Sagging Floors

Sagging Floors

Sagging Floors

Sagging floors are often caused by moisture or water damage. Moisture causes wood to expand and contract more than other materials. As a result, floors may start to bow up or down. To prevent this problem, dry out your home before installing new flooring.

In addition to strengthening existing framing members, it is also possible to add new structural components using engineered materials. These include but are not limited to steel beams, trusses, and I-beams.

Sagging floors are often caused by poor construction or deterioration. Common causes include improper installation, lack of support beams, uneven subflooring, and improperly installed joists. There are many ways to remedy the problem including replacing existing joist hangers, installing new joists, using shims under the subfloor, and adding additional supports.

In order to reinforce existing floor joists or roof beams, you need to know how much force each member needs to withstand before failing. You also need to know what kind of forces cause damage to your structure. For example, if you’re building a house, you’ll want to make sure the foundation is strong enough to handle any potential earth movement.


Sagging floors result from failing floor joists in the crawl space underneath your house. These problems can result from open crawl space vents or doors, excessive moisture and humidity, and wet, rotting wood.

If you’re starting to see your floors sagging, you probably know it’s important to fix them. Sagging floors are an annoyance and an eyesore, but they can also be dangerous.

A sagging floor typically implies a sagging floor joist underneath it. These floor joists are sagging for a reason, and if you don’t tackle the underlying problem, you’re setting your home up for danger. You need to make sure you tackle the problem lying behind your sagging floors.

Sagging floors can indicate there’s damaged wood under your flooring, that one of your supports is deteriorating, or that there are problems with the foundations. Here are some other signs that you’ve got issues with your surface and how to fix sagging floor joists before it’s too late. 

Any crawl space home built atop clay soil can suffer from soil movement that adversely affects the foundation. Clay soils expand when saturated with excessive water and then contract when they dry. This continual swelling and shrinking exerts pressure on the foundation, which in turn can cause the piers and support posts to move, resulting in sagging floor joists. This leads to sagging floors and damaged flooring.

Unevenly spaced support pillars can also cause floor joists to sag. When the support pillars are not spaced correctly, the floor joists try to compensate causing the floor to sag and gaps to appear between the floor and wall or baseboards.

Types Of Properties With Sagging Floors

Which Homes Have Sagging Floors?

If you own an old home there is a good chance you have soft or sagging floors because of how the house was constructed. Most old homes with sagging floors were not built on the modern concrete foundation, they are sitting on dirt. If the floor pitches towards the center or stairs, it can be an indication that the house was built on dirt. This is because the house has been settling further down over time.

As a home seller, you are already going to be carefully inspecting your home but those little things that you’ve forgotten about over time are a big deal when selling. Owners of old homes might learn to experience springy or slanting floors as part of the charm, but they are signs of structural damage.

As a home buyer, look at whether the floors pitch at all or take a piece of string to test the floor’s deflection. Make sure the home inspection includes a report of the foundation and joist health. You don’t want to get stuck with a sagging home to fix after you’ve just spent your savings on an otherwise beautiful home.

Symptoms Of Sagging Floors

Primarily, when you start noticing the gradual slanting of your house to one side, then your floor is sinking. However, there are a few other silent indicators of sinking floors that our experts say homeowners don’t notice or ignore them. For instance, when you notice your doors or windows being jammed, you should know that you have sinking foundation problems affecting your floor.

Foundation cracks in your basement and on the walls of your living room are still indicators of a sinking wall. Moreover, if you notice water puddles collecting around the base of your home, it also indicates that your house is sinking. Therefore, when you notice things going wrong regarding your house, look into it because it could be an indicator of something worse.

If the floor feels springy and spongy when you walk, the subfloor might not be completely attached. Another reason for a soft floor could be from overextended joists; meaning the joists holding the house up are too long and not supported enough.

Pay special attention to the joists supporting your house, if the joists are wood posts in the dirt or with concrete poured around the base, then there is a good chance the joists are rotted. To test this just stick a screwdriver into the post at the floor line. If it feels mushy and nasty those will definitely need to be replaced.

It might seem obvious to spot an uneven floor , but there are other things to look out for. Some of the common indicators that you have sagging floor joists include:

Cracks or Crumbling on the Walls Inside the House

Sagging floor joists can also cause issues for your walls. Look out for cracks or fissures in the corners and joints.

