Rim Joist

What Is A Rim Joist?

Joists are the main structural elements that make up a home's floor and ceiling frame. Typically, floor and ceiling joists are framed out of different sized 2x or engineered lumber.

Once framing is complete, floor joists are covered with a plywood subfloor and finished flooring like tile, wood or carpet. Most joists are spaced a minimum of 16 inches on center apart.

The wood that butts up to floor joists and wraps around the perimeter of the floor framing is called a rim joist. They are also referred to as a band joist.

If you look at a house from the outside as it's being framed, you'll notice a band of solid lumber running along the side of the floor frame. This is the rim joist.

The function of a rim joist is to give strength and stability to the other floor joists. The ends of the floor joists typically but up and nail into a rim joist which prevents them from tipping over to the side.

Rim joists help keep floor joists level and upright. Nails are driven through the rim joist and into the end of the floor joist which keeps the entire floor system tied together.

On a typical house, the rim joists sits on top of the foundation wall sill plate. After the plywood subfloor is installed, a wall can be built on top of the rim joist.

In cases like these a rim joist is considered load bearing. In other situations, for example the edge of a deck, a rim joist may not be load bearing because nothing is built on top of it. However, most decks use the rim joist to help secure railings and stairs.

Band Joist Vs Rim Joist

Once framing is complete, floor joists are covered with a plywood subfloor and finished flooring like tile, wood or carpet. Most joists are spaced a minimum of 16 inches on center apart. The wood that butts up to floor joists is called a rim joist. They are also referred to as a band joist.

The terms band joists and rim joists are interchangeable and are both used for the same structural members.

When taking into consideration the joists on the longitudinal sides of the perimeter of the floor frame, the term rim joist is used.

On the other hand, when referring to longitudinal side joists along with the shorter end joists collectively, the term band joists is used.

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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.