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Rotted Structural Wood Repair: Sill Plates, Joists & Beams
How do you repair rotted structural wood? You remove the damaged wood and either bolt a new board alongside the old one (called sistering), cut out and replace the rotted section, or replace the entire member.
The tricky part is that rot hides in the crawl space where nobody looks, quietly weakening the wood holding your floors up. A bouncy floor, or one sloping toward the middle of the room, is often the first clue.
The short version: rotted structural wood is very fixable when caught in time. A free crawl space inspection identifies exactly which members are damaged and whether sistering, partial replacement, or full replacement is the right call.
Call (318) 585-2003 – Free Inspection
Why Wood Rots Under Louisiana Homes
Wood does not rot on its own – rot is decay caused by fungi, and fungi need three things: wood, warmth, and moisture. Louisiana crawl spaces deliver all three for most of the year.
The sill plate – the horizontal board sitting directly on the foundation wall – takes the worst of it, as the lowest wood in the house and the first to wick up ground moisture.
How to Tell If Your Structural Wood Is Rotted
The simplest check is the probe test. Press a flat-head screwdriver into the wood in your crawl space – especially sill plates and joist ends. Sound wood resists and barely dents; rotted wood lets the screwdriver sink in.
- Floors that sag, slope, or feel bouncy underfoot – often the first sign the joists or beam below have lost strength.
- Doors and windows that suddenly stick or will not latch.
- Cracks in drywall, especially above door frames.
- A musty, damp smell that never quite goes away.
- Visible sagging or dipping across a room.
Sill Plate Repair: The Most Common Job We See
The sill plate anchors your house framing to the foundation, so when it rots, the wall above loses its solid base. Replacing a sill plate section typically runs $3,000 to $10,000.
Floor Joist Repair: Sistering vs. Partial Replacement
Floor joists are the parallel boards carrying your floors, and when they rot the floor above starts to sag. The standard fix is sistering: a new joist of the same size is bolted alongside the damaged one so the new board carries the load.
Sistering a single joist typically costs $200 to $600; full replacement runs $500 to $1,500.
Main Beam Replacement
The main beam is the heavy timber the floor joists rest on, carried by piers along its length. Beam replacement typically costs $4,000 to $12,000 and takes two to three days for most homes.
What Rotted Wood Repair Costs in Shreveport
The surprise for many homeowners is the moisture fix on top of the wood work: sealing a crawl space, improving drainage, or adding a sump system can add a few thousand dollars – but skipping it is what leads to repeat rot.
How to Stop Rot From Coming Back
Repairing rotted wood without fixing the moisture is like patching a roof leak by putting a bucket under it. The most effective step is controlling water around and under the house.
Frequently Asked Questions
Can rotted structural wood be repaired, or does it have to be replaced?
Minor rot can be fixed by sistering a new member alongside the damaged one. Rot that runs deep means cutting out the bad section or replacing the whole board.
How much does it cost to replace a rotted sill plate?
Replacing a rotted sill plate section typically runs $3,000 to $10,000, depending on linear feet damaged and how much jacking the house needs.
How can I tell if a floor joist is rotted?
Do the screwdriver test: press a flat-head screwdriver into the wood. Sound wood resists, while rotted wood lets it sink in easily.
Will sistering a joist fix a sagging floor?
Usually yes, when the rot is localized. Sistering adds a full-strength member alongside the damaged one.
Is rotted wood in a crawl space dangerous?
It can be. Rotted joists, beams, and sill plates lose load-bearing strength, which means sagging floors and, in advanced cases, structural failure.
Do termites cause wood rot?
Not exactly – rot is caused by fungi feeding on damp wood, while termites eat the wood itself. Louisiana homes often have both problems at once.
How long does structural wood repair take?
Most jobs take one to three days. Sistering a few joists is often a single-day job, while sill plate or beam replacement takes two to three days.
Get a Free Structural Wood Inspection in Shreveport
If your floors are sagging, your doors are sticking, or you have never looked under your house, a free inspection is the fastest way to find out what is going on. Call Pelican Foundation Repair at (318) 585-2003.
Pelican Foundation Repair 6118 Fairfield Ave, Shreveport, LA 71106, USA 318-585-2003 https://foundationrepairshreveport.com/