Windows and Doors Problems

All of your windows and doors should fit perfectly inside your house. But it’s a different story when you have a sagging floor. They will either become too loose that it feels like they’ll rip off the walls or too tight that it takes more effort to open and close them.

Very Large Joist Spans

Beams in older homes were initially spaced further apart. Thankfully, today’s building codes have changed the spacing requirements. But if you’re in an older house, then the larger spans between the beams and the long floor joists may be the reason why your floor is sagging.

If a floor seems generally weak despite having adequately thick subflooring, it’s likely that the joists are undersized. Check your local building codes, but generally, joists should use the following guidelines if they are spaced 16 inches apart. If your joists are indeed too small, see some of the methods below to firm them up.

Spacings To Avoid Sagging FloorsYellow Pine,
Douglas Fir
Hemlock, Spruce
 Western red cedar,
Eastern white pine
Dimensional Lumber SizingSpacing at 16″ on centerSpacing at 24″ on center Spacing at 16″ on center Spacing at 24″ on center Spacing at 16″ on center Spacing at 24″ on center
2×69′ 9″8′ 3″8′ 8″7′ 6″7′ 6″6′ 3″
2×812′ 8″10′ 8″11′ 0″10′ 2″10′ 5″8′ 6″
2×1016′ 0″13′ 0″14′ 6″12′ 4″12′ 9″10′ 5″
2×1218′ 6″15′ 0″17′ 6″14′ 4″14′ 9″13′ 0″
Joist SizeMaximum Joist Span To Avoid Sagging Floors
 2″ x 6″ 8’6″
 2″ by 8″ 11′
 2″ by 10″ 14′
 2″ by 12″ 17′

Sloping Floors

Some homes have floors that are very uneven. Often times this is caused by long spans, moisture, and settlement. If the floors in a home are not even, there is a good chance the floor joists are not supporting as they should.

Bouncy Floors

If you hear rattling every time you walk around a corner, the floors are probably getting by with minimal support. Bouncy floors cause furniture and other items to shake and vibrate due to inadequate support. If the floors do not feel firm, that’s a sign the floor joists need more support.

How to Inspect Your Home When Your Floors Are Sagging

If you want to confirm your suspicions about your uneven floor, there are ways that you can investigate your floor joists. But you do need to know what you’re looking out for.

The easiest way to check is if you have a basement. Take a good look at the basement support beams and posts that meet the floor.

Crawl spaces are not as easy to inspect. You will want to wear protective clothing like a Tyvek suit, gloves, a headlight (or flashlight) and potentially a respirator.

While you’re in the basement or crawlspace, if you notice that it’s continuously damp, then it could be a hive for insects that love to destroy floor joists . Powderpost Beetles can turn them into swiss cheese by chewing through them. Carpenter Ants and Termites can also do plenty of damage to floor joists, particularly in the Spring.

If you are able to inspect the floor joists directly, you’ll want to see if they have fungal growth, spans greater than 10′, proper support by the beams and piers, or excessive moisture.

What Causes the Living Room Floor to Sag?

faulty floor support structure design

Poor structural support is the most common cause of sagging floors. When your floor joists start to bend downwards due to pressure and weight of the overlying material, your floor will start sagging. The best way to fix sagging floor joists is by installing new support structures such as jacks. You should place each jack appropriately while minding the bearing weight and the strategic location of the joist.

The floor of each of your rooms has long joists, which are supported by a central beam, and the beam is supported by posts underneath. If the underneath posts develop problems such as rots, the beam might not offer sufficient support, making your floor start sagging. Additionally, the underneath posts may be too far apart, hence not supporting the beam, making your floor sink.

The initial design of your home has to be able to hold up the weight on top of it. Unfortunately, if the original design isn’t strong enough, you can end up with over spanned floor joists. That means the support columns are improperly spaced, causing the design to put too much weight on the floor joists underneath.

This poor design can reach through other parts of the home as well. A poor support design can itself cause gaps between walls and floors, squeaky floors, cracks in the drywall and a variety of other problems. Plus, you never know what other parts of the home suffer from the same poor design.

