Although both techniques provide the same basic function, trusses are much stronger than rafters and joists. A roof truss can be described as a rafter, cripple, joist, and collar tie all in a single, preformed unit. Where rafters and joists are made on-site, trusses are built in a factory setting.
Full Answer
What are the main differences between trusses and rafters?
- Ridge Board: The ridge board must be the same width as the rafter boards. In heavy-duty construction, a ridge beam might be used instead.
- Collar Ties: These horizontally installed boards give the trusses strength and stability.
- Ceiling Joist: This board forms the bottom member of each rafter and, of course, the ceiling of the space below.
Why are roof trusses are more popular than rafters?
Roof trusses have become more popular than rafters in recent years for a few reasons. Perhaps the biggest reason trusses are more common is that they are over 30% cheaper than rafters. They use lighter materials and are able to be produced and purchased in large quantities, driving down the price.
Is there difference between rafters and truss?
Though both rafters and trusses are triangles in shape, the trusses have more triangle webs inside the principle frame. Rafters consist of sloping outer beams which provide support. As the trusses come with a web of triangles inside the main frame, they provide more support than the rafters.
What is the difference between ceiling joists and rafters?
Typically, the floor above is precarious -- a series of joists with nothing but wall sheathing on the underside, forming the ceiling ... joist as well. Measure and cut short blocks to run between ...
What is the difference between truss and rafter?
One of the main differences between truss roofs vs. rafters is the fact that trusses are prefabricated wooden structures while rafters are usually built on-site. For trusses, the triangular webbing of structural pieces not only provide support for the roof, but they also tie the outside walls of the home together.
What is the difference between rafter and joist?
The main difference between Joist and Rafter is that the Joist is a horizontal structural element transferring load from flooring to beams, typically running perpendicular to beams and Rafter is a structural members in architecture.
What is the difference between truss and joist?
The joist supports the load which the floor is built to bear. A truss is used to support the roof.
What's cheaper rafters or trusses?
Expensive - While rafters take less time to build and install, the wood and labor costs are more expensive than a roof truss system. Longer construction - Since rafters are built on-site and don't require any prior planning, they are more time-consuming, sometimes taking up to a week to complete.
Is a rafter a joist?
Are Rafters and Joists the Same Thing? No, but they do work together to provide support for a roof. A rafter provides the slope, or pitch of a roof and serves as a connection point for roof decking and shingles.
Can I joists be used as rafters?
Some builders use manufactured I-joists not only to support floors, ceilings, and flat roofs, but also in place of either sawn-lumber rafters or wood trusses to support pitched roofs.
Are trusses stronger than rafters?
Strength: On top of all the logistics of getting the trusses built, they are actually stronger than the traditional rafter system. This is because of the braces that the design includes, giving it a better weight distribution.
What is a roof joist called?
A rafter is one of a series of sloped structural members such as wooden beams that extend from the ridge or hip to the wall plate, downslope perimeter or eave, and that are designed to support the roof shingles, roof deck and its associated loads.
What is difference between beam and joist?
A beam is the main load-bearing structural element of a roof. It supports the weight of joists and other building elements. A joist is a horizontal member that generally runs across a building and is supported by a beam.
Can you build a roof without trusses?
It is possible to build a roof without trusses. In the past, roofs were often constructed without using trusses. Flat roofs or roofs with a single slope are built without trusses.
What are the disadvantages of roof trusses?
What are the cons of timber roof trusses?Timber can warp. In certain conditions, timber can change shape and slowly contribute to building damage. ... Timber invites pests. In certain localities, pests such as termites can present a risk to timber structures.
Are ceiling joists load bearing?
The term joist, in construction, usually means a horizontal load-bearing structural member, so ceiling joists are load-bearing.
What is a rafter roof?
Rafters are the traditional means of framing a roof. Building a roof frame with rafters is known as stick framing. This means that each rafter is built on the job site using dimensional lumber. Every piece is measured, cut, and fastened together to form the rafter. The stick framing process is labor-intensive.
How long is a truss span?
Truss spans can reach up to 60 feet. According to the American Wood Council, the maximum span for rafters is about 30 feet, and that’s with a relatively low load of 20lbs per square foot. As the load goes up for snow in northern climates or for heavy roofing material like tile, the span length decreases.
How long does it take to build a rafter roof?
And the roof is ready for the installation of shingles. On the same home, rafters might take a week to build, depending on the size of the crew.
Where are rafter boards fastened?
Rafter boards are fastened to the ridge board at the peak and the top plate where they join the wall. In finished space, insulation is placed between the rafter boards and drywall, or other material is fastened to the face of the boards. Ridge Board: The ridge board must be the same width as the rafter boards.
Is a truss better than a rafter?
It is certainly true that trusses are more commonly used than rafters. They’re more economical to build and offer the same or greater roof strength. There’s a lot to like. However, trusses don’t give you the opportunity for creativity in home design that rafters allow.
Do rafters have trusses?
It is common to read that “rafters are the way they used to frame roofs. Now everyone uses trusses.”. First, that is plain wrong, and an oversimplification at best. Secondly, rafters can have important advantages over trusses in certain building projects; If you’re planning for an out-of-the-ordinary, custom roof design or want to make use ...
Why are roof joists called roof joists?
So the only reason these planks are called roofing joists is because they run horizontally, or nearly horizontally, to the ground. Similarly, “ceiling joists”, are the planks of wood that create the flat surface of your attic floor, or top story ceiling.
What are roof joists made of?
