Reinforcing a Basement Beam

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Things You'll Need

  • Jack posts

  • 4-foot level

  • Adjustable wrench

  • Steel plates

  • Drill

  • Lag bolts

  • Circular saw

  • Chisel

  • Epoxy wood filler

  • Nails, 4 inches long

  • Hammer

Basement beams support the entire house.
Image Credit: Hans Hansen/Lifesize/Getty Images

Basement beams are one of the most important elements in the structure of a house. Many houses feature a beam that is supported by posts running down the center of the basement ceiling. This beam supports the centers of the floor joists above it. In large houses, the joists may be jointed, with the beam supporting the nailed together joists. If you think your basement beam isn't up to the task of supporting your house, it's a very good idea to take steps to make it stronger.


Step 1

Install vertical jack posts from the basement floor to the underside of the beam to help support it. If there are already jack posts present in your basement, space the new ones evenly between the old ones to distribute the load. Put the jack post in place, ensure that it's perfectly vertical by checking it with a 4-foot level, then turn the bolt on the top using an adjustable wrench to raise the top plate tight against the bottom of the beam. Turn the bolt until the post is extremely tight, but not so much that you shift the beam.


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Step 2

Install steel plates along the sides of the basement beam. These can be small plates that are placed over areas that have been damaged or are supporting particularly heavy loads, or full-length steel plates that run the length of the beam. Drill holes every 8 inches along both edges of the steel plate. Drill corresponding pilot holes into the beam. Hold the steel plate in place and bolt it to the side of the beam with lag bolts.


Step 3

Repair rotting parts of the beam that may be weakening it by replacing them with new wood. Support the beam on both sides of the repair area with temporary jack posts before cutting into it. Remove the rotted area by cutting across the beam with a circular saw with its blade set to the depth of the rot. Make consecutive cuts about 1 inch apart along the rotted area, then remove the material with a flat chisel. Cut a new piece of wood to fit snugly into the cut out area. Cover the surfaces of the cut with epoxy wood filler, put the new piece of wood in and nail it into place with 4-inch-long nails. Leave it for 24 hours so the epoxy dries and sets, then remove the temporary jack posts.


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