Long joist spans and poorly planned structural layouts cause more sagging floor joists than anything. If the beams are spaced too far apart, the long floor joists are probably stressed and bowing under the weight of the home and gravity.

In order to avoid sagging floor joists, you need to make sure your foundation is properly built. You also need to ensure that there are enough support beams placed between the joists. Otherwise, the floor joists may sag or bow under the weight of the house.

A crawl space repair professional, like Bay, can install strong foundations, steel structural jacks, and new custom beams to permanently stabilize the floors and walls in almost any area.

2. Moisture problem

Find out if the sagging of your floor is due to the moisture problem. If so, you should learn how to dry out your crawl space. You can fix the moisture issue by sealing the leaks from the outside elements and drying out the crawl space. Solving the moisture problem addresses the sagging problem.

3. Settlement weight

Your home is going to settle over the years; that’s a normal part of what happens to your home over time. However, if your home starts to settle unevenly or too quickly, you’ll start to notice problems like sagging floors, squeaky floors, and cracked bricks.

A sagging floor from home settling will cause bigger problems than just the floor. The settling can be very damaging to your foundation as a whole, especially if it’s settling more on one side than the other. It’s incredibly important to pay attention to the home settling issues you’re having, regardless of how “bad” it looks from the top.

In order to prevent settling, you must first determine what factors contribute to settlement. You should then take steps to minimize or eliminate these factors before building your home. For example, if you’re planning to place heavy furniture near the floor joists, you’ll need to be sure that the floor joists aren’t supporting any such furniture.

In typical construction, flooring settles toward the center of the home due to the fact that the perimeter walls are built over a deeper foundation than the interior walls. Support beams within this perimeter are typically supported by makeshift posts.

If your floor sags due to the settlement weight, you should install many jacks to support the massive weight. Depending on the extent of the occurrence, you can reinforce the foundation by use of push piers to keep the foundation stable and safe.

Settling in the foundation is a possible cause of your sinking floor. If your living room is at the center of your home and is placed on one side, it might be a cause for a sunk in floor.

Excess load

You may have a more massive load in your home than initially intended for your home design. If you have bought a lot of furniture or something more substantial like a piano or maybe you might have added an extra feature on your cabinet, it will add extra weight, which will make your floor to sink.

Damage Of Wood

When the joists of your floor become old, they weaken and therefore make your floors to sag. Moreover, if they are exposed to high humidity for a long time, they may absorb moisture then rot, which makes them sag.

Wood tends to rot when it’s exposed to humid air and moist dirt. This can cause the joists to weaken and shift the support it’s supposed to give to the subfloor. It’s essential for you to know how your house was built so that you understand how you’re going to repair the sagging floor joists.

Lack Of Waterproofing

Sagging floor joists can also happen if your crawl space or basement isn’t properly waterproofed. A proper waterproofing job should avoid and prevent both standing water and humidity in the area. Either one of these things can cause serious problems along the underside of your home.

If your home doesn’t have adequate waterproofing in the crawl space, you may start to see sagging floor joists because of serious rotting and molding problems. Those problems with moisture can also reach up to the rest of your home, causing molding in the home walls, cracking due to humidity, and more.

Cosmetic Issues

This might not be high on your personal list, but it’s an important thing to note nonetheless. It’s true that sagging floors are a pretty big cosmetic eyesore, which can be annoying.

Not only is the floor itself a cosmetic problem, but it can also wreak havoc on your internal decorating. If a sagging floor is sagging too far, you may have problems with putting up chairs, tables, bookcases, and other décor because it’s impossible for your floor to hold these things up.

Should I Fix Sagging Floors?

An uneven floor can often be just the beginning of problems to occur with your home. If the reasons for the issues with your floor joists are a wet crawl space, then you can expect more troubles to come.

When a crawl space isn’t sealed off properly and protected from moisture, it can damage the floor joists, rot the wood, attract insects and pests, grow mold and bacteria looking to sell your house , then it will hit your hip pocket harder. Realtors must disclose to potential buyers that the foundation of a home is weak, damaged, or has sagging floors. This can potentially drop the value of your home by up to 20% if you’re looking to sell.

