Rafters

• A roof's structure consists of a combination of components holding it up. These include ridge boards and rafters, or trusses. The weight includes the sheathing, roofing material, equipment and snowfall. A broken rafter can be repaired by the "scab and prop" method.
  
  Simply fasten a horizontal piece of two-by-six board to the rafter. The scab must span the board on both sides of the break and be secured into the good portions of the board. Don't use nails, but three- to four-inch screws. Make the scab the same size as the original rafter. Insert the screws in a zigzag pattern, which will provide added strength to the repair.
  
  Provide additional reinforcement by securing vertical support braces on both sides of the broken rafter. Fasten the braces to the ceiling joist below.
  
  

Beams

• Install a temporary support beam before removing the damaged beam. Place wood blocks underneath the rafters close to the roof beam. Make a temporary beam by fastening a pair of two-by-six boards together with scab boards. Each two-by-six must span the length of the original beam. Attach the temporary two-by-six beams to the blocks. Brace the roof with four-by-four posts.
  
  Place a post under each rafter and raise the posts in place with bottle jacks, which are small hydraulic handle-operated jacks. You can also use a pair of two by fours fastened together for the support braces. Remove the damaged beam. Jack the roof up enough to install the new beam.
  
  

Columns

• Use a four-by-four post as a temporary brace to support the beam near the spot where you will be removing or repairing the post or column. Detached the support beam from the column and remove it. It may be necessary to raise the roof to remove the column. Put the new beam in place
  
  

Sheathing

• Mark the area that is to be removed. Use a reciprocating saw to cut out the damaged roof sheathing. Examine the rafters to determine their condition and repair them if necessary. Replace the sheathing with similar material of the same thickness. This will ensure that the roof has uniformity. Attach boards of similar size to the rafters around the edges to provide solid support for nailing in the new piece of sheeting.