4 Steps To Fix A Sagging Floor Joist

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The floors are one of the first things I look at whenever I conduct a home inspection. If you use stylish floor decor, your home’s interior will significantly improve. However, over time your beautiful floor might start to become unleveled and sag. But worry not because there are ways to fix a sagging floor joist.

You can fix a sagging floor joist by troubleshooting the problem and implementing corrective measures such as:

  • use a foundation jack to lift the floor structure and add a masonry support pier adding a support pier.
  • sister a new floor joist along side a damaged floor joist.
  • replace damaged girders with new girders in the floor.

Some of the common causes of floor sagging include settlement weight and moisture problems.

But I’m sure you want to know more than just the reason why floor joists sag.

In this article, we’ll explore ways of fixing a sagging floor joist. Read on!

How Do You Fix A Sagging Floor Joist?

It won’t be challenging to identify a sagging floor joist. After you have identified a sagging joist, you should take the appropriate steps to fix it. Follow the steps below to fix sagging floors in your house:

1. Troubleshoot

The easiest way to identify a sag in your home for immediate rectification is to troubleshoot the problem. Although saggy floors are very noticeable, you’ll still have to take measurements from the floor to your ceiling across the whole floor. 

The information that you collect will enable you to identify the areas of sag and decide on the best method to fix the areas. Although the building codes and standards allow for a certain level or degree of sinking, you must repair any noticeable sags. 

If you want to check the extent of sag even better, you can employ a carpenter’s level that is put on a four-foot 2-by-2-inch board. 

Alternatively, you can apply a small rolling bottle or ball on the floor and check for the speed and direction of the rolling. If the sags are massive, the ball or bottle will move faster. 

2. Underfloor Examination

It would help if you got under your floor to examine it from below using a bright flashlight. Here, you should check if any breakages are appearing on the joists. Most of the time, the joists having a crown side facing down always sag with time. 

To correct the issue, you should get some adjustable and temporary columns to reinforce the joists. 

3. Footings And Post Support

It would be best to hold the joists back and offer them support if you had a concrete footing. If you want the concrete foundation to be firm, dig 2 feet deep and slot in your footing support pillar. 

Your footings’ height, width, and depth will rely on the overlying load and standard building codes. You can also incorporate a support beam having columns remaining in place.

Remember to level your ground before you install support piers and bricks. 

4. Install Sister Joists And Girders

At this point, you should install a sister joist to provide the strength needed and support the old beams. Alternatively, you can incorporate a girder underneath the bean and floor but perpendicular to the sagging beam. 

It would help if you marked the beam’s crown to prevent any future sagging due to the upside-down beam. While installing the joist, its high side must face up.

If you follow the methods highlighted above, you can quickly fix any sagging floor in an old house. Ensure that you contact a professional to help you if you lack enough skills and knowledge to fix a sagging floor. 

However, never use green wood to fix sagging because it can shrink and dry, thus translating into an uneven floor. 

How Do You Raise A Sagging Joist?

Raising a sagging joist is easier than you thought. To achieve this, you must set new joists alongside the old ones. The joists should be the same height as the existing ones.

Unless the sagging is under a weight-bearing wall, nailing two 2x4s will function to span almost three joists. 

You can then set your hydraulic jack and post below the beam. Jack joists up about ⅛ each day until they become level. 

If you jack them up too fast, you might experience cracks in the floors and walls overhead.

How Much Is The Cost To Jack Up A Sagging Floor?

The Average Cost

Jacking up or repairing a jacking floor costs an average of $1,000 to $10,000 in the country. The average labor cost per hour for repairing sagging floors ranges between $75 to $125.

However, the exact amount you’ll incur depends on the cause of the sagging, the size of the floor involved, and the type of flooring, i.e., whether it’s hardwood or concrete.

Depending on what is causing the sag, fixing your floor can be pricey since the floor itself might not be the problem. A sagging floor is just a sign of a structural problem and could point to a sinking foundation that could cause more damage. 

Apart from foundation challenges, wood rot, damaged floor joists or subfloors, termite infestations, and waterproofing can lead to your floor sagging or sloping. 

If you have an old home, there is a high chance that you’ll experience challenges with uneven floors and sagging. The same happens to homes that have been infested with termites or flooded. 

As a homeowner, you should never ignore the problem of a sagging floor. Before you contact a specialist to repair the floor, at least estimate the costs of repairing the floor. 

Cost Of Repairing Sagging Floors Caused By Termite Damage

If you have termites on your floor causing it to sag, then it’ll cost you about $250 to $2,000 to remove them. Termites can eat subfloors or floor joists and destroy the support structure under the floor.

Most pest control companies will charge either per cubic foot or per linear foot for any active infestation. However, for preventive treatments, these companies will charge per square foot.

If you notice any termites in your home, you should contact a fumigation expert immediately before the damage is caused. 

The Cost Of Fixing Floors Installed Improperly

There is no hiding that it might lead to sagging if you don’t fix your floor well. The cost of correcting sagging resulting from improperly fixed floors depends mainly on the material you use. 

For instance, marble floors will cost at least $3,000, while vinyl floor repairs will cost you about $200. 

A sagging floor resulting from improper fixing is one of the cheapest and easiest sagging problems you can fix. All you need is to pay a qualified professional who will do the work for you. 

In most cases, a specialist can charge you about $75 per hour. 

Damaged Subfloors

Fixing a damaged subfloor will cost you about $35 per square foot. You’ll also have to pay a professional to pull the flooring up. After subfloor repairs are made, the floor should be put back down to its position. 