Sagging Floor Repair

The most important reason you can’t just go in and sister the joint yourself is that it might not fix the problem. That might be an effective fix if the floor joist being unsupported is truly the only problem, but chances are, it’s not. If you’re dealing with moisture in your crawl space, a structure that simply isn’t sound, or poor planning throughout the home, your sagging floor joists are just symptoms of a bigger problem. You need to handle those problems before you handle the sagging floors. 

Repairing sagging floor joists may be done by using a variety of techniques. Depending on the situation, some of the most popular methods of fixing sagging floor joists involve:


The first step in fixing your sinking floor repair is having it inspected by a professional. Structural engineers will diagnose the foundation problems and tell you precisely what should be done. After the problem diagnosis, our foundation specialist will take over. Our experts use several ways to fix a sinking foundation, and each one of them is efficient for different situations.


The first step to locate the area of sag for easy rectification is troubleshooting. Saggy floors are noticeable, but you will still take measurements from the floor to the ceiling across the entire floor. The data collected will help you to know precisely the points of sag and decide on the suitable method to fix it. Even though the standard building codes allow for a certain degree of sinking, you should repair noticeable sags.

Alternatively, you can use carpenter’s level placed on a four-feet 2-by-2-inch board to check the extent of the sag. However, you can also use a small rolling ball or bottle on the surface and check on the direction as well as the speed of rolling. For massive sags, the object will move faster.

Underfloor examination

You should get under the floor with a bright flash-light to examine the floor from below. Check on breakages which may appear on the joists. It is important to note that joists with their crown side facing down will always tend to sag as time goes by. To fix the problem, you will have to obtain some temporary and adjustable columns to reinforce the joists.

Footings and post support

Make a concrete footing to give support to the joists and hold them back. For your concrete foundations to be firm, you should dig down 2 feet deep and insert your footing support pillar. The depth, width, and height of the footings will depend on the standard building codes and the overlying load. Also, you can add a support beam with columns remaining in place. Ensure you level the ground before installing the bricks and support piers.

Install Girders And Sister Joists

Sistering is when an identical piece of wood gets fastened to the floor joist. A sister joist is just an additional joist that pairs up with the original one to help carry the load.

This provides extra support and is better secured compared to ‘scabbing’, which can be inadequate.

If you suspect a sagging floor joist to be the cause of your problem, be careful about driving additional screws through the flooring. This sometimes has the unfortunate effect of pulling the floorboards down, making the finish flooring dip instead of becoming stronger.

Sagging or bouncy floors are often caused by a weak floor joist that has sagged under the load of people walking on the floor above. If the issue is caused by just one or two joists, you can probably handle it yourself by attaching a “sister joist” to the original ones. If multiple joists are involved, call in a carpenter because greater structural support might be needed.

If the underside of the floor is accessible from the basement, that is ideal. But many 1st story floors will require it to be approached from a crawl space beneath the house. Either way, you’ll want to access the subflooring to measure before cutting sister joists to length.

Cut the sister out of 2-by lumber, ideally at least 6 feet long. It can be the same width as the original joist, but it’s easier to fit it into place if it’s narrower, as shown in the illustration above.

Press it up against the bottom of the floor and hold it temporarily in place by wedging vertical 2-by-4 supports under it as shown. Drive pairs of 3-inch wood screws every 8 inches or so to secure the sister to the original joist.

Pros: In many cases sistering can be the most effective way to fix floors with minor deflection. By installing sister joists, you are effectively doubling or tripling the rigidity of the affected area.

Cons: Can only be accomplished if the under floor area is not crowded with plumbing pipes, electrical cables, vents, ducts, or other obstructions.

To repair a cracked joist, attach plates of reinforcing metal gussets or panels of 3/4-inch plywood. Use screws that are long enough to penetrate most of the width of the joists without poking through on the back side.

It is possible and preferable to strengthen or repair existing framing members, like the floor joists, by adding reinforcing material.

The best option is sistering, bolting identical lumber to the existing member.

For even better stability you can sister with a flitch plate, a 1/4″ to 1/2″ piece of steel or plywood.

Using two flitch plates to repair localized damage is also a good idea.

Sometimes these repairs aren’t sufficient, so you might consider shoring up joists or beams that were cut, drilled, or notched for pipes, wires, and ducts because the improperly drilled ones can lead to sagging as well.

