What rafters are needed for a single -sided roof

Raffers play an important role in single-sided roof construction. The slanted beams known as rafters are what make up a roof’s structure; they support the roof membrane and distribute its weight against the building’s walls. Raffers are specifically responsible for supporting the entire roof structure of a single-sided roof, also referred to as a mono-pitch or shed roof.

Rafters are normally positioned at an angle and slope downward from one side of the building to the other in a single-sided roof design. Whether the roof covering is made of metal sheets, shingles, or some other material, these rafters are necessary to support the weight of the roof covering. Their slope makes it simple for snow and rainwater to slide off the roof, avoiding water buildup that may otherwise result in leaks or structural damage.

A single-sided roof’s rafter size and spacing are determined by a number of variables, such as the roof’s span, the weight of the material used for the covering, and regional building codes. In regions with high winds or loads of snow, rafters are typically placed closer together to ensure the roof can sustain these forces without collapsing or sagging.

It’s crucial to carefully determine the necessary rafter length, angle, and number when designing a single-sided roof. In addition to ensuring structural integrity, properly spaced and sized rafters also guarantee the roof’s long-term durability and safety. It is possible to make sure that the rafters are properly designed and installed for your unique roofing needs by speaking with a structural engineer or a licensed roofing contractor.

Features of the rafters for a single -sided roof

Let’s begin with the fundamentals. A single-sided roof only needs the house’s two walls for support. Just as she lacks a skate, she also lacks an intermediate node. This has the following three effects:

  1. The length of the rafters of the single -sided roof is almost twice as much as that of a gable.
  2. The slope of a single -sided roof is significantly smaller than that of any other pitched roof of the same width.
  3. When arranging a rafter system, intermediate supports are almost always needed: racks, decorative legs.

Also, each of these characteristics has an effect.

Extended length of the beams Finding and buying the right lumber for a single-sided roof is a very difficult task. Additionally, the composite rafter legs are already required if the slope is eight meters or longer.

A significant weight of rafters is an additional side effect in addition to these challenges. Everything about this is straightforward: mass increases proportionately to length increases within the same section. Working with such rafters is therefore difficult and occasionally impossible without the use of specialized equipment.

A more gentle slope also leads to problems. The smaller the slope of the roof, the higher the snow load on it. And this difference is tens of kilograms per unit area. In order for the roof to withstand the increased weight, you have to increase the cross section of the elements of the rafter system. Moreover, it is usually necessary to increase the thickness of the rafters of the single -sided roof, because their height is already so often maximum. And when working on bending, the growth of thickness is much less effective than an increase in height. Hence even greater weight of the rafters for a single -sided roof and increased requirements for the bearing capacity of the supporting walls and foundation.

There are significant limitations on the house’s design because of the requirement for intermediate supports. Racks ought to be supported by columns or walls that will help move the weight to the foundation. Large, roomy rooms are therefore more difficult to create in homes with single roofs.

For instance, the rafter system has two opposing walls as its only supports when utilizing a hanging scheme for rafter installation during the installation of a gable roof. Thus, the bearing walls within the house might not be. There are no essential limitations, so any arrangement of the living area is possible.

What are the rafters of a single -sided roof from

For a single-sided roof, there are four different kinds of rafters:

  1. Boards – Classics of rafter systems. Used in the vast majority of cases.
  2. Brick -is rarely used for rafters for a single-sided roof due to a large thickness. But if the maximum possible height of the boards (from available lumber) is reached, then to increase the bearing capacity, sometimes you have to replace them with a timber.
  3. Wooden I -beams – relatively new material, which is two timber with an OSB plate between them. The height of such beams reaches 450 mm with a weight of about 5 kg/m.P. This is the optimal material for the rafters of a single -sided roof, but it costs quite expensive compared to conventional lumber.
  4. Metal double -barrels and other metal rolling. Steel is heavy and expensive, but very durable. In addition, the use of metal rafters is the only way not to make intermediate supporting supports in large houses. After all, steel farms can easily rely on only two points.

The best materials for reasonably small homes with a slope length of up to 10–12 meters are boards and a beam.

In arctic conditions, metal is employed. The first choice is to construct very tiny structures, such as gazebos, garages, canopies, and verandas. In this instance, a far more reasonably priced profile pipe can be used in place of bulky and costly losers. The second option consists of very large cottages, the roofs of which are challenging to construct using alternative materials.

For medium-sized and larger homes, wooden I-beams are an excellent option. However, due to the limited number of manufacturers, they are not yet accessible in every part of Russia.

Choosing the appropriate rafters is essential when constructing a single-sided roof. These structural components bear the weight of the roof and distribute it to the building’s walls or columns. The rafters must be carefully selected based on the roof’s slope, the structure’s span, and the materials used to guarantee the stability and longevity of the roof. Knowing these factors can help guarantee that the roof not only endures the weather but also enhances the building’s overall appearance and functionality.

The dimensions of the rafters for a single -sided roof

Regarding the typical rafter size, it is the same for a single-to-shoe roof as it is for other pitched roof types. These measure 50 by 180, 50 by 200, and 50 by 200 mm. You can use thicker boards (75 mm) to increase the bearing capacity. Alternatively, a timber measuring 100 x 150 mm, 100 x 200 mm, 150 x 150 mm, 180 x 180 mm, and even 200 x 200 mm is already available.

