If you are a citizen and you live in a big city with bridges and skyscrapers, you probably have noticed that trusses are a critical engineering feature in civil engineering and construction. Roof trusses, bridges, electricity and telecom towers and even structural frames are making use of trusses as their integral structural forms!
Today, we will tell you more about trusses and house truss designs, in particular. You will learn what trusses are and what they are made of. Also, we will tell you what pros and cons trusses have depending on their material and what they are used for in construction. Finally, you will discover the major types of trusses that exist. This will help you better understand what they are and what benefits they give to buildings and other engineering objects.
What Are Trusses In Construction?
We are sure that all of you have seen trusses many times! So there is no need for a detailed definition. However, we will still remind you briefly of what they are. Simply speaking, a truss is a structure that consists of elements connected at pin joints or nodes. Trusses use triangulations to connect their parts mostly since triangulation is the most stable configuration mathematically. As a result, it allows making the stabilized structure.
Mostly, trusses are made with steel due to the strength and lighter weight of this material. However, over the past years and even now, trusses are also made with timber planks to enhance aesthetic features, not only the practical side. On the other hand, you will mostly see wooden trusses in residential construction.
Generally, a truss consists of the following parts:
- top chord
- bottom chord
- vertical chord
- diagonal chord
Since trusses are long-span structures with a relatively lighter weight, the demand for using them in the construction industry has grown significantly over the past decades. However, trusses are also widely used for home construction!
Here are the basic requirements that house truss designs must meet:
Dead loads for:
- The roof
- Chord or attic
Live load for:
- Roof live load per code.
Wind load per code:
- Load combination using allowable stress design per IBC
If there is an attic, an attic load must include any load for:
- Mechanical and electrical loads.
If there is any storage space in the attic, a minimum is 20 psf. For livable attic spaces, the minimum live load must be 40 psf. Finally, if the truss is a floor truss, the live load must be 40 psf for residential, 50 psf for office space and 100 psf for commercial spaces.
What Are Trusses Used For?
Trusses are widely used in cities these days. For example, you can often see them on railway stations holding roofs and supporting bridges. Also, trusses are used in residential construction where they have aesthetical and practical meanings.
Even when made of steel, trusses are still less heavy than other metal constructions. Besides, they have very favourable strength-to-weight ratios. Thanks to this efficiency, they are well suited as roof and bridge structures.
Types Of Structural Truss Design
There are several standard truss designs for homes and other objects. The specific truss design depends on where the trusses will be used. For example, there are a variety of shapes, styles, and sizes of lumber trusses available these days. Each wooden truss design is specific and fits the type of loading that it will have to bear.
But besides a regular-shaped wooden truss, some of the most popular truss styles include:
- Scissors Truss. Its sloped bottom chord allows for more ceiling height on the floor below. This truss type is sometimes used for vaulted ceilings.
- Polynesian Truss. This is a dual-pitched roof truss that has two different roof pitches from heel to peak.
- Cathedral Truss. It’s mainly used to provide a partially vaulted ceiling.
- Gambrel Truss. Usually used in barns and other similar structures. It also can be used when building an attic space.
- Attic Truss. Provides storage space in the attic. The crucial defining feature of this truss type is that it uses a more massive and heavier timber bottom cord to carry the applied loading.
Of course, when you need to figure out what type of trusses to use for your construction project, it’s your contractor who defines the truss type that will be more suitable for the specific object. However, now you know at least some basics about the types of trusses! This way, you will be able to decide which one suits you more.
Steel Trusses vs Wood Trusses. Pros and Cons
As you already know, trusses can be made of steel or wood. Wood and steel trusses are equally strong and very quick to install. However, it is still essential to choose a suitable material for your truss to ensure it meets the requirements of your project.
There are several pros and cons to using steel trusses compared to wood trusses. Below, you can read about some of them.
- Steel trusses last longer than wooden ones.
- Steel trusses require less maintenance.
- There is no need for chemical treatments for steel trusses.
- Steel is more lightweight than wood.
- More expensive.
- Require more skill to install trusses.
This way, now you know what factors to consider should you need to decide what truss material to use for your home construction project.
Now you know a bit more about trusses in construction! We told you what trusses are and what they are used for. Also, you are now aware of the most popular materials for making trusses. You know what types of trusses exist and what makes them different. With all this in mind, you will better understand why trusses are not only aesthetically attractive but also have practical meaning!
This process involves covering the frame with sheathing, which is usually plywood or oriented strand board (OSB). Sheathing not only adds structural strength but also provides a surface for the installation of exterior siding and interior finishes.
It's important to hire experienced contractors for rough framing work to ensure the building is structurally sound and meets all building codes and regulations. Skilled contractors will take into account the environmental conditions in the area where the building is being constructed, such as wind and seismic activity, to ensure the building is capable of withstanding those forces.
Accurate measurements and precise cuts are crucial in the rough framing process to ensure that all structural elements are properly aligned and fit together securely. A well-built rough framing stage will provide a solid foundation for the rest of the construction process and contribute to the overall quality and longevity of the building.