Originally posted 12/26/19, updated 8/6/2021
When your floors slope, ripple, or sag, you know there’s something wrong with the structure of your home. There are a number of causes, and they vary depending on how your home was built. Founded in 1996, Acculevel has repaired structural wood flooring systems in thousands of customers’ homes. We want you to benefit from our years of experience, and explain what you can expect to pay when you have to fix a sagging floor.
Acculevel has an $800 job minimum for most of the repair types done in this area; in the last 12 months, our customers paid an average of $5900 to repair sloping or sagging floors. This number can be misleading, because there are a wide range of variables that can affect costs.
In this article, we will break down the repair methods and costs associated with each. Our intention is to help you make an informed decision about what you need to repair your home. The first and most significant is the construction type of your floor system. This is because concrete slab floors don’t have the wooden structural elements that come with a basement or crawl space.
FYI: Pricing provided in this article includes both material and labor costs.
The Cost to Fix Sagging Concrete Slab Floors
If the soil under your foundation shifts or erodes, the slab will sink. In most cases, slab jacking is the best and most reliable repair method. Slab jacking is a type of concrete lifting that fills any voids under the slab, then raises the floor back up. The costs for slab jacking begin at $2000, and will increase depending on how much material is needed and how large the area is to complete the repair. For more details on the slab jacking method and how it works, we have an explanatory article here.
On some occasions, slab jacking is not a good fit. If the soil below your slab is compromised and too soft for several feet, slab jacking is going to be a temporary and insufficient repair. This is because the soft soil will continue to settle, making your floors sink again- sometimes within months of slabjacking. In those instances, the best option is helical piers, because piers are installed to tie into undisturbed soil more than 20 feet below your home.
The price of piers ranges from $1600-$2400 per pier, depending on placement, depth, load requirements, and if they are installed by machine or by hand. For detailed information about helical piers, you can read our companion article about their use and costs. In some cases, both methods are needed.
The Cost to Fix Sagging Floors in Basements and Crawl Spaces
This may be stating the obvious, but all of the structural wood framing in your home is interconnected. This means that one component may not be the only one at fault. In our experience we’ve found that multiple parts of the flooring system are usually affected. The direction or type of sagging floor usually highlights the area of greatest concern, which is how we explore the types of repairs below.
There are multiple causes that account for your sagging floor, but you should know that water and humidity often play a role. When you are planning to make repairs to your wooden framing system, keep in mind these may not be the only costs to consider.
Water around a foundation can cause settling or sinking; if you suspect this is an issue, we have a detailed guide to foundation repairs for you. You may need treatment for mold to restore good air quality to your home. You may also need to add a water drainage system to prevent the problem from recurring in the future- not only in the repaired sections, but throughout the basement or crawl space for prevention.
This photo was taken by an Acculevel project advisor; the crawl space is only 12 inches tall, so he was unable to conduct an inspection.
If you have a crawl space under your home, you will need to check the access dimensions. People and repair equipment need at least 18 inches of clearance. We have more information on how to find and measure your crawl space access in another blog.
Sill Plate Repairs
If your floor is sloping towards an outside wall and the foundation has not moved, this indicates that your sill plate is compromised. The sill plate is the piece directly on top of your concrete foundation, and it has to be replaced if faulty. To replace the sill plate, jacks are installed to temporarily hold up the floor joists, until the damage sill is removed and replaced. Costs for sill plate repairs are $100-$110 per linear foot.
Floor Joist Repairs
When the floor drops, dips or slopes it often means you have failing joists. Because the joists rest on the sill plate, water damage often spreads from sill plate to joist. Another common issue – especially in older homes- is notched joists. Older homes often have updated plumbing or HVAC systems installed; contractors sometimes cut sections out of joists to make room for new ductwork or pipes.
These notches weaken the joists and cause them to crack, split, or fail. Sagging joists need to be sistered to be repaired; removing the joists entirely would cause damage to the subfloor, and possibly to your flooring itself. When a joist is sistered, a healthy board is run parallel and attached to the faulty one, to transfer the load. Sistering floor joists costs $12-$14 per foot.
Illustration of a typical structural wood framing system, courtesy of NCSU.
Band Board or Rim Joist Repairs
Band boards- also called band joists or rim joists- are the wooden piece that sits on top of the sill plate. It protects the ends of the floor joists and helps support your home’s outside walls. Like the sill plate, the band board can be exposed directly to the outside air which increases the odds of it being damaged by humidity. Like floor joists, the best method for repairing band board is by sistering. Sistering band board or rim joists is $40-45 per foot.
This picture was taken by an Acculevel crew member after a routine installation. The sill plate has been replaced, and damaged joists have been sistered.
Center Beam Repairs
The most common complaint we receive is that the floor sags towards the middle of the home. This indicates that the center beam is failing in some way. In some instances, there are shims that have compressed and need to be replaced. Acculevel uses steel shims that will not compress and increase the surface of the bearing load. Installing or replacing shims is $105 per column.
If any of the support columns under the center beam have failed and need to be replaced, adjustable steel jacks can be installed. Likewise, if there are an insufficient number of supports currently installed, additional jacks can be added to better divide the load and increase the bearing area. Additional steel jack installations cost between $190-210.
This picture was taken by an Acculevel crew member during a routine installation. An adjustable steel jack has been installed in a crawl space, to support an existing beam.
If the center beam has cracked, split, or failed entirely, the best option is to replace it with a steel beam. Much like replacing a sill plate, jacks are used to temporarily hold the joists in place. Once those are secured, the damaged wood is removed and replaced with steel. Beam replacement is $260-$275 per foot, depending on the number (if any) of additional supports that are needed.
Support Column Repairs
If your floor sags in one specific area, this is possibly due to notched joists or beams. (Please refer to the earlier section on Floor Joist Repairs for more information.) If this is the case, sister joists or sections of steel beam can be installed to remedy the issue.
Frequently, a sagging floor in a localized area is caused by a damaged support column. If a wooden or concrete support is weakening or failing, it can be replaced by one or more jacks. Steel jack installations cost between $525-575.
The Cost to Repair a Sagging Floor
In the process of covering this topic, we’ve thrown a lot of terms and repair types at you. This is not done to confuse or overwhelm you, but to provide a detailed and thorough examination of the possibilities. While the average repair cost is $5900, there are a wide range of causes, and multiple components to evaluate. This is an area where even experienced DIY fans should defer to the judgment of an experienced and qualified foundation expert.
How Can I Find Help to Fix My Sagging Floor?
Find an experienced local foundation company, and make an appointment. Before you sign a contract for any service, you should always verify the company is reputable, insured, and accredited by the Better Business Bureau.
If you live in Indiana or the surrounding states, contact Acculevel. If you have noticed sloping or sagging floors, you can request a free estimate. An experienced project advisor will evaluate your foundation and recommend the best course of action for you, to keep your home strong and healthy for years to come.
We have also created a free tool that any homeowner can use to see what could be causing problems in your home and how to fix it. Identify problems, explore solutions, and get advice on how and when to take action with our Symptom Checker.