Everything You Need to Know About Roof Trusses

Roof trusses are a crucial part of any building's structure, providing support and stability to the roof. They're typically made from wood or metal, with wood being the most common choice.

A standard roof truss consists of a series of triangles that work together to distribute weight evenly. These triangles are formed by the truss's rafters, which are the sloping sides, and the truss's webbing, which connects the rafters together.

Roof trusses can be custom-made to fit a specific building's design, but they can also be pre-fabricated to save time and labor. Pre-fabricated trusses are often used in mass-produced homes and buildings.

The strength and durability of a roof truss depend on the type of materials used, as well as the truss's design and construction. Wood trusses, for example, can be prone to rot and insect damage if not properly treated.

Recommended read: Wood Roof Truss Design

A roof truss is a triangular structure that makes up the framework of a roof, typically consisting of a series of rafters and a web of support beams.

Roof trusses come in a variety of types, including howe trusses and scissor trusses, each designed to meet specific building needs and codes.

They are often prefabricated to make installation easier and faster, and can be made from a range of materials, including wood and metal.

A roof truss is a pre-fabricated structure made up of several wooden or metal members that are designed to support the weight of a roof.

Roof trusses are commonly used in residential and commercial construction because they allow for faster and more efficient building of a roof.

A typical roof truss consists of a series of triangles that are connected by beams and rafters.

The triangles in a roof truss are designed to provide a strong and stable base for the roof, while the beams and rafters provide additional support and help to distribute the weight evenly.

Roof trusses can be made from a variety of materials, including wood, steel, and aluminum.

They are often manufactured in a factory and then transported to the building site for assembly.

Roof trusses can be customized to fit specific building designs and sizes, making them a versatile option for builders.

Worth a look: How to Support Roof Purlins

A roof truss is a great way to go, and here's why. They're significantly cheaper than traditional rafters, saving you up to 30% on costs.

One of the main reasons trusses are more affordable is that they use lighter materials and can be produced in large quantities. This drives down the price, making them a more attractive option for homeowners.

You can expect to spend anywhere from $50 to $450 per truss, depending on the design and materials used. This is a fraction of the cost of traditional rafters, which can be a game-changer for your budget.

Truss designers use computer-aided design (CAD) software to create precise designs that meet specific loading and spacing requirements. This ensures that your trusses are tailored to your home's unique needs.

With trusses, you can enjoy easier electrical, plumbing, and HVAC installations, thanks to the precision cutting and uniformity of the design. This makes the installation process smoother and more efficient.

Using a reputable truss manufacturer can provide added peace of mind, as they often offer certifications and warranties that meet or exceed industry standards.

Truss systems can also distribute the weight of the roof onto the exterior walls of the house, eliminating the need for interior load-bearing walls. This creates more open space and makes it easier to design open-concept living areas.

Here are some additional benefits of trusses for homeowners:

There are several types of roof trusses to choose from, each with its own unique characteristics and uses. King post trusses are the simplest type of truss, made with just a few materials and a straightforward design, but they can only span short distances.

King post trusses are best suited for smaller projects like home additions or garage construction. They are also the most affordable option, making them a great choice for those on a budget.

Here are some of the most common types of roof trusses:

These are just a few examples of the many types of roof trusses available. Each one has its own strengths and weaknesses, and the right choice will depend on the specific needs of your project.

King post trusses are the simplest roofing truss. They're made with just a few materials and a basic design, which makes them easy to construct and affordable.

King post trusses use the fewest truss members - two top chords, one bottom chord, a central vertical post called the king post, and two webbing chords. This simplicity also means they come at a lower price point than many other trusses.

King post trusses can't span long distances, so they're better suited for smaller-scale projects, such as home additions or garage construction, with a span of 16 to 26 feet.

They're a popular choice for homeowners seeking a balance of functionality and aesthetics, and their unique design adds visual interest to both the roof and interior.

The Pratt truss is a simple yet sturdy design that's perfect for structures with mainly vertical loads. It's made up of vertical and diagonal beams that work together to create a strong and economical roof truss.

