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Floor Joist

Floor joists are an essential part of the subfloor framing. They need to always be in good condition to support your home’s weight.

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Not every home is built directly on a concrete slab. Some have a basement or a crawl space, which require a floor joist system. It’s this underlying structure that provides support for your furniture, flooring, and everything else inside the house. Let’s examine the term floor joist and look at the different types of joists and some of the problems that can damage them. 

Floor Joist

What Is a Floor Joist? 

A floor joist is a horizontal structure that’s used in framing open spaces. When combined with the floor framing, joists help to stiffen the subfloor shearing, enabling it to function as a horizontal diaphragm. The beams are usually installed after the crawl space or basement has been built. Once in place, they support the floor above. Joists must be parallel, equidistant, and span between beams or load-bearing walls, which transmit their weight to vertical members. 

Joists are usually installed during home construction. A professional can help you choose the right type and install it properly on the subfloor. Floor joists span support beams or walls and are set up at regular intervals. 

Types of Floor Joists 

There are three major types of joists used in house construction. Each type has its pros and cons, which is why carpenters tend to have a favorite option. 

I-joists: One of the eco-friendly joists, the I-joist resembles the letter “I”. Its ends are made of solid wood while the middle section consists of OSB or plywood. These joists can extend more than 20 feet. I-joists have minimal flex and higher load capacity than lumber joists, which makes them good for ceramic tiles. Some designs come with holes that utility lines are run through. 

Solid lumber: In the past, they were the only joist material. Solid lumber is a low-cost option, though price ultimately depends on board size, wood grade, and the wood species. All these three factors also affect the joist’s span. This joist holds up well against fires and floors. When using them in construction, it’s advisable to adhere to local codes and factor holes for utilities. 

Open web floor trusses: They are made from 2 x 4 boards and have a web of diagonal boards that are fastened with plates. Since they have open spaces in the middle, trusses make it easy for builders to run utilities right through them. They flex more than I-joists but less than lumber joists. Their unique design means they can stretch more than the other joists. 

Signs of Failing Floor Joists 

Unfortunately, floor joists can rot and decay and this can lead to serious structural problems, including: 

  • Slopping, sagging, or uneven floors 
  • Skewed or uneven window and door frames 
  • Tilting or sinking crawl space supports 
  • Moist, rotting wood 
  • Cracks in the drywall 
  • Bouncy or creaking floors 

It’s not advisable to perform a DIY joist installation or fix damaged lumber joists. Due to their technical nature, some types of joists require a carpenter or contractor. If your joists develop problems, ask a home inspector or structural engineer to come and evaluate them before making recommendations for repairs. 

Causes of Floor Joist Issues 

These three things are the leading causes of floor joist failure. 

Poor support design: When joists are poorly designed and installed, they become incapable of supporting the load above. Any extra weight will weaken the joists or cause them to sag. Some of the common support design issues include the use of few floor joists, over spanned floor joists, or poor joist spacing. 

The weight of your home: Floor joists can only support a certain amount of weight. Any extra load may damage them. If you suddenly add extra weight to any part of your home during a renovation, you may end up with a cracked floor joist, which can seriously impact your home’s overall stability.  

Moisture and humidity: Excess moisture is another leading cause of floor joist failure. Remember, joists are made of wood, which decays in the presence of moisture. 

How to Fix These Issues 

If you want to prolong the lifespan of your floor joists or maintain their stability, you need to begin by combating moisture in all areas of your home, especially the crawl space or basement. 

Next, check and fix all broken or damaged floor joists. A crawl space repair contractor is your best bet as they have the knowledge, experience, and tools to fix joists. 

If your floor joists are severely broken and can no longer provide adequate support for the floor above, it is time to replace them. Consider adding extra floor joists to provide additional support.  

Floor joist replacement is both expensive and invasive. As such, we highly recommend that you handle any floor joist issues as soon as you notice them.  

Joists that hold up the home may need additional points of support. You can buttress them by installing the IntelliJack™ Crawl Space Stabilizing System. What this system does is stop your floor joist from sagging. Plus, it is easy to adjust in case your home shifts further in the future.  

Lastly, seal up the crawl space with a 20-mil plastic vapor barrier. It’s going to lock out moisture and mold spores that threaten the joists, as well as reduce pests’ interest in the space. Other than sealing off moisture, encapsulation promotes healthy air circulation in your home and maintains healthy humidity levels.  

Like every fixture that’s made from lumber, floor joists decay, bend, and fail, resulting in sagging or uneven floors. This can be a safety hazard and a precursor to serious structural issues. Contact JES Foundation Repair to schedule a free crawl space repair inspection today. 

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