Install a new sister joist to support the old beams and provide the strength needed. Alternatively, you can add a girder perpendicular to the sagging beam but underneath the floor and beam. Ensure you mark the crown of the beam to avoid future sag as a result of the beam being upside-down. Always install a joist with its high side facing up.

Sistering a joint can sound like an easy fix for a sagging floor crawl space. After all, you just have to place something underneath the sagging areas in the crawl space, right? Is it really that difficult to accomplish?

The thing is, it’s not as easy as it may look at first. In fact, you need to make sure you’re sistering the joint at the right place if you want to be effective in leveling sagging floor joists.

The above methods are useful on to fix sagging floors in the old house.  If you are are not sure of how to undertake the activity, you’d better hire qualified and skilled personnel to help fix your sagging floor. However, avoid using green wood as it may dry and shrink, thus making your floor uneven. 

High-pressure grouting

This method works by inserting grout into the unstable soil, to improve its composition or raise the structure of your house.

Install Blocking Pieces Between Pairs Of Joists To Mitigate Sagging Floors

This process may not resolve completely the issue of sagging floors, depending on the level of bounciness that the floor had. While this process is easy to implement, I still recommend sistering floor joists with strong joists, not simply with some 2×6, as the generally preferred methodology to fix sagging floors.

To fix sagging floors while strengthening the entire surface, install blocking between pairs of joists. From 2-by stock that is the same width as the joists, cut pieces so they fit snugly perpendicular to the joists

Again, you’ll need to access the underside of the floor either from the basement or a crawl space. Carefully measure the distance between joists, numbering them if necessary when distances vary.

Tap each block into place between the joists, using a hammer. Offset or stagger each block from the one next to it by 1 1/2 inches to make nailing or screwing into the ends easy as shown below. Use 3-inch screws or 16d nails to secure the blocking to the joists to support the floor above.

Load-bearing piers

They can be used to raise the foundation of your home while at the same time, stabilizing it. The use of load-bearing piers is exceptionally beneficial in raising your sunk in the floor. This is because they offer a permanent solution to sinking floor problems. Moreover, they are also quite affordable, making them economical to use.

Helical piers

They are mostly used where other piers cannot be used. They are also beneficial because they also provide a permanent solution to your foundation sinking problems. Also, they are efficient, where a high water table is present.

Addition Of A Reinforcing Metal Bridge

Depending upon the conditions, it is possible to strengthen or repair existing framing members, such as floor joists or roof rafters, by adding reinforcing material. Sandwiching the member on either side with plywood is sometimes worthwhile, but the plywood must be installed correctly for greatest strength.

Steel bridging doesn’t add as much strength as blocking, but it does prevent joists from twisting. It provides a measure of reinforcement and cuts down on squeaks, too—and it’s is easier to install than blocking.

Purchase steel bridging pieces that are made to fit the spaces between your joists, typically 14 1/2 inches long. Wedge each piece tightly into position, and drive a 1 1/2-inch nail or screw through each hole. Where the spacing between joists is less than the standard 14 1/2 inches, use wooden blocking instead.

Pros: Easy installation (and removal if you don’t get the desired result). Materials are cheap.

Cons: Will have varied results based on your flooring materials and the severity of the problem.

Correcting Deflection Through Beam Replacement

One of the biggest issues with structural damage is that the conditions can affect all of the wooden framing under the house. Any structural beams that are damaged or sagging should be replaced or supported.

In most cases, to fix sagging floors you will need to use jacks and support beams. This can be a tricky process to try alone so consider hiring a professional foundation repair team.

New concrete pads with footings should be put down over existing dirt floors.

Install temporary jack posts and support beams, then place permanent posts and beams over the new footings.

Create a waterproof barrier between the post and the footing by placing wood posts on metal post supports.

A great way to check your improved floor and amount of deflection is to stretch a taut string across the floor.

Adding Layers Of Subflooring

Another way to firm-up a floor is to add more than one layer of subflooring that is 1/2 inch or thicker. What you’ll use for this usually depends on the finish flooring. Plywood is best for strength, but cement backerboard is better if you are installing ceramic or stone tile, and 1/4-inch underlayment works well for vinyl tiles or sheet flooring.

