Home Foundation Repair Need To Fix A Sagging Floor? Costs Guide & Why You Should Not Delay Repair

Need To Fix A Sagging Floor? Costs Guide & Why You Should Not Delay Repair

fixing the sagging floor

Are you wondering what it will take to correct your sagging floor?

You have come to the right place!

In this Regional Foundation Repair guide, we cover common questions like:

  • What Is The Cost Of Fixing Sagging Floors?
  • What Usually Causes Floors To Sag?
  • Can You Delay Repairing Your Sagging Floor?
  • What Are The Methods For Fixing Sagging Floors?

And much more!

The floor of your home should provide a smooth, level, and steady surface for you and your family members to live on.

If there are ridges, slopes, or if the floor feels bouncy, this should be a cause for concern as it could indicate the presence of underlying problems.

So, if you’re concerned about the integrity of your home’s floors, keep reading to see whether you should contact a professional to address the issue!

Table of Contents

  1. What Is The Cost Of Fixing Sagging Floors?
  2. What Usually Causes Floors To Sag?
  3. Can This Type Of Repair Be Delayed?
  4. What Are The Methods For Fixing Sagging Floors?
  5. DIY: How To Fix Sagging Floors Yourself
  6. How To Save Money When Fixing Sagging Floors?

What Is The Cost Of Fixing Sagging Floors?

Various factors will determine how much your repair will cost, but the most important one is the type of foundation you have, as well as the types of flooring you have.

Cost For Concrete Slabs Floors

For concrete slabs, the repairs will either involve slab jacking or the use of piers. For mudjacking, the average cost will be $3 – $6 per square foot, whereas poly jacking will cost between $6.70 to $16.70 per square foot.

To put it in perspective, repairing a 1,500 square foot by mudjacking will cost between $4,500 and $9,000, whereas poly jacking will cost between $10,000 and $25,000.

The cost of installing a pier is between $1500 and $2500, which places the cost of repairing a 1,500-foot floor between $12,000 and $50,000.

Cost For Crawl Spaces and Basement Floors

For houses with crawl space and basement foundations, problems within the joists and support beams are usually the main cause of sagging. The cost of these repairs will depend on the method used and the extent of the damage.

Below is a simple breakdown of the costs based on the method of repair:

  • Sill plate repairs will cost between $95 and $100 per foot
  • Floor joist sistering repairs will cost between $11 and $13 per foot
  • Rim joist or band board repairs will cost an average of $38 – $42 per foot
  • Replacing worn-out shims will cost you $100 per column
  • Steel jack installation to replace support columns will cost about $175 – $200 each
  • Replacing the center beam will cost between $24 – $260 per foot

Of course, the actual price of the repair will depend on other factors such as accessibility of your repair area and the condition of your floor. The only way to be sure is to fill the form and schedule an inspection with one of our experts.

What Usually Causes Floors To Sag?

Ultimately, there are many factors that can cause a floor to sag and each one has its own unique causes and ideal methods of repair.

So how do you identify what’s causing your floors to sag?

Read through the most common causes below and if any of these seem like a possibility for you, please reach out to one of our experts to prevent your floors from sagging even more!

Moisture and Humidity

Is there water in your crawl space or around your foundation wall? Then this may be the cause of your sagging floors, especially for basement or crawl space foundations where wood is part of the construction.

When water gets into the wood beams, girders, sill plates, or floor joists, it will make them vulnerable to wood rot.

This is why you should take every measure to keep your crawl space and basement dry. Please note that there does not have to be standing water for your foundation to suffer structural damage.

Due to its high porosity, wood in a humid environment will absorb moisture and suffer serious water damage.

Another effect of excessive moisture near your foundation is that it facilitates the growth of mold and mildew. When these grow on your support beams and foundation walls, they will weaken them and could result in them buckling under the pressure, causing the floors above to sag.

Insects And Other Creatures

Insects are also common perpetrators of foundation problems.

While they cannot damage foundations made of concrete or brick, they will find their way into the wooden parts of the foundation. Here, they will eat along the wood grains, leaving behind mazes made of mud, saliva, and feces.

If their feasting on the wooden structural components does not destroy your foundation’s support, the rot resulting from the mud will do the job.

Foundation Settling Or Sinking

Foundation settling is mainly caused by changes in the soil underlying your home.

For new homes, foundation settling can be natural and will not always result in any major problems. However, factors like moisture and living organisms will accelerate the sinking process and cause more adverse effects that will be hard to miss.