The vertical beams are in compression, while the diagonal beams are in tension, making it a great option for covering longer spans. Pratt trusses are also lightweight and distribute forces evenly, making them a great choice for buildings with smaller cross-sections.

One of the best things about Pratt trusses is their affordability. They're a cost-effective option that's perfect for homeowners on a budget. They're also easy to install, which can save you time and money in the long run.

Here's a quick comparison of the Pratt truss with other types of roof trusses:

As you can see, Pratt trusses are a great option for covering longer spans, while king post trusses are better suited for smaller projects. Queen post trusses, on the other hand, are perfect for larger residential and agricultural construction projects.

Discover more: King Truss Roof

The Fink truss is a popular choice for residential projects, and for good reason. It's the most common type of truss seen in residential roof construction.

Fink trusses have a distinctive 'W' shape in their webbing, which gives them a great load-carrying capacity. This design also allows for some storage space, making them a practical choice for homes.

Fink trusses are considered one of the most cost-effective house trusses available, requiring a minimum amount of materials to provide strength and stability. They can even span long distances, up to 46 feet according to some sources.

One of the benefits of Fink trusses is their versatility. They can be adapted into other types of trusses, such as the Double Fink, and are ideal for short-span and high-pitched roofs.

Raised-Heel trusses offer a unique design that provides extra space for insulation, enhancing energy efficiency and reducing heating and cooling costs. This is achieved through an extended heel at the building's edge, creating a raised profile.

A key benefit of Raised-Heel trusses is that they simplify attic ventilation, preventing ice dams and making it easier to build and install with standard methods. This is a great choice for homeowners looking to improve energy performance.

The Raised-Heel truss design is particularly effective in residential construction, where it can lead to increased comfort and long-term savings. This is because the extra insulation space reduces heat loss in the winter and heat gain in the summer.

Here are some key characteristics of Raised-Heel trusses:

Raised-Heel trusses are a popular choice for homeowners looking to improve their home's energy efficiency and comfort. By providing extra insulation space and simplifying attic ventilation, they can lead to significant long-term savings.

Scissor trusses have a distinctive zigzag shape that creates visually appealing interiors. Their sloped design prevents water accumulation, reducing the risk of damage.

Scissor trusses are commonly used in residential roofs, and they're easy to repair and maintain due to their straightforward layout and marked joints. They offer customization options, adapting to various project needs.

One of the benefits of scissor trusses is that they eliminate the need for extra support, making them cost-effective. They can be made of timber or steel, and they're strong, stable, and versatile.

Scissor trusses can create vaulted or cathedral ceilings, making them a popular choice for homeowners who want to add some drama to their living spaces. The bottom chords of scissor ceiling trusses are sloped, creating the dramatic ceiling in the room below.

Here are some key characteristics of scissor trusses:

Mono trusses are a type of roof truss that's perfect for roofs sloping in one direction, often used in porch constructions.

They have an asymmetrical design that caters to specific architectural needs, offering both functionality and visual appeal.

These single-span trusses are strong and distribute loads evenly, making them ideal for industrial and commercial buildings.

Mono trusses are commonly found in extensions or modern builds, and are a cost-effective and efficient choice for roofs with a single slope.

Their spans range from 16 to 40 feet, making them suitable for a variety of applications.

Here are some common uses for mono trusses:

Mono trusses are also referred to as monopitch or monoslope trusses, and are a great alternative to a single truss when a long span is required.

Hip roof trusses are a popular choice for building projects. They provide strength and stability in high-wind areas.

One of the key features of hip roof trusses is their unique shape, with four planes meeting at the top to create a pyramid shape. This design makes them stronger and more aerodynamic than other roof styles.

A unique perspective: Types of Roof Shape

Hip roofs are found in both residential and commercial buildings. They offer more attic space than other designs, making them a great choice for homeowners who want to add dormers or extra living space.

Hip roof trusses can accommodate diverse sizes and styles, with spans between 24 and 60 feet. They're made of durable materials like wood or steel, ensuring reliability in construction projects.

Here's a quick rundown of the characteristics of hip roof trusses:

Overall, hip roof trusses are a reliable and versatile choice for building projects.

Flat roof trusses are a sturdy option for various constructions, from residences to bridges.