Increase the strength by using plenty of fasteners. Drive long screws every 6 inches into joists, and drive shorter screws (just long enough to penetrate all the way through the subfloor) in a grid every 8 inches between the joists. Fixing plywood in flooring adhesive will also add firmness.

Atlas resistance piers

This uses hydraulic pressure to help push piers into the soil. They depend on the weight of your house, to push the piers down. We use this in places where bedrock is shallow.

Soundproofing Against Floor Squeaks

You can solve some floor squeaks simply by driving in additional nails or screws. Of course, this is not a good solution if you’re dealing with a hardwood floor or some other flooring where the fasteners would be visible.

Installing Wooden Shims

If a joist sags so that you can see a space between the subfloor and the joist, buy a few wooden shims. Gently tap them into the gap with a hammer (hitting them too hard may cause the floor to rise). Tap-in a shim every 2 to 3 inches. After you have inserted a group of shims, go back and gently tap each one to make sure they are all snug.

Pros: Materials are extremely cheap. Easy to install and remove. Can be very effective for smaller, targeted areas of bowing floors.

Cons: If too much pressure is applied too quickly, you can run the risk of damaging the flooring surface above. So make small adjustments, and consider increasing the upward pressure over the course of a few days.

How to Fix Sagging Floors

We show you how to fix sagging floors by understanding the common structural shortcomings that cause floors to sag and what to do about them.

One of the most common complaints of old-house owners is sagging floors. In my own house, for example, every floor pitches toward the center stairwell. Although generally only an annoyance, sagging floors can be an indication of worsening problems. Here’s a quick review of the most common problems and a few of the typical remedies.

Depending upon the conditions, it is possible to strengthen or repair existing framing members, such as floor joists or roof rafters, by adding reinforcing material.

What Causes Sagging Floors in Older Homes

Typically, floors settle near the center of the house because the perimeter walls are constructed over a sound, deep foundation and settle very little. Major support beams within this perimeter, though, are often supported by makeshift posts.

How to Inspect Your Home When Your Floors are Sloping

Inspect Support Beams: If your house is built over a basement, first inspect all of the basement support beams and posts where they meet the floor. Be suspicious of wood posts set on dirt floors or wood posts with concrete poured around the post bases. As the posts slowly rot and melt into the floor, the house settles accordingly, bottom to top. As a test, firmly push a metal probe or screwdriver into the post at the floor line. If this area is mushy, punky, or rotten, you may have found your problem.

Inspect Floor Joists: Also look for floor joists that have been cut improperly to install pipes, wiring, or HVAC ducts.

Look for Insect Damage and Moisture: If you’ve had a chronically damp basement or crawlspace, look for indications of insect damage to structural members. Powderpost beetles leave joists and beams riddled with small holes, carpenter ants are usually apparent at the first sign of warm weather in the spring, and termites usually leave telltale mud tunnels on foundations and posts. Then solve moisture problems around and under the house and repair deteriorated or compromised structural members.

Support posts should not sit on dirt floors, but instead be upgraded to concrete pads with footings that spread the load.

Improper holes and notches from alterations and running service lines are a major source of weakened joists. Generally there should never be any cuts or penetrations in the middle third of any joist, or anywhere along the bottom of the joist. Notches at the end of a joist should not exceed 1/4 of the joist depth. Center notches (B) should not exceed 1/6 of the joist depth. Holes should be a minimum of 2″ in from the top or bottom of the joist, and no larger than 1/3 the depth of the joist.

Three Ways to Fix a Sagging or Sloping Floor

Sistering: A better option is sistering, where identical lumber is bolted to the member.

Sistering with a Flitch Plate: Better still is sistering with a flitch plate, a 1/4″ to 1/2″ piece of steel or plywood. Two flitch plates may also be used to repair localized damage.

Where these repairs are not sufficient, also consider shoring up joists or beams that were cut, drilled, or notched for pipes, wires, or ducts.

Stretch a string across the floor to evaluate the amount of deflection, then use it as a benchmark for improvement when jacking.

One of the good things about floor deflection is that it is repairable. The bad news is that it often takes a long time. The solution to sagging floors or the damaged sills and joist ends that contribute to them, often involves jacking. A common scenario is to install temporary jack posts and support beams, then permanent posts and beams over new footings. A taut string stretched across the floor will show the amount of deflection and improvement. Posts set on dirt floors should be upgraded to concrete pads with footings. Place wood posts on metal post supports to create a waterproof barrier between the post and the footing.

