Hanging rafters: overview of structures + scheme for installing hanging rafter systems

Both builders and homeowners should be familiar with the fundamentals of rafter structures when it comes to roofing. The efficiency and aesthetic appeal of hanging rafters set them apart from other types of roof framing systems. Hanging rafters create overhangs that protect the building and add to its architectural charm, in contrast to traditional rafter systems that rest directly on the walls.

Consider the inviting porch of a rustic cabin or the eaves of a charming cottage; these details are frequently maintained by hanging rafters. The main feature of hanging rafters is their capacity to protrude past a building’s outer walls, offering protection from the weather and a unique aesthetic element. Rainwater is diverted away from the building by this design, which also makes it possible to incorporate aesthetic components like fascia boards and soffits.

A meticulously thought-out procedure is required when installing hanging rafters in order to guarantee both structural integrity and aesthetic coherence. Usually, builders start by planning out the roof and figuring out the proper length and angle for each rafter. The horizontal purlins or collar ties that support these rafters and help distribute the weight evenly across the roof structure are fastened to the ridge beam at the top of the roof.

Knowing the advantages of hanging rafters can be instructive for homeowners thinking about building a new home or renovating their roof. In addition to serving as a practical means of shade and weather protection, hanging rafters greatly enhance a home’s overall aesthetic. These rafters exhibit the skill and attention to detail that can turn an average roof into a defining element of architectural beauty, whether they are utilized to build a comfortable porch or to extend eaves over windows.

Features of the design of the hanging rafters

Why are they called "hanging" rafters? Because they are completely dependent on the exterior walls and literally freeze inside the inter-sorcerer. Internal support does not exist. However, hanging systems can block spans of up to 14–17 meters because of their design, which prevents them from bending!

Naturally, hanging rafters are not utilized on their own; they are merely a component of the rafter system. Only when combined with additional components (grandmothers, crossbars, struts, etc.) do the rafters create farms or arches.

When it comes to hanging rafters, the most basic farm consists of two rafter beams joined at an angle (forming a triangle) at the upper point. A puff, typically a wooden beam, is used to secure horizontal rafters. However, it could be made of metal, such as profile metal. Such a puff is then referred to as heavy.

The tightening serves a crucial purpose. Sturdy rafters set into the walls and secured in the skate make an effort to spread out to the sides. Additionally, the tightening keeps them in place so you can keep the arch’s triangular shape. Horizontal efforts are negated and the rising spacer is not transmitted to the walls. Therefore, when using hanging rafters, only vertical efforts have an impact on the external walls.

The tightening may occasionally move higher, closer to the skate, rather than always being at the base of the farm. Which work needs to be done depends on the kind of arc design. In the event that the tightening occurs at the rafters’ base, it also functions as a floor beam beneath it. In order to arrange a floor with a fully realized ceiling height, it is convenient to place a tightening (crossbar) above the base of the rafter legs when installing the attic.

Grandmothers serve as suspensions and braces to support hanging rafters when the distance between walls exceeds 6 meters. However, the puff is made of two solutions rather than being solid.

With hanging rafters, there are numerous design possibilities. Think about each one individually.

Design #1. Triangular articulated arch

The most basic farm, shaped like a triangle. consists of the skate’s two rafter beams coming together. The horizontal beam supports the lower foundations. The tightening is fixed at the base of the "triangle". The height of the ridge in the structure must be at least one-sixth of the farm span in order for the system to function properly.

One could refer to this scheme as classical. The rafters in it attempt to bend and split to the sides, and the tightening holds them in place while applying stretching loads. Since the puff is not a loading element, a litter of metal rolling can be used in its place.

In order to lessen the amount of bending in the rafter beams, an eccentric cut-out knot is used. As a result, in addition to the anticipated bend, the bending moment of the opposite direction appears when exposed to the rafters of external loads (atmospheric phenomena, the weight of the roof, its own weight, etc. P.). This makes it possible to apply a smaller beam for rafters in addition to reducing bending deformations. As a result, this contributes to lowering construction costs.

Generally speaking, an attic is built using this type of hanging rafter design. In this instance, the puffers serve as the attic overlap beams.

Design #2. Armor artis with a grandmother

When more than six meters of spans overlap, a more intricate plan is required.