A damaged floor could result from termites infestation or water-related damages. If you want to check the exact cause of the damage, a professional should remove the flooring and inspect it accordingly.

In most cases, professionals charge a flat rate. 

Deteriorating Posts And Floor Joists

The installation of new joists will cost between $100 to $300. Damages to joists are among the most common causes of sagging floors since they offer support. Deteriorating beams, posts, and floor joists result from dry rot, water damage, or termite infestation. 

If you want to check and diagnose the joists problems, you should involve a professional who will pull up the subfloor and flooring to inspect their condition. Inspecting joists becomes easier if you have a basement.

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Water Damage

Depending on the scale of the damage and what you need to repair, the cost of repairing a sagging floor due to water damage ranges between $2,000 to $6,000.

Water from flooding, waterproofing problems, and leaks can cause rot to floors, subfloors, and damage joints. The result is a sagging of the floors.

Repairs here involve getting rid of any mold, drying wet areas before making repairs. If you want to prevent future problems, consider dehumidifying.


Fixing a damaged concrete foundation will cost you about $2,400 to $6,800. In cases where a hydraulic lift is required to lift the house, you might spend up to $10,000. 

Depending on the level of structural damage and size of space, a crawl space repair costs about $6,000.

If your house sits on dirt, it can compact and lead to your foundation sinking. Foundation-related repairs constitute the most expensive repairs for sagging floors. 

Hiring a professional foundation specialist or structural engineer to level your house or jack up the floor is the best option for you. 

Is A Sagging Floor Dangerous?

Sagging is dangerous and can even cause injuries and further damage if you don’t address it.

There is no denying that a sagging floor is very annoying. However, you might be discouraged from doing repairs on your floor due to the high cost involved. Some people think that fixing a sagging floor isn’t a must.  

You should repair the sagging joist immediately to avoid the following dangers:

Cosmetic Issues

It might not be top on your list, but it’s a critical thing to consider. A sagging floor presents a huge cosmetic challenge. 

The sagging is not only a problem for the floor but also the internal decorations in your home. For instance, if the sagging becomes severe, you find it challenging to put up tables, bookcases, chairs, and other decors. 

If you notice that your chairs find it hard to balance and sit in position, contact a professional. 

Tripping Hazard

In most cases, a sagging floor can lead to tripping hazards. Your brain is programmed to walk on stable ground. If the ground is sagging in any way, you might end up tripping. 

The problem is even more defined in children, disabled individuals, and the elderly. If you notice even a slight sagging, you should repair it or call a professional. 

Complete Collapse

The worst-case scenario is your floor collapsing completely. This will happen if your floor has been sagging for quite a long time and you have ignored the problem. 

The more you ignore the problem, the more it increases undue pressure on your sagging floor, leading to more sagging. Eventually, the floor can break entirely.

To avoid your floor collapsing completely, you must contact a professional immediately if you notice any sagging.

What Are The Common Causes Of Sagging Floor Joists?

There are several causes of sagging floor joists, as we’ll highlight below:

Faulty Floor Support Structure

A poor design of the structural support of the floor is the most common cause of sagging in floors. When the floor joists begin to bend downwards because of the weight and pressure of the underlying material, the floor will sag without question. 

If you want to fix or repair sagging floor joists effectively, you should install new support structures, including jacks. It would help if you located every jack appropriately, minding its bearing weight and the joist’s strategic location. 

Moisture Problems

It would help if you inspected whether your floor is sagging due to moisture-related challenges or not. If it’s sagging due to moisture, you must dry out the crawl space. You can also seal any leaks from outside elements. 

Settlement Weight

If the floor is sagging because of settlement weight, it would be best to install several jacks to support its massive weight. Depending on the occurrence level, you can even reinforce the foundation with push piers to keep it safe and stable. 

Signs Of Sagging Floor Joists

Although you might think that spotting a sagging floor joist is obvious, there are several things that you should watch out for. Some of these things include: 

Crumbling Or Cracks On The Walls In Your Home

Sagging floor joists can lead to issues on your walls. You should check out for fissures or cracks in the joints and corners. 

Door And Window Problems

The doors and windows on your house should fit perfectly. However, the situation changes when you have a sagging floor. They will either be too tight to open or too loose. 

Lack Of Support

In an older house, you might notice larger spans between the long floor joists and beams. There will also not be enough support on the floor. 

Sloping Floors

Many homes have uneven floors. The uneven floors may result from moisture, settlement, or long spans. If your floor isn’t even, there is a high chance that the floor joists aren’t offering enough support as they should. 

Bouncy Floors

If you hear a rattle every time you pass by a corner, then your floor is operating under minimal support. A bouncy floor will cause furniture to vibrate and shake as a result of getting inadequate support.

If you note that your floor isn’t feeling firm, it’s a sign that it needs additional support. 


Fixing a sagging is easy if you understand the procedure. It’s also critical, especially if you want to stay in a stable and peaceful environment. If you ignore sagging floor joists, you might encounter different challenges that will not only make your life uncomfortable but put your life at risk. 

If you want to notice any signs of a sagging roof, you should do regular inspections. However, ensure that you wear protective clothing during the exercise. 

It would help if you involved a professional foundation specialist or structural engineer in helping you fix your sagging floor joist. We hope you manage to stay in a good environment that has a stable floor.


Hubert Miles | Licensed Home Inspector, CMI, CPI

Hubert Miles is a licensed home inspector (RBI# 2556) with more than two decades of experience in inspection and construction. Since 2008, he has been serving South Carolina through his company, Patriot Home Inspections LLC. As a Certified Master Inspector, Hubert is dedicated to providing his expertise in home inspections, repairs, maintenance, and DIY projects.