These effects of foundation sinking include but are not limited to:

  • Cracks in your floor and walls
  • Doors and windows refusing to close and open
  • Walls falling out of plumb
  • Nails popping through the walls
  • Sagging or uneven floors and porches
cracks in foundation walls can be an effect of foundation sinking

Where foundation settling is the cause of sagging, lifting it back to the original position should resolve the issue.

However, before jacking up your sloping floors, you should ensure you have solved the initial cause of the sinking to prevent the problem from recurring. If a wet crawl space was the cause, ensure you first dry and waterproof it to keep all moisture away.

Poor Support Structure Design

When building your foundation, your contractor should follow all building codes to prevent any future structural issues.

For instance, the main support beam should be sized accordingly and supported every few feet by posts as per the weight requirement of your home.

In instances where the support beam is not strong enough or where the support posts are too far apart, the weight of your home will be too much for the floor joists to bear.

As a result, the floor areas between the support posts could sag or could even collapse. If your floor slopes towards somewhere at the center of your home, the cause could be from failing support structures.

Human Error

For most homes, the installation or retrofitting of electric, HVAC, or plumbing products is done in the crawl spaces and basements.

Sometimes, making room for the pipes and vents will require contractors to notch or cut out some parts of the joists, support poles, or even the main support beams. If not done carefully, such notches will cause weaknesses in the flooring, which could eventually result in sagging or sinking.

This is why you should be careful when hiring contractors to repair or update your home.

At Regional Foundation Repair, our experienced specialists will examine all aspects of your home before suggesting or applying a solution, ensuring no further damages will result from the repairs.

Can This Type Of Repair Be Delayed?

As tempting as it is to brush away a sagging floor as a minor inconvenience, you should get it fixed as soon as possible.

Sagging floors may not create a falling hazard or cause your home to collapse, but they are an indication of underlying structural problems that you should have looked at – especially if you live in areas that are prone to earthquakes, tornados, or mudslides.

The more you delay the repairs, the more the damage will spread and the more difficult it will be to resolve the problem.

The amount of slope also determines how serious the problem is and the extent of the repairs required. As a general rule:

  • Slopes that are ½ to 1 inch or more in twenty feet are a cause for some concern
  • Slopes over 1½ inches twenty feet are probably serious and should be investigated immediately
  • Slopes that are more than 2 or 3 inches in twenty feet are incredibly serious and should be resolved immediately

What Are The Methods For Fixing Sagging Floors?

There are many methods of repairing sagging floors and the most appropriate one for your situation will depend on factors such as the type of floor, the type of foundation, and the extent of the damage, among other factors.

Some of the common repair methods used include:

Slab Jacking

Slab jacking is applicable where the cause of sagging is a shifting or sinking foundation slab. It involves injecting material under the sunken foundation slab to lift it back to its original elevation and offer the support needed to prevent further sinking.

When a mixture of mud, water, and cement is used, the process is known as mudjacking, whereas poly jacking involves injecting polyurethane foam in place of mud slurry.

Before slab jacking your floor, be sure to first address what caused your foundation slab to sink.

For instance, if moisture problems in the underlying soils caused excessive shrinking, you could use french drains to channel the water away before lifting your floor, or else the problem will recur.


One shortcoming of slab jacking is that it is not suitable for lifting heavy structures or those with extensive foundation sinking. For these, you may need more extensive methods such as piering.

But what is piering?

Piering involves installing piers or beams under the sinking foundation, penetrating the weak topsoil to rest on the more solid load-bearing soil level.

The piers are then used to jack up and support the foundation to its original elevation, preventing further settling. It is especially applicable where the cause of the sinking is weak topsoil that compresses under the weight of the home.

There are three main types of piers, namely:

  • Helical piers
  • Steel push piers
  • Concrete piers

Helical piers are like large screws drilled into the load-bearing soil using a hydraulic torque motor, with helical plates on their surface offering more support.

Push piers, on the other hand, are giant steel pipes that leverage the weight of the structure to push them into the load-bearing strata.

With concrete foundation piers, a hole is first drilled under the house, then filled with concrete to the desired height, and left to cure. It is more labor-intensive and messy than the other methods and will take longer since it requires time to cure; typically a week.

Support Posts And Footings

If the sagging of your floor is concentrated in one specific area, a corresponding support post has likely failed. This can be corrected by adding or replacing support posts and footings after jacking up the floor.

Adding support posts can also be used as a preventative measure if an inspector notes that the ones present were installed too far apart.

