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Rotted Floor Joists

Rotted floor joists are not just a problem sign of serious issues within your property—they can also be direct contributors to further damage. Acting quickly is crucial.

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Straight, strong walls, a solid roof, and firm, stable flooring are just some of the things that homeowners in and around Nashville, Tennessee, take for granted in their properties. Sadly, these things are not always guaranteed. When you have rotted floor joists in your home, damage to your property’s flooring is certain. Unfortunately, this is not where the issue ends. 

Rotted floor joists are, in and of themselves, a problem sign for damage and problems that already exist in the property. Wood rot fungus only flourishes in the right conditions; dampness is a necessary component. This dampness, however, is the underlying issue that rotted floor joists stem from and must be corrected to prevent reoccurrence.

What Is Wood Rot? 

To put it simply, wood rot is a natural process that is caused by the presence of certain fungal spores and growth. It causes certain parts of wood to break down, thereby robbing the wood of its structural integrity. In nature, this allows the wood to break down and enrich the ecosystem. In a Birmingham, Alabama, home, it is a serious and dangerous process that is to be avoided at all costs.

rotted crawl space

The Types of Wood Rot 

Wood rot can take three main forms. While they all have slightly different telltale signs and processes, they all do the same thing; cause dead wood to decay. In nature, this serves an especially useful purpose. In a home, however, it spells trouble. After all, all wood in a property is dead wood. 

Brown Rot 

Also known as dry rot, brown rot is one of the most worrying forms of rot to find in your home because of the speed at which it moves. The fungal spores that cause brown rot attack the cellulose and hemicelluloses in the wood that they spread through, causing rapid strength loss and breakdown.  

Wood that has brown rot will start to crack and flake. It may even look slightly burnt in different textures and will change in color. The wood will crack against its grain and will start to split as it becomes dry, brittle, and powdery. 

White Rot  

White rot is one of the most immediately recognizable forms of wood rot, and it’s one of the two forms of wet rot. The spores that cause white rot to attack the cellulose, hemicelluloses, and lignin in the wood, usually take on white, gray, or yellowish spots in the areas that are rotting. This form of rot is less likely to cause splitting and fragmentation. 

Wood that is facing white-rot will start to take on a spongy or soft texture and will lose strength over time. Rather than being brittle and splitting, however, wood-facing white rot is more likely to become springy and start to bend. Over time, it will become too weak to withstand any real pressure and finally snap. 

Soft Rot 

The second form of wood rot is called soft rot, and it is the form of rot that progresses most slowly. Caused by fungi that attack the cellulose, hemicelluloses, and lignin in the wood, it leads to significant structural decay and loss of strength in wood. This is also the rarest form of wood rot, however, and is harder to diagnose than others for non-professionals. 

Wood dealing with soft rot may take on a honeycombed appearance that leads to it being misdiagnosed as a termite or bug infestation. Alternatively, soft rot can cause discoloration and crack like brown rot. Wood facing soft rot will become soft, spongy, and unreliable. 

The type of rot you have in your home is not hugely important to anyone other than the professionals treating it. The only exception is brown or dry rot because this kind is notorious for spreading throughout whole structures with alarming speed.

What Rotted Floor Joists Can Signify 

Rotting flooring or joists around your property are signs of dampness and fungal spread. However, there are a few potential sources when it comes to dampness and humidity. These are just the most likely. A professional will be able to figure out which of these issues is to blame for your rotted floor joists during an inspection.

mold and rot in a Montgomery crawl space

Structural Damage 

One of the most worrying possibilities is that the dampness which has led to rotted joists in your property’s crawl space is being caused by structural damage. Any damage to your foundation and foundation walls, for example, will allow groundwater to seep into your crawl space. This will create a damp and humid environment that can lead to rot and other forms of fungal and bacterial growth. 

Internal Leaks 

Assuming the structure of your property is sound, the most probable cause of dampness, humidity, and wood rot in your crawl space is a low-level, internal leak in your home. A small crack in your pipes, for example, or an appliance with a weak inlet or outlet can cause sufficient dampness and humidity to allow wood rot to take root and spread. There is also the chance that a plumbing flood is the root cause of the underlying dampness, even if you acted quickly to stem the flow of water and drain your crawl space. 

