DIY: Tips for Installing Joists

DIY: Tips for Installing Joists

Courtesy of Smartnail

This do-it-yourself article features some key definitions about joists and their installation. We will provide details on some of the different types of joists, as well as best practices for the tools and fasteners to install them. Floor or deck joists are key for starting well from the ground up for any DIY person taking on this construction challenge.

What are joists?

Joists are an essential part of the frame for a house, deck, or another type of building. All joists are spread horizontally over a space, generally between beams. The beams transfer the load from the joists to the vertical structural members like a stud or truss. In a floor or a deck the joist will bear the contents (people and furniture) of what is on top of them. A ceiling joist is similar except that it does not necessarily support a floor, while a floor joist supports both the floor and the vertical structure.

All joists help distribute the loads placed on them. For example, when a load is placed upon a deck surface, the wood fibers on the bottom of the joist go into tension, while the top ones move into compression. This interaction between the fibers is what spreads the load out uniformly. It is important not to get joists and beams confused. A beam exists to support joists and there is generally one beam supporting several joists. In the picture below, you can see the beam going across the house, while the joists are leaning on top for support.

A floor joist diagram indicating the parallel floor joists resting on top of a support beam.

What are the different types of joists?

Joists can be identified by their purpose and the type of material they are made with. Like most topics in construction, there is a great deal of variability. Some common types of joists are ones we’ve already mentioned. For example: deck, floor, and ceiling joists are three common purposes. In the case of floor joists, there is even more variation.

Three common floor joist types are solid lumber, I-joists, and open-web floor trusses. The materials can be somewhat different between these three sorts. Solid lumber was the original type of joist and they can be economical depending on the type and grade of the wood being utilized. These joists tend to survive well in flooding and fire compared to other types, but you have to make sure to follow building code for notching, drilling, etc. when you want to run utilities through. The I-joist is a type of engineered wood that can span longer distances than the solid lumber. They are made with materials like OSB which can make them more environmentally friendly than their counterparts. I-joists also have the least flex of the joist options, making them a good choice for heavy flooring like tile. Open-web floor trusses are made with 2x4 boards for the top and bottom with a lattice or web of diagon boards in the middle, held in place by metal plates. This makes it very easy to run electrical or HVAC through them.

How to install joists?

One of the first things to figure out is how far the joists will be reaching. This is known as the span. Generally, the larger the span, the larger the joist which makes sense since it will be supporting weight over a longer distance. The grade and species of your lumber material will also affect your maximum span. You also need to consider the spacing between the joists. They are installed parallel to each other at the same interval, most commonly 16 inches apart from the center. This article provides some great tips and includes tables for different types of joist spans.

Once your span, spacing, and type of joist are determined. The next step is to consider how they will be fastened. If they are floor joists, you may be attaching to a rim joist or a sill plate. If a joist is installed above a foundation wall, a piece of solid lumber (sill plate) is fastened to the concrete with the joist nailed on top. Often your joist will require support beams when spanning longer distances. When fastening them to the end or a support beam, you’ll probably want to use a joist hanger (pictured below) which attaches the joist to the beam/sill plate through the joist hanger.

A standard metal joist hanger for framing construction

Make sure the joist hanger matches the size of the lumber for the joist. You don’t want to use a 2 x 6 hanger on a 2 x 10 joist and you also want to ensure that the fastener you use is not too long. The nail should not be so long that it is poking through the other side of the joist. Where the joist is being attached also impacts your selection of hanger nails. If you were attaching to a wall ledger, longer nails help with a better connection to the vertical structure. Talk to your Smartnail professional to make the best choice for your construction project. Joist hanger nails can be installed manually with a hammer, but if you wanted to speed up your process with a powerful punch, we recommend using these Metabo joist hanger nails which come in a strip for use with a framing nailer like the Metabo NR1890DCS Cordless Framing Nailer

Metabo HPT Framing Nailer for attaching joist hanger nails




Installing joists is a substantial do-it-yourself task, so be sure to talk to your Smartnail professional before starting the process. In this brief article we provide some explanation about what a joist is and the different types of joists you may use in your project. When it comes time to look at installation, knowing the span and the type of joist material will help determine where support beams are installed. Using joist hangers is a must and it is important to choose the fastener that is strong enough to do the work and the correct length for the job. As always feel free to reach out to us by phone, email, or visiting the best source of fasteners in London, Ontario!