What is a rim joist on a deck or basement? (ANSWERED!)

If you are planning to build a new house, you need to have a basic idea about joists. Rim joists are also known as band joists. If you are framing a deck or a floor system, you will need a rim joist to attach the joists to each other and spread the weight. It is essentially a piece of wood that connects to other joists to create a stable structure. It is located under the subfloor and connects the different floor joists. Plumbing pipes often run through it.

Joists distribute the weight of the building consistently across the entire building and hence it is an extremely important part of building construction. If you are planning to build a huge house, you will need many joists to erect it. Joists are the main structural elements when you want to build the floor frame of a house.

They are a structural element of a building. Without it, the building would collapse as it wouldn’t be able to hold the weight.

What is a rim joist on a deck or basement?

Rim joists need to be very strong as they are the final joists that end the series of framing joists. Since it is the main joist that supports the majority of the weight from the walls of the building, there should not be any faults while designing the rim joists.

A rim joist is an end joist that rests on the end of the structure. Since they are made of wood, the wood needs to be treated properly so that it does not start rotting inside. Make sure that you only use wood that is properly marked and rated for your requirements. Wood can sag if it is not strong enough and this can lead to cracks or even collapsing walls.

Rim joists are quite big and heavy. This is why multiple workers generally work together to carry them. It is important that they are installed level and that they are properly connected to the other joists.

They are used in the foundation of a home, addition, or deck. The advantage of using this type of construction is that it is fast to install and can last a long time. Another approach is to use a concrete floor plate. Concrete is heavier though so it is not always possible to use this.

Why do we need rim joists?

Rim joists provide support to the other joists. They also cover the ends of other joists to close the joist cavities which might come in contact with water and start rotting. Since rim joists are made of wood, nails can be inserted into them easily. Hence while installing the exterior wall sheathing, the masons will dig nails into the rim joists.

You may choose to use the conventional material for joists and most of the time the sizes are 2 x 10s and 2 x 12s. Solid framing lumber is the ideal material for constructing the rim joists and other joists. Lately, building constructors are also using laminated wood or engineered wood for constructing joists. Since the entire structure is dependent on the rim joists, we would never advise doing cost-cutting for the materials used for them.

You can buy tiles, bathroom fittings, etc. at an affordable price range because they can be changed later. However, joists, cement, and mortar for the building structure, steel bars, etc. are the main ingredients used to erect the structure. Having poor quality lumber for the joists might prove dangerous in the future.

If you live in an older home, it can be a great idea to inspect your joist regularly. They hold up the floor and if they break, your building can collapse. Home inspectors often spend a lot of time checking the quality of the joists. They can deteriorate over time or some insects can get into them. Replacing a rim joist is not an easy task so a lot of time is spent on checking this when a home is being inspected.

Using Rim joists for insulation

People who are looking at reducing their energy bills should think about insulating the rim joists. Talk to your building contractor about this option and he will advise about the ways to cover the interior face of the rim joist to cover with insulation. The goal is to make sure that cold air can’t spread in your home. Adding some insulation can make a big difference and make your home more energy-efficient. This way you don’t have to use your heater that much.

You can use foam and chalk to do this yourself. This can make a big difference already. Contractors are able to use more advanced materials to get an even better seal.


Architects and engineers spend a lot of time designing the best building possible. Rim joists are often an essential part of this as they help to make buildings stronger by spreading the weight. They avoid cracks in walls and make sure that buildings can last a long time. It is essentially a piece of wood that holds other joists together. They are often used for decks and home additions.

Rim joists are quick and easy to install. They also can last a long time. This is why they so popular. Plumbers often have to drill in them to install or fix the water pipe.

It is important to seal and insulate joist properly as a lot of cold air can come through this.




What Is A Rim Joist?