A lengthy tightening in such a system will encounter heavy loads and eventually bend under its own weight. The tightening is suspended to the skate to prevent deflection. How? Adding one more component: grandparents. A wooden block is acting as the suspension. The suspension is referred to as heavy if it is composed of metal. For these purposes, a standard metal rod is frequently used, and it is effective at stretching.

Thus, it is possible to maintain a long tightening and level its deflection with the aid of a bag of a bag. Simultaneously, the tightening itself consists of two components—beams that are fitted with one another in the structure’s center.

Although the grandmother’s design is straightforward, construction mistakes are frequently made to the device. The most crucial thing to remember is that the grandmother should only work on stretching, never compressing. It is not to be confused with the counter that rests on the cornice knot and the tights of the tights. The element will compress in this situation as opposed to stretching.

Because the grandmother’s device and the stand are so similar, confusion like this may arise. But like the idea of work, their goals are entirely different. Unlike the rack, the grandmother is not fixed in place with a puff. It is suspended on the cornice node, and the tightening is fastened to its lower portion using clamps.

The component pieces are typed to the necessary length, joined with an oblique or straight tangle, and fastened with bolts. The clamp joins the puff when it is suspended.

The proposed plan is appropriate for large-span industrial and agricultural buildings. Nevertheless, it is no longer in use and is regarded as outdated in its original form. However, its individual components are used with great success in the practice of building, in the creation of other kinds of arches.

Design #3. Hinge arch with raised puff

According to this plan, the puff is positioned higher and closer to the skate rather than at the base of the arch. It stretches more at the tightening installation site that is higher.

Attic rooms are built using the structure with the raised puff. How the tightening is highly located directly affects the ceiling height.

The structures’ rafter beams are not tightened; rather, they are based on Mauerlat. Furthermore, the fastening is flexible and slides in a slider-like manner rather than being rigid. It enables you to adjust for the variations in temperature and humidity that cause the beams’ size to change (their progress).

In any scenario, the system will be stable if a uniform load is applied to the slopes. The rafter system will move in the direction of the prevailing load if the load is greater on one side. The rafters are installed with removal in both directions, outside the walls, to prevent this and ensure the stability of the roof.

When the attic is arranged, stretching loads and stretched-beating act on the tightening in such an arch, which is not a support.

The tightening in the attic rooms is typically a beam to which insulation or a suspended ceiling is attached. Install the suspension to prevent it from sagging. The suspension is nailed to the skate and the cross with small purported loads, securing the connections with two boards on each side.

A number of pendants are used, each secured with nails, if the tightening is rather extensive. Clamps must be used in addition for large loads.

Design #4. Sharnic arch with rigel

A similar stiff is used in place of the lower sliding support in the cornice node in this diagram, which is similar to the previous one. Rafter beams with fixed fixation are either cut into a Mauerlat or use support bars.

The type of stresses that develop in the arch are altered when the support is replaced. The design shifts into a spacer, acting on the walls and Mauerlat with bursting efforts.

The upper portion of the arch is where the tightening is installed. In this instance, its goal is evolving. Her action is based on compression; she is no longer able to stretch. Rigel means pushing for compression.

The single-rigel raised arch is intended to support a light spacer load. A tightening is installed in addition to the crossbar when heavy loads are involved. The hanging rafters are acquired; their nodes and design resemble the typical three-haired arch. For them, Mauerlat is no longer necessary.

Design #5. Arc with a pendant and struts

Grandma adding to the arches in the scheme. It is employed in situations where the rafters’ length—up to 14 meters—causes a noticeable deviation in their own weight. The struts that support the rafter beams add to the system to help level out the bending stresses.

Struts typically rest against the inner walls. However, since they are not in the hanging systems, the grandmother serves as the sole point of emphasis for the struts. The result is a rigorous design that operates on the following principle: when an external load acts on rafters, they bend and press against the struts; the suspension stretches and draws in the ridge beam; the upper portions of the rafters also draw in the ridge beam; and finally, the rafters are packed with struts.

This scheme makes appropriate use of a long tightening because it uses long rafters. It typically consists of two beams joined in the middle of the span or direct otruc; however, it can also be composed of a single element. Using the clamp, the tightening connection with the grandmother is accomplished.

