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The structural integrity of a given building depends on a variety of factors, many of which rely upon one another for success. Roof trusses provide support for the roof itself, and a lot of that weight gets distributed to the exterior walls. Whether you’re building a new structure or renovating an old one, it’s important that these elements remain properly supported.
Since most exterior walls are load-bearing, traditional roof trusses don’t typically need additional interior load-bearing walls. The exterior walls bear the weight of the trusses, which are designed to stretch across the length of a building without the need for internal support.
Some larger or more atypical structures may require additional support somewhere, and there are different types of trusses that have their own requirements. In the remainder of the article, we’ll look more closely at what makes a roof truss stable on its own and how to determine if the structural components of your roof are sitting on a load-bearing wall.
Explanation of Roof Trusses
Due to their triangular shape, roof trusses are inherently rigid when connected at each corner. Additional elements get added to stabilize the structure and prepare it for the weight of the roof and potential snowfall.
The critical components of a traditional roof truss include:
- The bottom chord: This is the bottom piece of the triangle that stretches across the length of the building. The bottom chord absorbs the tension.
- The top chords: The top chords are the two angle pieces that come together at the top to create the peak of the roof. These pieces are under compression forces generated by the roof itself.
- Webs: The webs are the angle pieces situated at strategic locations within the triangle. They provide support so that the top chords don’t collapse from the pressure and may also absorb some of the tension along with the bottom chord.
- Nail plates: Nail plates are toothed pieces of metal that secure one piece of the truss to another. They’re most often present at the connection points between the chords and the web pieces.
Since the truss contains its own internal support structures and will rest on the exterior walls of the building, no internal load-bearing walls are necessary. A couple of the things that might make your trusses unable to withstand the load are improper calculations and poor build quality.
Today, most roof trusses are pre-assembled in a factory prior to being transported to the construction site.
While on-site assembly of trusses is still possible, this route increases the risk of error and may ultimately result in a less stable structure depending on the skill level of the assemblers.
Regardless, trusses are an extremely popular building method for new homes. They’re often cheaper than other options without sacrificing much quality.
What Is the Maximum Length a Truss Can Go Unsupported?
Roof trusses are specifically designed to remove the need for internal support, and their ability to span long distances is one of the major advantages. As a result, homeowners and business owners can create larger, uninterrupted work or living spaces.
Roof trusses can stretch 80-90 ft (24.38-27.43 m) without extra support in the middle. Longer trusses may incorporate steeper slopes or more internal webbing, among other things, to maintain stability.
Other considerations, like cost restraints and anticipated snowfall, are often taken into account when determining the maximum length of a truss on a given structure.
Longer trusses, particularly those in an industrial or commercial setting, may be built with steel rather than wood. Steel trusses, while more expensive, can handle greater loads and will last much longer.
At the end of the day, the maximum length for the trusses on one building won’t be the same as another, so it’s important to consult with a professional.
Identifying a Load-Bearing Wall
If you’re renovating and wondering whether or not you can remove a wall in the building, it’s important to make sure the wall isn’t load-bearing.
Although buildings structured with trusses typically don’t require that internal support, you shouldn’t assume the wall isn’t load-bearing before making the decision to remove it. Identifying a load-bearing wall isn’t always easy, but there are a few different ways. These are:
- The direction of the wall in relation to other elements of the house is an indicator. Walls that run perpendicular to the ceiling/floor joists are typically load-bearing.
- In multi-story buildings, load-bearing walls typically will stack on top of each other. If there’s a wall directly above or below the wall on the main floor, you could assume that they’re all load-bearing.
- Check in the basement or crawlspace for a support structure running along underneath the wall. This usually means that the above wall is load-bearing.
If you’re renovating the space anyways, you may be able to tear away the drywall or ceiling material to reveal the direction of the joists.
Alternatively, if you have wood floors, the direction of the flooring should be perpendicular to that of the floor joists. This doesn’t necessarily mean that the ceiling joists are running in the same direction, but it’ll at least give you a clue.
When in Doubt, Call a Professional
Whether you’re constructing a new building or renovating an old one, it’s important that you aren’t making decisions that might jeopardize the overall structural integrity of the building.
If you’re unsure about something, it’s always wise to consult with a structural engineer or relevant expert that can help you understand the many factors at play. If you’re renovating, for example, they won’t only identify load-bearing walls, but they’ll also tell if the wall is able to be removed and how to reinforce the space afterward.
On the other hand, new buildings and homes are huge, costly projects. Structural issues create major setbacks but might also lead to trouble down the road if not caught ahead of time. While trusses don’t require internal support walls, they must still have the appropriate support structures in place.
Since exterior walls carry loads, roof trusses do not typically need additional internal load-bearing walls, but you should be very aware of the way the exterior walls make contact with the trusses to be sure that the structure is stable. Roof trusses generally form a secure triangle formation that can stand on its own without the need for a supporting wall.
- Google Books: Ask the Family Handy-Man
- MAKE: How Do Trusses Work?
- Building Components Group: A Builder’s Guide to Trusses
- Wikipedia: Timber Roof Truss
- HITEK: 10 Reasons Why Roof Trusses Is Better Than Rafters for Your Home
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Giovanni Valle is an architect, designer, internet entrepreneur, and the managing editor of various digital publications including BuilderSpace, Your Own Architect, and Interiors Place. He is the founder of BuilderSpace LLC.