Assuming that your builders have chosen to use wood for your house’s frame, your roofing joists, ceiling joists, rafters or trusses will be made from long planks of wood placed parallel to one another at evenly spaced intervals along the length of your roof.
Do you need structural support for a flat roof?
No matter whether you have a sloped roof or a flat roof, you will need some sort of structural support to hold up the weight of the roofing materials you or your contractors choose, and to connect the walls of your home and prevent them from spreading or racking.
Trusses vs. Rafters: The Main Differences
If you’ve ever seen a house’s framing or the structure underneath your own roof, you’ve seen either trusses or rafters. While trusses and rafters can both produce similar appearances in the roofs they support, they have very different functions and carry different results for roofing.
When to Use Trusses vs. Rafters
Rafters and trusses don’t just have different constructions from one another. One of the biggest differences between the two is their preparation and installation.
Other Considerations
The differences in trusses vs. rafters might seem numerous, but they have similarities that go well beyond merely supporting a roof.
Frequently Asked Questions
Here are answers to some of the most frequently asked questions about trusses vs. rafters.
So How are Trusses and Rafters Different?
Trusses are prefabricated roof structures that are easy to install on most buildings with sloped roofs. Rafters are boards that are typically wider than those used in trusses, are cut and installed individually at the job site, and run from a central ridge to the outside walls of the building.
What is a rafter in construction?
Rafters attached to ceiling beams. Joists and rafters are components used in the construction of buildings. Understanding the difference between them is essential for those working in the construction trades, while basic knowledge is useful for homeowners if repair and maintenance issues arise.
What is a timber joist?
Joists are the parallel horizontal beams that run across an open space, joining opposite walls in a building to support both the ceiling below and the floor above. Joists are traditionally made from timber. They are nominally 2 inches thick (actual width usually 1-1/2 inches) and come in a variety of widths from 8 to 12 inches.
How thick are rafters?
Rafters form the foundation for attachment of the roof boards, onto which the final roof covering is fixed. In traditional timber, they are nominally 2 inches thick and typically 8 to 10 inches wide.
What is prefabricated roof truss?
In many modern construction projects, prefabricated roof trusses are used. These triangulated structures, with a high degree of strength and stability due to the geometry used, form both the joist and rafter components of a building. These structures are typically manufactured offsite to a detailed plan and delivered complete, which helps to speed construction.
What is I profile beam?
In many modern building projects, traditional timber joists are replaced by ones manufactured from alternative materials. Steel "I-profile" beams are used in the construction of steel-framed buildings. These have the advantage of spanning greater distances without bowing. Timber "I-joists" are also available.
What is a joist vs a truss?
Joist vs. Truss. Joists are used in floors and as column support. The joist (also called Bandsill) supports the load which the floor is built to bear. It is like the skeleton a building. Trusses are of many types; the simplest is a planar truss which is used as a roof support system.
What makes a truss an efficient structural form?
The depth of a truss, or the height between the upper and lower chords, is what makes it an efficient structural form. A solid girder or beam of equal strength would have substantial weight and material cost as compared to a truss.
How deep should a joist be?
A rule of thumb for calculating the depth of a wooden floor joist for a residential property is half the span in feet plus two inches; for example, the joist depth required for a 14-foot span is 9 inches. The depth of a truss, or the height between the upper and lower chords, is what makes it an efficient structural form.
Rafters vs Trusses: Everything You Need to Know
If you have ever wondered what the difference is between a rafter and a truss, you’ve come to the right place. Both rafters and trusses can form the framework of a roof system, but they can be used very differently.
Do Rafters and Trusses Do the Same Thing?
In a sense, yes, rafters and trusses have the same purpose. However, while trusses can essentially stand alone and perform their function, rafters only make up one component of a roof system. Rafters establish the angle of the roof, which is expressed as a ratio of height to length.
What Are the Advantages Of Using Rafters?
Rafters have the advantage of being customizable on site. During normal construction, professional builders are primarily interested in speed while maintaining quality construction. As such, most will employ trusses wherever possible. It should be noted however, that trusses are not adjustable.
What Are the Disadvantages Of Using Rafters?
Building rafters and other roof components by hand is the traditional method of constructing a roof system. However, this process can be slow and require much more skill and experience than installing trusses.
When and Where Would I Use Rafters?
In the vast majority of applications, rafters are used to either solve a complex support concern or when an existing structure is being modified. For example, most new construction projects will employ trusses because the structure only needs to support its own weight.
What Are the Advantages Of Using Trusses?
Trusses are fast to install, do not require advanced skills, and can be designed for most applications. This is why the vast majority of new homes are built with trusses. In fact, trusses can also be (and often are) used to build the floor system as well. Roof trusses depend entirely on their design for strength.
What Are the Disadvantages Of Using Trusses?
As mentioned previously, one disadvantage of trusses is that they cannot be modified on site. Trusses depend entirely on their design, so if an installer were to trim or otherwise modify a truss it would no longer support its weight, nor pass most building inspections.
What are Rafters?
Rafters are the slanted beams that attach to your home’s walls at one end and to the ridge of the roof at the other. They support the weight of your roofing material like tiles or shingles.
Where Are Rafters Used Best?
Rafters should be used in areas that aren’t affected by snowfall or other types of severe weather conditions like hurricanes and earthquakes, but still experience strong winds.
What are Trusses?
Trusses are prefabricated wood or metal structures that act as the framework to support your roof.
Where Are Trusses Used Best?
Trusses are great for areas that experience heavy snowfall or hurricane-grade winds.
Which is Better? Deciding Between Rafters Vs Trusses
Trusses win out as far as convenience goes, but you need to take into account whether this will be worth it for you.