Support posts can either be made of wood, concrete, or steel piers. With a wooden support, a concrete footing should be used to prevent it from sinking, and to protect it from elements such as moisture and insects.

Concrete support beams could either be pre-made or could be made on-site. Steel beams are the most efficient support posts you could use.

Reinforcing With Sister Joists

In situations where the joists are failing either due to structural damage or the weight of the home, sister joists can be used to provide additional support.

So, what exactly are sister joints (a.k.a sistering)?

Sistering can either be done using identical wood or using a flitch plate either made of plywood or steel where more support is required.

After jacking up the floor to the desired height, the sister joists are screwed alongside the sagging floor joists to increase their load-bearing capacity to prevent further sagging.

Although this may seem obvious by now, the importance of first resolving the underlying problem cannot be overstated.

If the reason the joists failed was the effects of moisture, insects, or inadequate support posts, you should first address them, or the sister joists will only hold for a while before failing too.

Adding Another Flooring Layer

Another way to repair sagging floors is by adding another floor layer on top of the existing one. To install a new floor layer, you will first need to add an underlayment, where the type used depends on the final floor covering you will use.

For a tile or stone floor, you will require a cement backer board as underlayment. A hardwood floor will utilize a plywood underlayment.

You should ensure that your joists and support beams can handle the increased weight from the new subfloor. If necessary, you can reinforce them by adding sister joists, adjustable columns, and support beams as required.

DIY: How To Fix Sagging Floors Yourself

If you are a DIY enthusiast or handyman, you may choose to repair your sagging floor yourself. This is possible if you can pinpoint the cause of the sagging to a certain part of the flooring, and where the repair method does not require specialist knowledge or tools.

Below is a step by step DIY guide for fixing sagging floors caused by failing floor joists:

Equipment/ Tools

  • House jacks
  • Cordless drill driver
  • Adjustable steel columns
  • House Jacks
  • Carpenter’s glue
  • Auger bits
  • Bubble level
  • Framing hammer
  • Electric miter saw
  • Carpenter’s pencil
  • Tape measure


  • Bolts, nuts, screws and washers
  • Matching joists for sistering
floor joists in the basement

Step 1: Jack up the floor

The first step is lifting the sagged joists to return them to the desired height. You can do this by placing house jacks below the target joist or in strategic points if various joists are compromised.

You should then jack up the floor slow by slow, about 1½ inches per month. Forcing the floor up at once could create other problems such as cracking drywall, cracking floor, damage to windows and doors, among others.

Step 2: Place the adjustable steel columns

While continuing to jack the floor up an inch at a time, secure the base of the adjustable steel columns to the joists and the basement floor.

Step 3: Measure and cut out the sister joists

The next step is to measure and cut the sister joists out of 2-by lumber, preferably longer than 6 feet. The width can be the same as the original joist, but it can be wider or narrower. While narrower sister joists are easier to fix, wider ones will provide more support.

Step 4: Sister the joints

It is now time to join the newly cut joist to the failing one. Apply an adequate amount of carpenter’s glue on the sagging floor joist and press the new one against it. You can hold it in place using vertical wedges.

Using the drill driver, drive pairs of 3-inch wood screws at intervals of about 8 inches to securely join the new joist to the original one.

Step 5: Install support beams

After the sister joists are firmly attached, you can install support beams and connect them to a concrete or steel footing on the basement or crawl space floor.

Step 6: Remove the house jacks

Now that the floor has been restored to the desired height and the joists reinforced and supported, you can remove the house jacks and clean up your basement or crawl space.

How To Save Money When Fixing Sagging Floors?

Construction repairs are usually a costly affair, and it is therefore understandable that most homeowners look for ways to save money.

But are there options that can get the job done for less?

Here are some ways you can keep your sagging repair costs low.

A Fix In Time Saves Nine

When a support beam or joist fails, the pressure is distributed to the other support structures, and they will most likely fail too.

It is, therefore, wise to have the issue resolved as soon as you see the first signs of trouble to prevent the damage from spreading and increasing the costs of repair.

Let A Professional Handle It

It may seem cheaper to handle the repairs by yourself or to employ the services of inexperienced people. However, if you apply the repair incorrectly or misdiagnose the cause of the issue, the problem will only get worse (and cost more) in the long run.

It is, therefore, wiser to get the help of qualified and experienced professionals, even if they come at an additional cost.

At Regional Foundation Repair, we have a team of highly qualified foundation repair experts who guarantee stellar, long-lasting, and affordable services to help homeowners make their homes the safe and comfortable havens they desire.

Leave a Comment