Actually, every hanging arch that is currently in use is a variant of the typical three-haired arch. Grandmas, crossbars, and struts are among the other additions that merely make the rafters more rigid. Furthermore, the bearing capacity remains constant.

"Knowing the structural importance of hanging rafters and the critical procedures for their efficient installation is essential to comprehending them. This article gives a thorough introduction to hanging rafter structures, describing their function in roofing stability and providing a simple, understandable installation plan. Both professionals and homeowners can improve their comprehension and method of incorporating hanging rafters into roofing projects by decomposing these ideas into manageable steps."

Main nodes: types of compounds of elements

Only when all major nodes are connected competently can any of the above-discussed structures function as intended. It is only then that they will perform their function without undergoing deformation due to external influences.

The rafter beams are joined at an angle from above and either overlap or are cut to connect to the water. Skate is the name of this knot. Docking the beams that have been chopped off at the ends’ corners is necessary for securing the VSTS. The upper portions of the rafter are secured to one another when the overlap is combined and fastened with a bolt fastened with a nut or stiletto.

In the same way, a gribly’s connection and the connection are similar. However, in this instance, the rafters’ tops are applied to one another after the excavations are reduced in half, resulting in half the thickness of the timber. After that, a through hole is drilled in each of the cut pieces, and they are joined and pulled together.

The connection between the lower part of the rafters and a tightening is also present in the arches’ structures (e.g., in the typical three-shaped arch). The head-shaped chipping with a single or double tooth and bolt fastening completes the connection. Short boards or metal plates can be used for fastening; they can be placed on the rafter joint, tightened, and secured with nails.

With the next bolt fastening, the raised puff is sliced into the rafters.

In the plan featuring an elevated rafter, the rafters are fastened to the Mauerlat. In this instance, the support is either hard-supported or sliding, depending on the kind of slider. With a sliding mount, the rafters can move slightly thanks to metal sliding supports. A cut tooth is used with hard mount, and a support bar is an option.

General principles for calculating hanging rafters

As you have successfully confirmed, the hanging rafter system pertains to intricate structures and necessitates accurate computation based on numerous variables. Inaccurate end parameters will cause the roof to become unstable and potentially collapse due to its inability to support loads.

As such, it is best to use the completed house project or leave the calculation of hanging rafters to the experts. There are a good number of online calculators available on the Internet for use in extreme situations.

The computation makes use of the following data:

  • the dimensions of the overlapped room;
  • the presence of an attic;
  • estimated maximum load;
  • the angle of inclination of slopes;
  • type of rafter system;
  • wall manufacturing material;
  • Roofing material.

Following the computation, they ascertain:

  • cross section of rafters;
  • the size of the step of the rafters;
  • Farm form.

Anyone working on roofing projects has to understand the installation and structure of hanging rafters. Rafts that are suspended, sometimes referred to as dropped or flying rafters, are an essential part of roof construction because they offer stability and support. Unlike conventional rafters, they extend past a building’s outer walls to form overhangs that both improve architectural design and shield the walls below from the elements.

Careful planning and execution are necessary when installing hanging rafters. To make sure the rafters are positioned correctly to support the weight of the roof and provide enough overhang, the process starts with precise measurements and computations. Usually, each rafter is cut to size, installed one at a time, and fastened to the roof’s structural framework. To guarantee the roof’s long-term durability and structural integrity, this installation technique calls for accuracy.

A hanging rafter system’s schematic diagram shows the parts and installation process. It illustrates how each rafter protrudes past the wall plate and is held up by cantilever extensions or purlins, which are horizontal beams. Together, these components evenly distribute the weight of the roof and give the overhang the support it needs. The illustration provides contractors and roofers with a visual guide that outlines the procedures needed to build a sturdy and useful hanging rafter system.

In conclusion, obtaining both visual appeal and structural dependability in roofing projects requires a thorough understanding of the concept and installation of hanging rafters. Builders can improve the functionality and aesthetic appeal of roofs while guaranteeing long-term weather resistance and durability by knowing their role and adhering to a clearly defined installation scheme.

Video on the topic

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Denis Shcherbakov

Professional roofer with 20 years of experience. I know everything about the installation, repair and maintenance of various types of roofs. I will be happy to share my knowledge and experience with you.

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