They're perfect for managing rain or snow runoff, and their design allows for efficient weight distribution.

A flat truss is a structure with horizontal top and bottom chords and diagonal members connecting them, forming triangles to efficiently support roof loads.

Flat trusses are commonly used in constructions that require a steep pitch in one direction.

Fan trusses are a great choice for large projects with spans between 33 and 49-feet.

They offer quicker construction due to their fewer parts, making installation a breeze. This is especially beneficial for homeowners who want to get the job done efficiently.

Homeowners should choose fan trusses for their ability to support long spans, giving them peace of mind.

Designing a roof truss involves assessing various loads that act on it. The wind load to be used for designing the roof truss members is specified in ASCE 7-16 LRFD Load Combinations.

To determine the loads carried by the roof trusses, we'll select Open-Pitched/Duopicth as the roof profile on the Structure Data tab. This is because the garage is not enclosed by walls.

The roof trusses will be analyzed using the SkyCiv S3D software, assuming a simply supported condition. The initial section used is an AISC L shape – 2.5”x2.5”x3/16”.

For more insights, see: Load Bearing Roof Truss

The dead load is calculated as follows:

For roof trusses, the superimposed dead load is calculated by multiplying the load by the spacing of the members. The results are:

Designing using SkyCiv involves providing specific information about the building and roof truss. This can include the location, building length, and width, as well as the eave height and roof truss height.

The location of the building is crucial, as it affects the wind load calculations. For example, the building in question is located at 8050 SW Beaverton Hillsdale Hwy, Portland, OR 97225, USA.

To design a roof truss, you'll also need to specify the building's dimensions, such as its length, which is 10.0m in this case, and its width, which is 7.0m.

The roof truss height is also important, and in this example, it's 2.0m. The roof angle is another critical factor, and it's specified as 29.745°.

The enclosure type is also relevant, and in this case, it's an open building. This information helps determine the wind load calculations.

To analyze the truss, it's necessary to isolate the critical truss and consider it as a simply-supported truss assembly. This can be done using an L shape (AISC) section for the roof truss.

Here's a summary of the key inputs for designing the roof truss:

Loads play a crucial role in designing a structure, and for a garage roof, it's essential to consider various types of loads.

Roof loads come in different forms, including dead load, live load, snow load, and wind load. For the garage roof, we'll be assessing the roof loads acting on the roof trusses.

The dead load includes the weight of the roof sheets and accessories, which is 0.15 kPa, and the ceiling, which is 0.25 kPa. These loads are applied at the top and bottom chords, respectively.

Expand your knowledge: Garage with Shed Roof

To calculate the superimposed dead load, we use the spacing between the roof trusses, which is 3.33m. This gives us a dead load of 0.5 kN/m at the top chord and 0.833 kN/m at the bottom chord.

The live load for roofs is 0.96 kPa, and since we're applying it to the top chord, we multiply it by the member length, resulting in a live load of 3.197 kN/m.

Snow load is another critical factor, especially for garages in open spaces. We'll be using the "Calculate Snow Load" parameters to determine the balanced and unbalanced snow loads. The balanced snow load is 0.23 kPa, resulting in a load of 0.766 kN/m on the roof trusses. For the unbalanced case, we get 0 kN/m and 1.399 kN/m for the two purlins.

Wind load is also an essential consideration, and we'll be using the SkyCiv Load Generator to calculate the wind loads acting on the roof trusses. The design wind pressures are calculated using the wind pressure calculation for components and cladding (Chapter 30 of ASCE 7-16). We'll have two cases: the positive (or max) case and negative (or min) case, resulting in wind loads of 2.168 kN/m and -1.508 kN/m, respectively.

Here's a summary of the loads we'll be considering:

K trusses are a sturdy and durable structural system that can efficiently carry significant weight, making them suitable for long-span structures with evenly distributed loads.

They consist of vertical and diagonal members, with shortened vertical beams that enhance resistance to flexural stresses. This arrangement reduces compression in vertical members, potentially lowering material usage and costs.

K trusses are a great option for homeowners who need to support long-span structures with evenly distributed loads, and their durability and affordability make them a practical choice.