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Rim Joists

Rim joists are attached perpendicular to the joists and provide lateral support for the floor above.

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Your subfloor has several joists that help support your walls. One of these is the rim joist, which can let in moisture and air into your house.  

Let’s delve into the world of rim joists, what purpose they serve, how contractors install them, and how to insulate yours. 

What are Floor Joists?  

A rim joist, or a band board, is a component of your subfloor that helps bear the weight of your walls. This joint works in conjunction with two outer joists, forming a band for your floor’s framework.  

In a two-story home, the rim joists bear the weight of the wall, the upper floor, and its wall, and the roof.  We hope you now have an idea of how much of a load a single rim joist can bear.  

The conventional material for creating joists is solid wood that’s free from knots. Engineered wood products and laminate wood are other common materials. Often, the material is of the same size as other joists ensuring that rims are flush with joists on top of them. 

What Do Rim Joists Do?  

A rim joist or band board provides lateral support for the other joists in your subfloor preventing them from collapsing under your structure’s weight. On top of this, it caps off the terminal areas of other joists. This in turn prevents cavities that might expose your home to outside air or moisture. Another thing that the rim joist does is provide a mass of wood for nailing during the installation of your sheathing, siding, or trim boards. 

Telltale Signs of Failing Floor Joists  

A sagging floor is the biggest telltale sign of damaged joists. Other signs to look out for include:  

Once you notice any of these signs, you need to have the joists repaired immediately. 

Common Floor Joist Issues  

Understanding typical floor joist issues is crucial to coming up with the perfect solution. Some common floor joist problems include:  

Wood Rot  

The support holding up your home comprises wooden joists. Without proper sealing and waterproofing, your crawl space becomes prone to moisture and humidity. These conditions create the perfect breeding ground for mold and wood rot. Over time, these fungi can destroy the integral strength of your joists, posts, and girders. Hence, your joists may sag and cause the floor above your crawl space to sink or slope.  

Poor Construction  

Sometimes, contractors build crawl spaces with joists that are too few, while other times, the spacing is the issue. When there aren’t enough joists to support the weight of your household, the beams may begin to weaken and sag down. This may cause uneven floors and create an unsafe environment for your home.  

Termite Damage  

Termites eat just about anything that contains cellulose, including floor joists. When termites attack your floor joist, they compromise its integrity, leading to loose or saggy floors.  

Fixing and Protecting Your Joists  

Any damage to your floor joists presents a safety problem and needs immediate repair. To protect your frames from rotting, start by addressing the moisture issues in all areas of your home especially the basement or crawl space. Ask your carpenter to check and fix broken or damaged floor joists. Where repairing is not sufficient, consider replacing the joists altogether.  If the floors above still feel wobbly after your joists are repaired, consider adding extra floor joists to provide additional support.  

We also encourage you to have the crawl space, which houses the joists, sealed. What this will do is it will lock out moisture and make it difficult for pests to get in that may threaten the integrity of your joists. This is something Groundworks can help you with. To get started, schedule a free inspection

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