High Humidity 

Another way that dampness could find its way in your home is by localized damage or exposure. 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. You will recognize humidity by signs like condensation

Each of these issues can cause a host of secondary and tertiary issues to develop over time. As such, learning to recognize the warning signs of these issues can be an incredibly useful skill for any homeowner. 

Problem Signs You Should Be Aware Of 

These problem signs can help you to spot issues in your crawl space before your floor joists begin to rot in the first place. This could save you a lot of time, money, and stress, so be sure to act quickly if you feel there is something wrong. 

buckling foundation walls in Hoover

Leaning or Bowing Walls 

Damage to your property’s crawl space joists and supports or foundation can cause widespread instability in the structure as a whole. Leaning or bowing walls are just one result of this. If you notice your walls seem to be uneven or buckling, you should contact a professional immediately. There are several potential causes of this kind of damage and none of them are good.  

Bad Odors 

A persistent and unpleasant or musty odor in your property that simply will not shift no matter what you do is a severe problem sign of dampness and rot. It can also be a sign of pest infestation and a few other issues you should not underestimate. Call a professional to assess the situation as soon as you notice odors like this to prevent structural and health issues. 

Mold and Mildew 

Mold and mildew go hand in hand with dampness and humidity in a property. Like wood rot, these are fungal growths. Unlike wood rot, mold and mildew can be actively harmful to your health and well-being, as well as the health of your family. Not all species of mold are toxic, but some can be lethal to those who have underlying conditions that impact their immune and respiratory systems. Black mold is especially toxic and can cause fainting, dizziness, and even seizures. 

Floor and Wall Gaps 

Gaps between your walls and floors are a fundamental problem sign that should not be overlooked. These gaps show that something is exerting enough pressure to cause them to separate. Furthermore, once these gaps form, your property’s floor will become more unstable and start to sag more dramatically. In fact, it could even lead to collapse over time. 

Pooling Water 

Pooling water in your property’s crawl space is a significant issue and your main priority should be finding out where the water is coming from. The source of the water is the real problem, though the dampness that it causes can easily lead to other problems forming in a brief period of time. 

Bouncy Flooring 

Your floors should be always firm and stable underfoot. If you notice a springiness or bounce underfoot, this is a strong sign of damage that you should not ignore. Rotted floor joists are not the only underlying cause that could be at work. For example, the joists in your crawl space could be over-spanned as a result of cracking, flawed materials, or even poor design. 

If you see any of these problem signs around your home, you should act quickly and seek professional guidance. Whatever you do, do not try to tackle this kind of floor damage alone. Getting the right help without delay is vital to ensuring that you prevent avoidable damage.

Rotted Floor Joists


A sagging, uneven, or springy floor can be the result of many different issues in a home. In fact, this kind of issue is often the result of a mix of underlying issues that all must be addressed to get a solid solution. 

Structural Damage 

The whole structure of your property is reliant on every part of itself to ensure optimum support and stability. While some parts of a home are particularly important, like the foundation, for example, any serious structural damage in your home can feasibly lead to issues like sagging or uneven flooring. In fact, if the issues are left to grow unchecked, they could lead to the collapse of affected walls and floors. With that said, the issues most likely to cause sagging floors are issues in your property’s foundation. 

Settlement, subsidence, and lateral movement can all cause sufficient damage to the supports and joists inside your crawl space and lead to a sagging or uneven floor. Each of these issues is most likely to be caused by problematic foundation soils. Expansive soils, for example, are very unstable and swell or shrink depending on their saturation. This can cause sinking or settlement. Weak or loose soils, by contrast, can be washed or blown away and cause settlement as a result of voids being formed under or around your home. Either way, foundation damage is a common cause of sagging flooring. 

Rotted Floor Joists 

A more localized cause of sagging flooring is some kind of damage to the joists that support your property’s flooring. Joists that cannot support the weight they were intended to are known as over spanned joists, and they can come about as a result of damage, decay, or poor design. Rotted floor joists fall into the category of decay or damage and are hard to deal with. 

Joists that are failing as a result of rot will fail more slowly than those that are failing because of deep cracks or structural movement. This means you will have a little more time to act. You will first notice a slight spring or bounce in your flooring. This will develop into a defined sag and could eventually lead to the collapse of the floor as a whole.

