Skip to Main Content
Crew member working in crawl space

Over Spanned Floor Joists

The joists that support your main floor are hugely important to your home; if you have over spanned joists in your home, your floors will suffer hugely.

Schedule Free Inspection

There are some things that we might take for granted as homeowners: strong walls, a solid roof, and stable floors are just some of them. Unfortunately, not all these things are guaranteed. Over spanned joists, for example, are quite common in Cincinnati and Columbus, OH. What’s worse, many homeowners overlook them for a long time because of the subtle problem signs that are associated with them. 

Over spanned joists can be caused by a number of issues within your home, but they can also cause huge amounts of secondary damage if left to spread unchecked. Over spanned joists are actually a sign of advanced structural defects or decay within a property. As such, it is important that you learn how to spot them and act quickly when you see them. So, what are over spanned joists? What causes them? And what should you do when you think you have this issue in your home? 

What is Over Spanning? 

To put it simply, joist span is the space between joists and the load that they are capable of safely carrying. A healthy joist span will ensure that your floors and ceilings are even, firm, and robust. When you have over spanned joists, however, they are no longer capable of carrying the weight they need to. As a result, the surfaces that they are meant to support will suffer. 

This is more common than you would think. For example, while it might seem obvious that using bigger, thicker beams will increase the span of the joists, this is not always true. If the wooden supports are too heavy, they will add strain and they could even cause over span. 

Signs of Joist Damage 

Floor and ceiling joists are incredibly important to the stability of your property’s structure and interior. When they become damaged, the floors and ceilings that they are supposed to support will quickly deteriorate. Being able to spot the warning signs of damage is incredibly important if you want to limit the damage that your home experiences. 

The most common signs of joist damage are: 

Mold and Mildew 

Mold and mildew are general signs of dampness, humidity, and damage to property. Recognizable by the appearance of blotchy, raised, fuzzy patches of discoloration on walls, floors, or even textiles, mold can also produce a strong, musty smell. Certain species of mold can also eat away at organic materials like wood, cardboard, and fabric, while others can be actively harmful to your health and well-being. 

Wooden floor joists that are affected by mold are also likely to be dealing with rot as a result of dampness and humidity. This can change the appearance of the wood, leading to it crumbling and flaking. 

Bulging or Sagging 

Joists that are struggling to deal with the weight of the surface they are supposed to support will quickly start to bend and sag. When the pressure becomes intolerable, the support joists may start to crack as well. This will start as low-level unevenness but will quickly progress into a visible bulge or sag. 

Water Damage 

Water damage can be invisible, in many cases, but there will usually be some kind of sign upon investigation. The most common sign of water damage, which can be seen across almost every material, is staining. Concrete, wallpaper, wood, drywall, and textiles will all stain when subject to serious water damage. 

Other common signs of water damage include warping, peeling, flaking, and crumbling. If you see these signs on a support joist, it is important that you have it assessed quickly. 

Bouncy Flooring 

Your floorboards should be firm and strong underfoot. If you notice that they feel springy or bouncy, this is a strong sign that something is not quite right with the joists that support the flooring. Either they are damaged, or they are over spanned and have left sections of the floor to go without proper support. 

Floor and Wall Gaps 

Unevenness or gaps between your flooring and the walls that attach to it is a serious sign of ongoing damage to your home. In fact, this is often a sign of foundation damage in a property. Issues like subsidence and settlement are most commonly at work when the gap between the floor and walls is vertical. 

If, however, the floors are pulling away from the wall horizontally, it is far more likely that the flooring itself is sagging and causing the gaps. 

These can also be warning signs for deeper issues of course. Indeed, over spanned joists are often a symptom of other kinds of damage and instability in a home. 

What Causes Over Spanned Joists? 

There are many different things that can cause damage to your property’s supports and joists. Many of these things are issues in their own right, however, which is why it is important to contact a professional as soon as you notice the warning signs in your home. 

Foundation Damage 

One of the most common and serious underlying causes of over spanned joists is foundation damage. This makes sense because a shifting foundation will also cause your floor’s supports and joists to shift, thereby leaving the floorboards themselves with sporadic support. The most common kinds of foundation damage that impact homes around Cincinnati and Columbus, OH, are settlement and subsidence. 

Settlement is a process that sees large chunks of a foundation break away and sink into the earth below. Generally caused by the shrinking of expansive soils during periods of drought, this is a serious problem that will impact your whole home, not just the floor joists. 

