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When building a new home or renovating an older one, many homeowners choose to upgrade the structure’s foundation, or the structure itself, by adding a bar joist. A bar joist is a structural member used to support the weight of a ceiling or roof.  

The right material for a bar joist is important, as it will support the weight of the roof and limit the movement between the walls and the ceiling. Choosing the wrong material can lead to a ceiling collapse or other structural issues. 

Every building requires a specific set of materials to be built, which is why it’s so important to choose the right material for the job. Most materials are specified by their weight. The more weight a material has, the stronger it is. However, the right material for the job doesn’t always mean the heaviest.  

metal bars for home's bar joist system

What to Think of Before Choosing a Bar Joist System 

Estimated Weight It Will Support 

Building contractors must think of the estimated weight that the joist system will support. That includes building materials, people working on the roof, and furnishings. It is important to calculate the load the joist system will support to ensure that it is strong enough to hold up during your construction.  

You should use a joist system based on the weight of the building materials, plus 5% to 10%. The weight of the building materials is the amount of weight the joist system will support, minus 2% for people working on the roof, plus 10% to cover furnishings (e.g. ceiling fans or air conditioners).  

Required Span 

How far the bar joist system must be from the wall for support is also a factor homeowners think about. The longer the span, the greater the joist system’s stability. Be sure to consider the space between the joist and the wall, as this is the zone of risk.  

A joist system is designed to support the roof and limit the movement between walls and ceilings to promote safety and longevity. It’s important to balance the weight of the bar joist system vs. the distance between the wall and the ceiling. You should be sure to factor in a safety margin of 10% to 20%. That should allow you to install the bar joist with ease. 

Building Design 

Bar joist systems are usually installed in a rectangular building, where the joist runs from the header to the sill. The height of the bar joist system should be at least 3 feet off the floor and at least six times the span. Homeowners often overlook this rule, which leads to some major problems.  

Before installing a bar joist system, you should check that the roof is structurally sound and that the walls are necessarily safe. You should also ensure that the joist system will not interfere with plumbing, electrical, or plumbing fixtures.  

Local Building Code Requirements 

The National Association of Home Builders (NAHB) has a set of requirements for bar joist systems. The most important of these requirements is that a building inspector inspects the bar joist system before installing it.  

If you live in a state with no local building code, you will have to consult a building or structural engineer, architect, or local building inspector to determine what is and isn’t allowed. It will help if you get the proper permits before installing a bar joist system.  

builders working on a bar joist system

Ready to Build Your Home with Bar Joist Systems? 

Bar joist systems make it easier to support and design your building, but they can be difficult to install. To learn more about bar joist systems, call us at Miami Metal Deck, and we will be happy to help.