How to replace a rotted section of a support beam
Replacing a rotten or splitting section of a wooden support beam resting on a foundation wall involves working directly under overhead floor joists. Because it is often unclear how serious the structural damage is, people usually need to consult an expert to evaluate the beam before attempting a fix.
What the numbers show
Counted from the threads quoted below. How we count
- People have been saying this in most months since September 2026.
- This comes up 20.1× more often in r/HomeMaintenance than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Building/laminating pressure-treated lumber sandwiches with plywoodDid this help you?
- 2Ripping down 2x12s to match dimensionsDid this help you?
- 3Putting a piece of pressure-treated wood on either side of the beamDid this help you?
- 4Sistering a board behind it for peace of mindDid this help you?
- 5wrapping 2x4s around the column and using jacks to slightly raise itDid this help you?
- 6building an independent temporary post next to itDid this help you?
- 7using house jacks or a 20-ton jack to lift the wall and performing the wood replacement independentlyDid this help you?
- 8considering epoxy repairsDid this help you?
- 9Cutting the joists flush with the house, installing a ledger board, and building a new deck supported by cross-braced posts from the ground.Did this help you?
- 10Replacing the full length of the cantilevered joist by cutting into the house.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“Working on removing/repairing/replacing this second-story loft balcony. Several of the joists are rotten, is it possible to somehow shore the rotted joists without cutting into the side of the house for total replacement while still maintaining structural integrity?”source ↗
“Yeah. That was what I was guessing as i started pulling up the deck boards. I knew they were shot, wasn’t aware of how bad the joists were. It’s ok though. I hate money.”source ↗
“Hey all, have a wooden beam in my basement that has started to split. Wanted to get thoughts on how much of an issue this appears to be as I talk to my landlord about getting an expert out to look at it.”source ↗
“I am wanting to replace a 2’ rotten section of support beam on top of my foundation wall, under my floor joists.”source ↗
“Obviously the wood needs to be replaced (unless there is some magic epoxy) but I believe the wood is connected to the foundation with J bolts and I don’t know how to get them out or get new ones in.”source ↗
“Wish I could afford to pay a professional to do it but this is something I’m going to have to do on my own.”source ↗
“Just use a 20 ton jack with metal plate on top to lift wall and replace wood with pressure treated.”source ↗