Subsidence, by contrast, is an issue that sees a property’s foundation sinking into soft, loose, or excessively wet soil that has lost its ability to support the structure. This will cause the whole structure to shift and distribute the weight unevenly. As a result, cracks will start to form. This can lead to spreading cracks, bowing walls, and a number of other issues. So, while foundation damage can cause over spanned joists, they might be the least of your worries. 

Dampness and Humidity 

Dampness and humidity themselves can be caused by a number of issues, but they are also a leading cause or contributing factor to over spanned joists in many cases. This is because of the ways in which wood reacts to persistent saturation over time. Wooden support joists that are consistently damp will often start to rot and form mold. This will lead to the weakening of the joist itself and eventually show itself as sagging, bulging, or even the collapse of the surface that the joist is supposed to support. 

Pest Infestation 

There are not too many pests that can cause huge amounts of damage to a wooden support joist, but there are others that can. Pests like termites can be very hard to spot, but they will wreak havoc in any home that they take root in. Dry-wood termites are not native to Ohio, of course, but they can be brought into a home in old furniture and décor. As such, you should carefully inspect any new items that you bring into your home to ensure that they will not be letting pests into your property. 

Construction Defects 

Over spanned joists can be caused by construction and material defects, as well as damage to the wood and your property as a whole. Floor joists are made to span certain distances and bear certain weights. If the space between joists is miscalculated, or the wood used has defects in it, the joists will suffer very quickly. Over time, this will cause your floor to sag, warp, and even collapse if it is left unattended. 

Each of these issues can lead to your floor joists becoming over spanned with frightening speed. There are a number of reasons why this should worry you, but the most obvious issue is the lack of support provided. 

Over Spanned Joists


Technically, there are joists and support beams located throughout your home, but the main support joists in any property are found at the lowest point of a house. This will either be the crawl space or basement. The joists and their placement will change, of course, depending on whether you have a crawl space or a basement. 

Under the Main Floor 

If you have a crawl space rather than a basement, you will find your main support joists running from the foundation walls across the span of the crawl space. Because of this, they actually form an integral part of the support system that holds up your whole house. As you can imagine then, damage to joists in a crawl space can be particularly worrying for the health of the home as a whole. 

This placement makes floor joists in an unencapsulated or non-waterproofed crawl space particularly vulnerable to damage. Of course, this is because exposed crawl spaces are far more prone to damage as a general rule. Water is far more likely to seep up into the crawl space from the earth, for a start, and crawl spaces that have uncovered vents will be more prone to condensation and even flooding during seriously bad weather. 

Connected to Basement Walls 

Support joists that are found in properties with basements are more likely to become over spanned or damaged as a result of structural shifts and changes. This is because they are less exposed to the elements than joists in a crawl space. Some basements may be prone to dampness, after all, but it is unlikely that support joists in a basement will come into contact with water directly when there is flooding in a basement. 

Some basements also have limited joist placements that are designed to give additional support, rather than holding all the weight themselves. However, that doesn’t mean that there will be no problems if they become over spanned. In fact, if these joists become over spanned because of foundation problems or bowing walls, for example, they will exacerbate the instability that the floor above is facing and lead to more serious repercussions. 

If you have over spanned joists in your basement, repairing them will be a relatively complicated and intensive process that will require the resolution of underlying problems before any work can be done on the joists. If you have a crawl space that is experiencing over spanned joists, however, the solution could be a little closer to hand. 

Why You Shouldn’t Sister Joists 

If you have damaged joists or supports in your crawl space, it can be very tempting to attempt to sister the damaged wood. This is a very old method of reinforcing support beams and joists that has now been proven to be largely ineffective. As well as being more of a way to buy time (the sister material will inevitably start to fail, too), the process of sistering can actually cause more damage to a beam or joist. So, this isn’t really a good repair method. 

Sistered joists and beams are very likely to collapse over time, and could even lead to damage to otherwise healthy joists as they are forced to put up with extra strain over a prolonged period of time. This will make the overall cost of repairing your property higher, and the process more complicated. So, sistering damaged joists is not really worthwhile for most people. 

Crawl Space Jacks 

There are some situations in which replacing a damaged or over spanned joist is the best, or only, solution, but these are rare. After all, replacing such an important support in your home is a time-consuming and labor-intensive process that can go wrong if the process is miscalculated in some way. So, like concrete floor replacement, it is possible, but far from the most efficient and cost-effective option in most cases. 