Damaged flooring can be hard to tackle, and for this reason, many homeowners are tempted to simply replace the flooring once the issue progresses to a certain point. However, this is not always the best option (or even a viable option). 

When To Replace 

There are some cases in which replacing a whole floor is the appropriate choice, but this is far less common than you might think. In fact, replacing a sagging floor is almost never the best option, because it is extremely time-consuming, disruptive, and costly. What’s worse, simply replacing the floor will not address the underlying issues that led to the damage in the first place. 

This means that you will have to deal with the cost of replacing the floor, as well as the cost of installing repair solutions to address the underlying causes. The only situation in which it is best to replace the whole floor is when the wood rot has spread throughout the floorboards, as well as the joists and supports. In this case, it would be dangerous to keep the floor at all. 

When To Repair 

As you might imagine, we feel that it is far better to repair your property’s flooring unless it would be actively dangerous not to. Thankfully, it is far easier to repair a sagging floor than to replace it these days, even when the joists are rotted. From crawl space jacks that can be used to add extra support to chemical treatments to kill the rot, there is a plethora of options on the market. 

You should have the advice and guidance of a professional during this process to make sure that you are getting the right solution for your home. In most cases, the repair process will be complex and will require a combination of solutions to ensure that each underlying cause and co-occurring issue are resolved. Finally, you should remember that the best time to repair your property’s flooring is immediately after spotting the warning signs. Structural repairs are best carried out early.

It can be possible to stabilize or fix a rotted floor joist, but it is a specialist and complex process that must be undertaken by a professional to ensure the health of your home and your safety. DIY could end very badly for you and your home. 

The Dangers of DIY 

DIY of any kind is risky, but DIY structural repairs, in particular, are incredibly problematic. This is why we recommend that you do not attempt to repair a damaged floor or rotted floor joists without professional help. There are simply too many things that could go wrong. Primarily, there is a very real chance that you will cause more damage to your home by trying to repair the issues alone, especially if you try to sister the rotted joists. 

While sistering is a commonly recommended repair and bolstering method on DIY blogs and sites, it is notorious for causing more damage to the joists in question. This is because sistering requires you to move a damaged joist out of the way to add more materials to it. This movement can weaken the joist and lead to a more exacerbated sag in the flooring. In fact, it could even lead to the flooring collapsing over time, if you are not careful. Even if you try to undertake more professional repairs there is a high chance that you will cause damage to your home or even injury to yourself. 

The Professional Process 

When it comes to rotted joists and damaged flooring, the professional process of repair can differ from home to home for several reasons. This is, first, because of the number of underlying issues and connected forms of damage that can be involved in allowing wood rot to flourish. The process only gets more complex when the dampness that allows wood rot to flourish is caused by issues like foundation damage. These kinds of repairs can be actively dangerous because of the equipment needed to undertake the work that is required. 

The actual process of removing, replacing, or repairing rotted floor joists and supports, however, is a little simpler. First, the rot must be treated and removed to prevent it from spreading further and causing damage to the rest of your property’s structure. This means treating the rotting wood with chemicals and dehumidifying the crawl space. After this point, the floor must be properly supported. Installing crawl space jacks is the most common way to do this. Once the rot has been treated and the floor has support, many homeowners choose to waterproof their crawl space to prevent the recurrence of wood rot and damage in their homes. This process has many stages, but it is relatively straightforward. 

Expert Crawl Space Repair From AFS Foundation & Waterproofing Specialists 

If you have noticed signs of damage to your property’s flooring, or there are warning signs of dampness, humidity, and rot in your home, you should act quickly. We at AFS Foundation & Waterproofing services are here to help. We have decades of collective experience when it comes to dealing with these kinds of issues. As such, you can expect great results from our contractors in Birmingham, Huntsville, and Mobile, Alabama, and Nashville, Chattanooga, and Knoxville, Tennessee. 

Whatever the issues in your home look like, we will always begin with a thorough inspection. You can book your free inspection appointment online or by calling our team directly. We will send a professional to your home to discuss your needs and the needs of your home. After which, they will undertake a full inspection and provide you with a written estimate for repair solutions. These appointments come with no obligation to book repairs, however, so please do not rush into making a decision.


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