The design of the sliding support for rafters is an important consideration when building or remodeling a roof because it guarantees structural longevity and integrity. This part helps with adjustments to account for things like weather variations and settling in addition to supporting the weight of the roof.
The purpose of sliding support systems is to preserve stability while enabling some rafter movement. This flexibility is crucial because it guards against structural damage from temperature variations, settling of the building over time, and expansion and contraction brought on by these factors.
One of the main advantages of sliding supports is their capacity to lessen the load on the rafters, increasing the roof’s lifespan. These supports aid in preserving the general structural integrity of the building by lessening the stress brought on by external variables.
Materials like steel or engineered polymers, which are selected for their longevity and corrosion resistance, are frequently used in modern sliding support designs. These materials guarantee that the supports can endure the harshness of different weather conditions for a long time in addition to providing strength.
| Design Feature | Description |
| Adjustability | Sliding supports allow for movement and adjustment, accommodating changes in the roof structure. |
| Material | Typically made of steel for strength and durability. |
| Installation | Can be easily installed during the roof construction process. |
| Flexibility | Helps in distributing loads and preventing structural damage. |
| Cost | Cost-effective solution for providing support to rafters. |
The need to use sliding supports
It is not always necessary to firmly fasten the rafter legs with brackets, nails, or other fasteners to the ceiling beams or Mauerlat. It is advised to leave room for rafter legs to move in relation to the support if the building’s box is prone to shrinking.
Historically, a strong, twisted forged wire was used for this. It allowed for a certain amount of structural element freedom while also providing a dependable connection between the rafters and the upper crown of the log house. These days, a sliding support—a specially made fastener that is dependable, long-lasting, and simple to install—is utilized for this purpose.
First and foremost, when building a wooden house, the free stroke of the rafter beam at the mounting point to the support (overlapping beams or Mauerlat, the function of which is performed by the upper crown of the log house) is required. The type of material used to construct a structure and the moisture content of the wood affect how much they shrink.
It might be:
- a log chopped;
- log -looped;
- whole beam;
- The beam is glued.
Walls composed of whole wood that has been exposed to natural moisture are significantly more distorted than glued beams, which are least prone to shrinking. Over the course of the year, the log house beneath the roof may drop by 15%. Remember that shrinkage typically happens unevenly, which can cause the rafter system—which is firmly fixed on the ceiling beams or Mauerlat—to seriously deform.
Roof skew can also develop while the structure is in use. The wood swells during the rainy season due to increased humidity, and the log house’s geometric sizes fluctuate throughout the winter as a result of the wood’s natural moisture loss and drying out.
The rate at which the house’s walls set or lose moisture varies concurrently with the amount of light they receive from the sun and rising winds. If the log house has a central wall that supports the ceiling beams or the high-speed run, keep in mind that this wall is also prone to changes in temperature and humidity, and the amplitude of these changes differs greatly from the indicators of the outer walls. For example, the central wall becomes significantly drier as the house warms up.
The weight of the load, including snow, can cause the logs in the upper wall of a wooden log cabin to bend outward due to horizontal pressure if the rafters are fastened tightly to the Mauerlat (upper crown).
Another issue to consider is that the length of the beam (boards) will decrease as they dry out if the rafters’ material was not mechanically dried.
In this instance, the roof is significantly distorted due to the rigid attachment of the rafter legs to the log house, which will have an impact on its functional properties.
A unique mounting node design at the locations where the rafter legs conjugate with the walls is made possible by avoiding such challenges. The roof can move without altering its geometrical specifications thanks to special fasteners.
Understanding the essential elements that guarantee structural integrity and functionality is essential when designing sliding support for rafters. By allowing for thermal expansion and contraction, these supports promote mobility and avert structural deterioration over time. They keep the roof stable in a range of weather conditions by permitting controlled sliding along fixed points. This article examines the design ideas underlying sliding supports and emphasizes how they improve the robustness and efficiency of roofing systems.
Sliding support: design features
The rafter leg can be fixed on the Mauerlat or overlapped with reliability thanks to the sliding support, which also gives it the freedom to move along its own axis at a predetermined distance.
There are two components to this fastener:
- guide (metal bar, which is attached to the rafter);
- A corner with a supporting platform (mounted on a beam of ceilings, Mauerlat or upper crown).
