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Floor Joist

Floor joists are meant to support your home’s weight, which is why it is important to protect them from moisture and fix them as quickly as possible.

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If your home wasn’t built on a concrete slab, your house has a floor joist system. This system provides support for everything in your home, so it must be properly built and kept in the best possible condition. Let’s take a closer look at floor joists, what their purpose is, types of floor joists, and potential problems that could harm them. 

Floor joists

What Is a Floor Joist? 

If you have ever witnessed the building of a house, you have probably noticed that wooden frame that goes on top of the foundation. A floor joist is a flat structure that, when combined with the floor framing, stiffens the subfloor shearing. These beams are installed after the crawl space or the basement–depending on the type of foundation–has been completed. When everything is in place, floor joists support the floor above. These beams need to be parallel and equidistant. 

Installing floor joists is not a DIY project. A skilled professional should choose the right type of joists and install them on the subfloor. 

Types of Floor Joists 

There are three types of joists contractors use when building a house. Each type has its upsides and downsides, so let’s take a look at them. 


This is an eco-friendly option since I-joists are not made entirely of solid wood. Instead, the ends are made from solid wood while the middle is made of OSB or plywood. These floor joists look like the letter “I”, which is why they are named this way. They can extend more than 20 feet and have a higher weight load capacity. This is why they are great for tile flooring. Some variations come with predrilled holes in them, which are used for holding utility lines. 

Solid Lumber 

Before construction materials were so advanced, solid lumber joists were the only possible option. Although their price depends on several factors including size, wood grade, and wood type, this option is a more affordable one. This type of joist holds up well against fires, and when it is used in construction, it is important to follow local codes and keep holes for utilities in mind. 

Open Web Floor Trusses 

These joists are made from 2 x 4 boards and look like a web of diagonal boards. These boards are connected with plates that keep them in place. Since there is room between diagonal boards, open web floor trusses make it easy for builders to run utilities right through them. Another advantage of floor trusses is they are much easier and quicker to install than I-joists or solid lumber. Therefore, they often present a more economical choice. Also, they stretch more than other joists due to their unique design. 

Signs of Failing Floor Joists 

The problem with floor joists is that they are made of wood and like any wooden structure, they can rot and decay. If you notice that your floors are uneven, or that your window or door frames are skewed, it is time to call professional foundation repair contractors to fix the problem. You should also pay attention to sinking crawl space supports, rotting and moist wood, cracks in your drywall, and creaking floors. 

Do not try to fix this kind of damage on your own. Some types of joists require a professional contractor or carpenter. If you notice any of these signs, call an expert to assess the problem and make recommendations for repairs. 

Causes of Floor Joist Issues 

Several factors can cause problems with floor joists. 

  • Poor support design: Joists must be properly designed and installed because otherwise, they won’t be able to support the load above. Extra weight will weaken them and cause them to sag. If the contractor hasn’t used enough floor joists, or they haven’t calculated the spacing correctly, they won’t serve their purpose. 
  • The weight of your home: When they are building a home, contractors make calculations based on the original size of the house. If you have bought a house and you decide to add another story, keep in mind that you might end up with a cracked floor joist. 
  • Moisture and humidity: As you already know, waterproofing your home is necessary because moisture and water damage can lead to all sorts of problems, floor joist failure included. 

How to Fix These Issues 

Keeping your floor joists in tip-top shape begins with combating moisture in all areas of your home. Floor joists are made of wood, so they can easily rot in the presence of moisture. Therefore, make sure you waterproof your basement or crawl space. If you have noticed that some of your joists are broken, fix them as soon as possible. Contact a contractor in North Carolina who possesses the knowledge, experience, and tools to fix joists. If your floor joists are damaged beyond repair, it is time to completely replace them. This investment costs a pretty penny, which is why it is always better to fix the problem as soon as you notice it. 

In case your floor joists are not able to support your home on their own, don’t panic. With solutions such as the IntelliJack™ Crawl Space Stabilizing System, you can stop your floors from sagging. In case your home shifts again in the future, it is easy to adjust the system. 

In case you have crawl space and not a basement, consider encapsulating it. A vapor barrier will keep the moisture out and your crawl space dry, therefore preventing rot. In addition, it will make it more difficult for rodents and pest to get inside your home. Encapsulation promotes healthy air circulation as well. 

Damaged floor joists can become a safety hazard, which is why it is important to react as soon as you notice the first signs of trouble. Call experts at Tar Heel Basement Systems and schedule a free inspection today.

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Winston-Salem, NC 27103


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Fuquay-Varina, NC 27526