However, when building a simple roof, it is preferable to determine which boards to use for the rafters of a single-tocate roof rather than depending on the standard sections.

Calculation of the cross section of the rafters for a single -sided roof

It is best to order the rafter size from a professional designer as it can be difficult to calculate for a single-sided roof. Thus, you probably achieve the best outcome. First of all, as an expert, the designer may recommend solutions that you are unaware of. Second, he’ll perform the computation more quickly and accurately.

But here’s the computation algorithm if you’re set on handling everything yourself:

  1. Choose the angle of inclination of the roof slope and the distance between the points of the rafters of the rafters – the working length of the rafter leg LMax. If the supports are planned to be arranged unevenly, a greater distance is taken. For example, if the rafter rests on the cornice Mauerlat, then after 6 m on the rack, and then after 9 m on the Mauerlat of the second wall, then LMax will be equal to 9 m.
  2. Determine the constant load on the roof. This is the sum of the masses of all components of the roof pie in the recalculation by 1 m 2 .
  3. We count variable loads. This is a wind and snow load, as well as a supply of roof service. Simply put, for the weight of the person who will walk on it. Also at the rate of 1 m 2 .
  4. Choose a step of the rafters A. Usually it is chosen from the range from 0.8 m to 1.2 m so that the whole number of rafter legs is placed in the slope.
  5. Fold the variables with constant loads and get the overall load Q.
  6. We transfer the total load to the area into a load per meter of the length of the rafters of a single -sloping roof Qr. This is done according to the formula: Qr= A · Q.
  7. Choose how thick the rafters are for a single -to -shuttle roof it is better to make. This parameter is indicated by the letter B and usually equal to standard values: 50 mm or 75 mm.
  8. If the slope angle is less than 30 °, we calculate the height of the rafter leg according to the formula: Hmin= 8.6 · lMax· √ (qr/(b · rhut)). In it Rhut – resistance to bend, which is taken according to table 3 from Section 6 SP 64.13330.2017 "Wooden structures" or from other standards.
  9. With an angle of inclination of a slope of 30 ° and the height of the rafter leg, it is considered a slightly different formula: Hmin= 9.5 · lMax· √ (qr/(b · rhut)).

Additionally, the minimum height needs to be rounded up to the closest standard board or timber size. It is preferred that the supply be between 100 and 150 mm.

After the initial computation, the outcome is frequently incorrect. For instance, the computation may indicate that you must use these kinds of boards—which are nonexistent in nature—for the rafters of a single-tocate roof. The process must then be repeated using different source data, reducing the step of the rafter legs, adding more intermediate supports, steepening the slope, and varying the board’s thickness.

The dimensions of the rafters on the plain roof need to be checked for bending after you have completed all the calculations and steps. The following formula is used to do this:

If inequality is implemented, all of your efforts were successful. If not, you must count the rafters and modify the criteria to make them more "loyal."

The length of the rafters

When using I-beam wooden beams, the maximum length of the rafters on a single-sloping roof is 12–14 meters. They can theoretically be made to order in longer lengths, but not all manufacturers offer this service.

If wood or boards are used, the length cannot be longer than 8 to 9 meters. Purchasing longer lumber is nearly impossible. Since the standard length is even shorter—6 meters—it is typically not possible to proceed without rafter fusion.

Steel rafters can be any length; their weight and load distribution plan are the only constraints. This is because metal parts just weld together.

Rafter Type Function
Main Rafters Primary support beams running from the ridge to the eaves, bearing the roof load.
Ceiling Joists Horizontal beams connecting the rafters, providing structural support and preventing the walls from spreading.
Cross Bracing Diagonal beams reinforcing the rafters, enhancing stability and load-bearing capacity.

The selection of rafters during the construction of a single-sided roof is essential for maintaining structural soundness and functionality. The slanted beams known as rafter support the roof and distribute its weight against the building’s walls. Certain types of rafters are required for a single-sided roof, also called a mono-pitch or lean-to roof, in order to achieve the desired slope and efficiently shed snow and water.

Common rafters are the term used to describe the principal rafters used in a single-sided roof. These rafters connect to the walls of the building at the eaves, which are the lowest point on the roof (ridge). They are essential for determining the roof slope’s angle, which is necessary for effective precipitation drainage. Common rafters serve as the fundamental framework for installing roof coverings and are frequently positioned uniformly across the roof.

When building a single-sided roof, additional elements like ceiling joists and ridge boards may be utilized in addition to standard rafters. In order to support the upper ends of the common rafters and stabilize the roof structure, ridge boards run horizontally along the peak of the roof. Concurrently, ceiling joists are horizontal beams that join the common rafters at their lower ends, adding to the roof assembly’s overall stability and strength.

The weight of anticipated snow loads, the type of roof covering to be used, and the local climate are all important considerations when designing and installing rafters for a single-sided roof. In addition to guaranteeing the roof’s strength and resilience, properly spaced and sized rafters also improve the roof’s overall appearance and ability to withstand different types of weather.

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Alexandra Fedorova

Journalist, author of articles on construction and repair. I will help you understand the complex issues related to the choice and installation of the roof.

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