Crawl space jacks, however, are a versatile and cost-effective tool that can be used to provide support to your property and relieve the stress on over spanned joists. The installation process for crawl space jacks is quick and relatively non-disruptive. In fact, it is almost entirely non-invasive. Once crawl space jacks have been installed, they do not need to be addressed again at any point unless a wider issue causes them to shift. This means that they are also a permanent solution. 

While it is very possible to address and repair damaged floor joists, we do not recommend that you attempt this process alone. There are a number of reasons as to why you should call a professional in to deal with your over spanned joists. 

DIY Work Could Backfire 

If you try to tackle your over spanned joists alone, you could run into many issues that are dangerous both to the stability of your home and your personal health and well-being. Your floor support joists are responsible for holding up an immense amount of weight, after all. If you try to implement repairs without professional input or help, you could end up causing the floor to collapse (which would be incredibly dangerous for you and anyone else in your home). 

Before you even get to the point of repair, however, you need to identify all the underlying causes of over spanning. This is not as easy as it sounds. There can be a number of different factors at work, often at the same time, which makes diagnosing the issue in full a little complex if you have no experience or training. Improper diagnosis can lead to an incomplete or inappropriate solution. 

Professionals Know What They Need to Do 

When you hire a professional to assess and repair your over spanned joists and crawl space damage, you gain a number of benefits. First, a professional will be able to properly diagnose the causes of damage in your home and formulate a solution that actually addresses the issues in your home. This means that you can expect the repairs they perform to be effective, efficient, and, most importantly, permanent. 

Furthermore, professionals have access to the best possible products and tools (as well as the skills to use them properly). As such, there is little to no risk of additional damage to your property occurring during the repair process. When you hire a professional to undertake these kinds of repairs, you get a quicker, more efficient repair process, higher-quality results, and the peace of mind that comes with knowing the issue has definitely been resolved. Finally, because of the permanent nature of these repairs, your overall repair costs will actually be lower when you hire a professional. 

Why You Should Worry About Over Spanned Joists 

For the average homeowner, slight unevenness or sagging in a floor can seem like the least worrisome thing going on in a property. However, there are a few reasons as to why you should deal with over spanned joists as soon as possible. If you ignore signs of joist over span and damage to your home, you could end up facing much worse damage like: 

  • Cracking 
  • Increased airflow and mold spread 
  • Floor collapse 
  • Temperature fluctuations 
  • Damage to vital systems 

You see, the most exposed joists in any home tend to be in the crawl space. This is also an area that the majority of your home’s vital systems pass through. From your property’s plumbing system to the electrical wires that run through your whole house, your crawl space acts as a hub for so many things. When your joists become damaged and start to sag, these systems will be put at risk. Likewise, the same forces that are capable of damaging a support joist can also have an impact on your pipes and electrical wires. 

So, as you can see, if you have over spanned joists in your home, the effects on your property and your health can be quite worrying, depending on any other factors that might be at work. Thankfully, there are many things that you can do to repair this damage and restore your home to ideal condition. Usually, over spanned joists simply need some extra support to ensure they can safely bear the weight of the floor above them. Of course, you should not try to take on this work alone. Professional help is the best option at your disposal. 

Call in the Pros to Repair Your Over Spanned Joists 

When your floors start to sag and you worry that you are dealing with over spanned joists, your first call should be to Ohio Basement Authority. We have been the leading crawl space and foundation repair experts in Cincinnati and Columbus, OH, since we opened for business in 2009. Since then, we have helped thousands of homeowners to restore their crawl space, foundation, and property structure to full health. No matter what issues you have at work, we know our team can handle them. 

All you need to do is contact us to schedule a free inspection and repair quote. When one of our inspectors comes to your home, they will assess the obvious damage but also look for secondary issues that may have formed. After doing so, they will provide you with their suggestions and a written estimate for costs. This appointment comes with no obligation, and you will not be pressured to book repairs with us. Take your time to make an informed decision that is good for you. 

Our crawl space experts can help you

Request free inspection
Request free inspection
Our crawl space experts can help you

Publish Date:

Last Modified Date:

Ohio Basement Authority Service Map

Serving Greater Columbus, Cincinnati, Dayton, and Northern Kentucky

Cincinnati Office

1270 Hillsmith Dr.
Cincinnati, OH 45215

Columbus Office

2421 McGaw Rd.
Obetz, OH 43207

Dayton Office

70 Birch Alley, Suite 240
Beavercreek, OH, 45440