How to Replace a Rotten Structural Beam

A structural beam is a wood beam that is used to support the weight of a roof or other load-bearing wall. In a roof, the beams run horizontally across the top of a house, with the rafters attached on top. Over time, the structural beams in a house home can succumb to rot or insect damage and need replacing. Replacing a structural beam requires professional work that only an experienced contractor should handle. If an old beam simply needs strengthening, you can brace it with a new one.

Inspect the beams in your home to look for signs of damage.

Step 1

Locate the rotten wooden beam in the attic of your house. 

Step 2

Push the tip of a screwdriver into the rotted area to see how far it penetrates.  Repeat the process at multiple locations to determine if the beam can be fixed. If the screwdriver goes in more than 1/4-inch, you must call a licensed contractor to replace the beam. 

Step 3

Wipe down the wooden beam and clean the rotted areas with a rag.  Measure the length of the beam so a new beam can be cut to size. Mark the desired cut location on a new beam and line up the blade of a circular saw with the mark on the beam.  Cut the new beam to length.

Step 4

Spray wood epoxy over the damaged area of the old beam, starting on one end and working to the other. 

Step 5

Line up the new beam with the old one.  Drill and screw the two beams together with a power drill and wood screws. Space the screws every 8-inches to be sure the new beam is securely attached. 

Things You Will Need

  • Screwdriver
  • Tape measure
  • Pencil
  • Wooden structural beam
  • Circular saw
  • Wood epoxy
  • Power drill
  • Wood screws
  • Safety goggles


  • Always wear safety goggles when you are working with a circular saw.
  • Make sure that problems with dampness or insects are remedied before you replace or strengthen an old beam.

About the Author

Alexander Callos began writing in 2005 for "The Lantern" at The Ohio State University and has written for various websites, including Bleacher Report, Top Ten Real Estate Deals and Columbus Sports. He has published articles for CBS Sports, SI.com and other websites. He graduated in 2007 from The Ohio State University with a bachelor's degree in public affairs journalism.

Photo Credits

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