Jacking must proceed slowly; it took a long time for your floor to sink, so you can’t push it back up quickly without causing cracks and stress in the building. As with other structural repairs, jacking must also be done appropriately. You cannot simply put a screw jack under the lowest spot and start turning. Ideally, someone with experience will assess the problem and set up the posts and any necessary beams. You can then screw the jacks up a turn or two each month. Expect some cracked plaster along the way, and aim not for perfection, but simply stability and improvement. After all, if perfectly level floors and pristine walls were important to us, we wouldn’t live in old houses, would we?

You may want to contact a structural engineer before doing any work as a precaution.

Sagging Floor Costs

Have a sagging or sloping floor? This is a clear sign of structural problems. We’ll explain what types of repairs are needed and what they cost.

How much does it cost to fix sagging floors? A full pricing breakdown.

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. 

There is a  $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

The fact is, it’s never going to be cheaper to fix your sagging floor crawl space than it is right now. It’s only going to get more expensive as the problems mount and get worse. Instead of trying to save money by not fixing your sagging floor joists, you should actually fix them as soon as possible. If you tackle these problems early, you won’t have to deal with an even more substantial problem later, which will cost you many times more to handle.

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.

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.

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.

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.

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. Contractors use 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.

For repairs with adjustable jacks, please be aware that the floors will not immediately return to level. Jack adjustments are done in small increments over time; attempting to expedite this process can cause damage to your home. 

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 To Replace A Sagging Floor

How to Replace a Sinking Floor. A sinking floor is usually a sign that the floor has begun to rot out from the underside, meaning the joists or other elements of the subfloor have failed.

Removing the Existing Subfloor

You’ll need to rely on manual labor, prybars, crowbars and hammers to remove any existing flooring material, such as tile, wood or carpet. Use a circular saw with the depth set to the thickness of the plywood or particleboard subfloor and cut out the sunken sections to expose the joists.

Checking for Joist Damage

Inspect the joists to see which ones have failed and need to be replaced. Look for rotten wood, termite damage and water damage. The sunken sections will be easy to spot, but look for damage further along the joists — away from the obvious areas — so you can avoid potential issues down the road.

Removing Joists

Use a reciprocating saw to cut the bad sections of joists away. Cut into the good section of the joists at least 6 inches further up than any existing damage. That way, you will ensure that any rot or mold is completely removed and won’t affect the remaining joist material. This will clear the way for the new installation so you can build the floor up from scratch with new lumber.

Replacing Joists

Pick up some matching joist material from a home improvement store and then install it. Your goal is to overlap the new joist material with the existing joists by at least 12 inches, so that your new joist material spans the gap between the open areas where you cut the rotten wood out. Nail or screw the new joists onto the old joists where they overlap, and then install your new subfloor and your new finish material, such as carpet or tile.

Exceptions to the Rule

Sagging joists have already failed and are thus not supporting the floor any longer. As a general rule, you can replace any joists in the middle of a floor or area because they are not supporting the weight of a home. If you discover during your removal of the subfloor that the joist damage extends underneath a load-bearing wall, however, you will need to contact a structural engineer. Seek professional help to brace the wall while the joists are replaced.

Tripping Hazard In Sagging Floors

In some cases, a sunken floor can also be a tripping hazard. Your brain typically expects to be walking on stable ground, and if the ground slopes downward, you may end up tripping over it.

Of course, this is most difficult for elderly and disabled individuals who may have a difficult time walking even on stable surfaces. However, don’t make the mistake of assuming you won’t be impacted by it. You may end up tripping even on surfaces that don’t seem extremely uneven.

Leveling sagging floor joists can help with this problem. 

Always Fix Sagging Floors Before Selling

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BY M. Kogan

Hello, I am Marcio. I am an architect and designer, alma mater is Mackenzie. Retired in theory, but an architect never retires completely. Along with architectural projects, I am a filmmaker and have completed some short documentaries. Filmmaking and design are my passions. In HomeQN I write about home decoration and foundations. The goal is to teach homeowners to DYI as much as possible, and when this is not possible, enable them through knowledge, to evaluate service quotations and choose the best service technicians.

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