a pencil on the face of the siding above and below the cut area for easy location. Cut 2-by-6 treated lumber to span the width of the new roof. Fit this beam into the slot you created. This is your ledger board.

  • Mark the ledger with a square to indicate the center of each stud behind. Drill two 3/16-inch holes, 3 inches deep along each stud mark. Drive 1/4-by-3-inch lag bolts into each hole, using an impact driver. Drive the heads in flush.

  • Mark the ledger, starting from the left end, every 24 inches. Mark the support wall below, starting from the same end, every 24 inches. Use 2-inch treated deck screws and a drill to install a 2-by-6 rafter joist hanger on each mark on the ledger. Attach the left side, leaving the right side loose to fit the rafter. Install a hurricane tie on each mark on the wall cap to receive the end of the rafter.

  • Look over your blueprint to find the rafter end angle and length for your roof. Cut the angles at each end of every rafter, using a miter saw. Adjust the miter saw turn table to the correct angle by releasing the latch, either by pulling up on a trigger, or twisting the handle counterclockwise, depending on the saw, and align the indicator with the correct angle on the miter gauge.

  • Set one cut rafter into each joist hanger, hurricane tie bracket set and install the remaining screws to fasten the brackets to the rafters. Use one 2-inch treated deck screw in every hole.

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  • Photo Credit lumber 1 image by jimcox40 from
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