A loop that is attached to the guide is located in the upper portion of the corner. A constructive solution like this gives the rafter some freedom in one direction and a strictly limited range of travel, which is based on the guide’s length.
There are two types of sliding supports: closed and open. There are two distinct components to an open-type design. At each end of the steel curved plate (guide), there are two or three fasteners. There can be up to five holes in the support site for the stationary portion (corner).
Depending on the model, the fastening course’s length can range from 60 to 160 mm. The Kucis brand sliding supports with stroke lengths of 90, 120, and 160 mm are among the most widely used options.
The unsightly closed sliding support is installed in a fully assembled state. Its stationary portion consists of a corner with a holder accessible through its extended side.
The rafters’ sliding support is made to work in challenging circumstances where the structure must withstand heavy loads and moisture damage from condensation or water that has fallen through the roof’s slope.
The steel used in the production of sliding supports must have a minimum thickness of 2 mm. Generally speaking, the plates are 40 mm wide and 90 mm tall at the corner.
Low-carbon steel is usually used as raw material because it is easy to process and has a low percentage of carbon. The deoxidation method is used to increase the product’s strength characteristics. Cold stamping technology is used in the production of goods. We can avoid premature fastener destruction by processing the material with hot galvanizing, which ensures corrosion protection.
To prevent rusting, it is advised to coat a sliding support with oil paint prior to installation if the material does not have a factory-applied galvanic protective anti-corrosion coating. It is essential to use corrosion-resistant screws when installing sliding supports because fasteners without a protective layer will break down rapidly and destroy the roof.
Installation of sliding supports
Wooden rafter supports can be affixed one at a time or in pairs, one on each side of the rafter leg. If the building is being done in an area with little snowfall and wind, and the roof structure has a relatively small mass, the second option is utilized. In other situations, mounting mounts on both sides of every rafter is advised.
The smooth platform needs to be cut if the rafter leg is mounted on the upper crown’s round log, beneath the sliding support’s stationary portion, rather than a Mauerlat or ceiling beam.
The size of the M-shaped portion of the sliding support should match the width of the site. This will secure the mount to the base with reliability.
The sliding support ought to be installed so that the rafter can freely move in the direction of its axis’ location.
Cuts in the Mauerlat can be made to accomplish this, acting as guides and preventing the structure from skewing. After all of the skate’s rafter legs are connected and the props are manufactured in Mauerlat, the sliding supports installation process starts.
The Kucis (or other brand) sliding support’s length is chosen based on the estimated parameters of the rafters’ displacement during shrinkage and temperature-humid vibrations of the house’s walls. It is crucial to keep in mind that the inspection in the Mauerlat shouldn’t go deeper than 3/4 of the way down, as this will severely weaken the roof’s design.
Installing the guide bar on the rafters is the first step in installing a sliding support. It needs to be positioned parallel to its ribs and fastened firmly with self-tapping screws covered in a covering. Next, a fixed corner is installed. Since the rafter beam lowers as the house shrinks, the corner loop’s starting point is at the bottom of the guide bar.
The support site needs to be precisely perpendicular to the rafter leg’s axis.
The sliding support’s components cannot freely move in relation to one another when it is installed incorrectly, and the resulting friction may cause the fasteners to be overused or damaged, which could jam the plate or cause the corner to separate from the crown.
Anyone working on roof construction must comprehend the layout and operation of sliding supports for rafters. These supports offer a versatile solution that takes into account a building’s inevitable movement brought on by temperature variations and settling over time.
Rigid connections can cause structural damage; sliding supports stop that by letting the rafters expand and contract. This adaptability increases the roof’s lifespan and guarantees stability in a range of weather scenarios.
Rollers or brackets that enable seamless movement along the support beams are essential parts of sliding support systems. In addition to supporting the rafters, this design makes maintenance easier by providing simple access for inspection and repairs.
Careful planning is necessary to ensure that sliding supports are compatible with the materials and design of the roof. To maximize performance and longevity, factors like load-bearing capacity, environmental factors, and roof pitch must be taken into account.
All things considered, sliding supports for rafters are a contemporary method of building roofs that place an emphasis on robustness, adaptability, and simplicity of maintenance. These systems can lower long-term maintenance costs and improve a building’s structural integrity.
