The long beams that provide the main structural support for the floor can cost $200 to $500 per room or $10 to $67 per square foot to repair. A full replacement costs $5,000 to $20,000. If you're only repairing individual joists, expect to pay $100 to $300 per joist.
Repairing rotting joists costs between $1,000 and $5,000, while foundational issues are typically the most expensive type of repair, with an average cost between $1,800 and $6,500.
We do not recommend trying to remove and replace the rotten floor joist yourself. Once you identify the problem, or if you want to call professionals to find the problem, you can be sure that highly-trained contractors will do the best job possible.
The first thing you will want to do is determine the condition of your joists. This will help you assess whether you need to repair, support, or replace them. A common sign of compromised joists is uneven floors. But these could be the result of flooring or subflooring defects.
Labor. The labor fees to install subflooring are usually between $25 and $30 per hour, but may vary based on your location and whether the job is straightforward or complex. Additional work—like removing existing flooring and subflooring, hauling old materials, or preparing a surface—costs extra.
A typical price for a Joist is $168 but can range from approximately $18 to $575.
Because structural damage to your floor joists often requires professional tools and knowledge, you'll likely need to hire a contractor. When repairing hardwood floor joists, expect to pay $65 to $100 per hour on labor alone. Projects tend to take anywhere from 5 to 24 hours.
While it may be possible to fix your floor joist yourself, it is often a job that is best left to professionals. Another issue is that many homeowners fix the floor joist, but do not fix the underlying issue, leaving the other floor joists in their home at risk of developing the same damage.
To repair floor joists, the damaged joist is sistered together with a new piece of wood. Usually, the new piece of lumber spans the length of the old one. At times when this isn't possible, shorter pieces are used instead (this is sometimes referred to as scabbing).
These are the first sign of impending issues that could threaten the structure of your floor and wider household. Damaged floor joists are something you should take seriously because neglecting them can lead to further damage.
High Humidity
For example, uncovered crawl space vents or loose vent covers and crawl space doors can let water into your home and increase humidity. Over time, this kind of humidity can cause a damp environment and allow fungal spores to take root, thus spreading in exposed wooden joists.
Foundation damage caused by shifting or settling earth or sagging floors caused by rotting floor joists are typically not covered by homeowners insurance. If the damage is caused by flooding or an earthquake, you'll typically require separate coverage.
What you need to know is floor joists bear the weight of the entire home. While walls usually only bear part of the weight, with some not bearing any weight at all. Floor joists are important for this reason alone.
Humidity and moisture can cause severe problems for floor joists. When exposed to damp conditions, wood can rot and become weak. This can lead to sagging floors and even floor collapse. Also, damp environments attract pests like termites and carpenter ants that can damage floor joists.
The best way to repair deck joist rot is to sister new treated lumber onto a deck joist that has minimal wood rot. If just the top 1 inch of the joist is rotted, you can repair the rotted deck joist by screwing on a treated 2x4 to the existing floor joist.
However, in most cases you can stop wet rot by treating the timber with a fungicide. The treatment of wet rot involves applying a fungicide during the drying out period. The fungicide can be supplied in concentrate form (usually for professionals for use over large areas) or as a ready to use product.
Replacing a floor joist is a big job. If you don't have any carpentry experience, you may want to call a professional carpenter to handle the project. Replacing a floor joist incorrectly may weaken the structural integrity of your house, putting your safety and your house's value at risk.
According to Angi and HomeAdvisor, the cost to replace a subfloor ranges from $428 to $2,978, with a national average of $572.
In general, homeowners insurance covers subfloor water damage. However, it must be caused by one of the perils listed in your insurance policy. If you have an HO-2 policy, your building, including the floor, is protected against various threats, such as a ruptured water heater or pipe.
The most common lumber sizes for floor joists are 2x6, 2x8, 2x10, and 2x12. Larger joists can span across wider areas. For example, a 2x6 joist would have a 12-foot, 6-inch maximum span, and a 2x10 joist would have a 21-foot maximum span.