How to tie in a new roof to an existing structure?

Written by mark morris
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How to tie in a new roof to an existing structure?
A shingle pitch shed-style roof is the easiest to add on. (casita en Canada image by Pablo Armelles from

One of the simplest roofs to use when adding on is the single pitch shed roof. Found on porches and single story appendages of multiple story homes, it is a good choice for the do-it-yourself carpenter. The tie-in is made using a strip of lumber known as a ledger board, connected to the frame of the original structure and serving much the same purpose as one side of the ridge beam of a typical gable roof. Be certain to locate the studs properly when attaching to achieve proper structural strength.

Skill level:

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Things you need

  • Tape measure
  • String level
  • Chalk line
  • Circular saw
  • 2-by-6-inch treated lumber
  • Drill
  • Lag bolts
  • Socket wrench
  • Joist hangers
  • Hurricane ties
  • Scrap 2-by-4-inch lumber
  • Treated-deck-screws, 2 inches long
  • 1-by-6-inch lumber
  • Decking
  • Flashing
  • Felt
  • Shingles

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  1. 1

    Mark the top and bottom horizontal line of your 2-by-6-inch ledger board 1 inch below the desired height of the top of your new roof where it meets the existing wall. To do this, use a string level and chalk line. Cut along both lines with a circular saw through the siding and sheathing, setting the depth of cut to skim. Do not cut into the face of the studs. Use a hammer and pry bar to remove the cut siding, exposing the studs.

  2. 2

    Position the 2-by-6-inch treated lumber into this slot and drill ¼-inch pilot holes, two into each exposed stud. Drive 4-by-1/4-inch lag bolts into each hole using a socket wrench. Tighten the bolts until the heads are flush with the surface of the board.

  3. 3

    Start at one end and attach a ridge line, 2-by-6-inch joist hanger bracket using two inch treated deck screws every 16 inches on centre. Attach the left side of each bracket, leaving the right side open. Add an extra bracket flush with the far end, if it is not an even 16 inches.

  4. 4

    Install hurricane tie down brackets along the top of the wall where the lower end of your roof will rest. Attach them with 2-inch treated deck screws. Start from the same end you started from on the ledger board to keep the brackets even with each other.

  5. 5

    Set a 2-by-6-inch piece of lumber a little longer than needed for your rafters into the first pair of brackets, with the bottom end resting in the hurricane tie and the bottom corner of the top end against the bottom of the ledger board. Place a scrap of 2-by-4-inch lumber with its narrow edge against the ledger board and its wide face on the side of the rafter you just placed. Mark a line down the outside edge of the 2-by-4-inch board with a pencil onto the rafter to mark the angle for the rafter ends.

  6. 6

    Cut the end of the rafter off with a circular saw and temporarily replace it in the bracket with cut end flush against the ledger board. Measure the distance from the ledger board along the bottom of the temporary rafter to a point 6 inches past the end of the wall and mark the rafter on its bottom edge. Use the cut rafter as a template to cut the same angle on the end of a second rafter.

  7. 7

    Place this cut end aligned with the mark on the first rafter's bottom end. Mark the angle onto the board so the rafter tail at the bottom matches the angle at the ledger board, creating a parallelogram. Cut the rafter tail off on the line. Mark the remaining rafters using the first rafter as a template and screw one into each set of brackets using 2-inch treated deck screws in each hole, fastening the loose right side of the bracket in place.

  8. 8

    Attach a 1-by-6-inch board along the rafter tails to tie the frame together. Use two 2-inch treated deck screws in each rafter tail. This completes the tie-in process for your roof frame. Add decking, flashing, felt and shingles to complete the roof.

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