Snow weight per 1 m2

Maintaining the structural integrity of your roof during the winter requires that you understand the weight of snow on it. Various factors, such as snow density and moisture content, can cause significant variations in the weight of snow per square meter. It is crucial to keep an eye on this weight because too much snow accumulation has the potential to cause roof collapse, particularly on older or improperly maintained buildings.

New snow typically weighs between five and twenty pounds per cubic foot, or between fifty and two hundred kilograms per cubic meter. The weight of this snow can build up quickly on your roof. For example, an additional 5 to 20 pounds per square foot, or 25 to 100 kilograms per square meter, can be added to a roof by just one foot of fresh snow.

As snow melts and refreezes, increasing its density, the weight of the snow becomes even more significant. Particularly wet snow has a tendency to weigh a lot more than fluffy, dry snow. The weight of wet snow can vary significantly from fresh snow, ranging from 30 to 60 pounds per cubic foot (300 to 600 kilograms per cubic meter).

It’s important to take into account not only the current snow load on your roof but also the design of your roof and its weight-bearing capacity in order to evaluate the risk that snow accumulation poses. The minimum roof load capacity needed for various regions is frequently specified by modern building codes, taking snow weight and other factors into account.

It’s wise to keep an eye on the amount of snow on your roof during the winter. If there is a noticeable buildup of snow, you can safely remove it with basic tools like roof rakes. Maintaining the structural integrity of your home and preventing the accumulation of dangerously heavy loads can be achieved by routinely clearing your roof.

How the roof is calculated?

In order to calculate the parameters of the snow coming from the roof, the computation starts with determining the roof geometry in order to obtain sizes to determine the areas and the angles of the slopes.

The Russian Federation’s territory is zoned according to the weight of the snow cover as determined by calculations.

Now that we know the area of the roof and the weight of each material, we can calculate the weight of the pie, which will result in constant loads on the rafter portion. Since it is not a natural tile, the average weight of one square meter is between 25 and 40 kg/m2. In actuality, it is not as important as covering the roof. Any material’s weight characteristics are provided in the documents that go with it; all you have to do is fold them all, multiply the results by the correction coefficient of 1.1, and you’ll have an approximate idea of the weight you want.

The roof was considered in this way, but it should be borne in mind that despite the exact result, the weight of the roof is usually accepted for 55 kg/m2. This is done because in the case of replacing the roof after many years, part of the material may be different and the rafter part will require alteration and strengthening. To avoid this and a stock is taken. Do not think that in this case, the calculation of the load from the material to the roof is not needed, you can get 45 and 50 kg/m2, but you can also 60 kg/m2, and then the rafters will be too weak part of the entire structure.

Features of snow load

Prior to moving on to this section, you should find the house’s location on a map of Russia’s snowfall and obtain data in the form of x kgf/m2. This represents the weight of one square meter of falling snow. The correction factor will be determined by the slope angles of the slopes:

  • less than 25 degrees – 1;
  • at corners less than 60 degrees 0.7;
  • and with more acute angles (for example, 75 degrees) there will be no snow load, since such a slope provides up to 100% of snow.

After considering this outcome, it is required to consider wind effects, which are taken into account based on wind influence tables based on the location and height of the house. Next, after obtaining the weight of one meter calculation, proceed to the rafter section.

Method for forming snow bags. An illustration of a roof with a 20 to 30 degree slope.

The rafter part of the roof

After determining the load on the m squares, we must compute the rafter portion. Mauerlat is the most crucial component of the rafter system. This beam is fixed to the top edge of the wall and is used to evenly disperse the weight of the roof across the house’s walls. Here, there are some guidelines but no calculation values.

First off, a quarry bar is the best option.

Second, it is installed with a minimum of 3 cm remaining to the bearing wall’s width angles (better than 5). Put another way, the width of the Mauerlat will be 30 cm when the thickness of the faith is 40 cm thicker than the wall.

Regulatory snow load diagram with coefficient M. In SNiP 2.01.07-85, additional values for the coefficient M are provided.

Thirdly, the Mauerlat is installed with a 3-5 cm overlap on thin walls (like those made of monolithic reinforced concrete). For instance, if the wall is 10 cm thick, the width of the Mauerlat will be 20 cm.

This is done in order to prevent damage to the wall’s most vulnerable edges during load distribution. The best way to calculate the rafters is to use online calculators and other programs that can be found on the Internet. The most important thing to remember in this situation is to enter all of the data precisely and carefully. This will ensure that all structural elements are taken into account.

We highlight the fact that not all programs of this type account for the result’s deflection. The ability of the rafters to bend for a specific amount of millimeters under load is known as deflection, and the longer the beam, the larger the deflection. If the software doesn’t have this option, you can locate a beam that is specifically made for you in any materials directory and find out which linear M deflection it has.

The correction coefficient is straightforward: a 20% increase in beam section is required when the deflection exceeds allowable limits (10–15 mm). That is, a 50×200 mm beam that the program determined to be 50×240 mm.

What we get as a result of everything

Following all computations, we are able to determine the weight of the roof, the number of beams, the composition of the structural elements, and the weight of the roof overall while accounting for wind and snow loads. The distribution of weight exposure to the wall still needs to be assessed, compared to the wall’s material strength, to ensure that the wall can support the weight.

It is important to remember that the wall’s margin of safety should be at least 25–30% because, even in peaceful areas, strong winds or a lot of snowfall are common, and the peak load may momentarily exceed the calculation. Generally speaking, these impacts are transient, and the rafter system can tolerate them; however, in the event that the wall lacks a safety margin, as you are aware, the wall may collapse and the Mauerlat bunch will be destroyed.

Thus, pay attention to this matter and make use of this article so that, in the event that you are unable to perform all of the calculations yourself, you can manage the designer’s calculations.

For roof safety in areas with frequent snowfall, knowing the weight of snow per square meter is essential. Various factors, such as moisture content and snow density, can affect how much snow is on your roof. This article explains how to compute snow weight, why it matters for various kinds of roofs, and offers helpful advice on how to manage snow accumulation to keep things safe and structurally sound throughout the winter. Comprehending these fundamentals can aid homeowners and builders in making knowledgeable choices regarding roof construction, upkeep, and safety precautions in regions with heavy snowfall.

Load perceived by rafter structures

Two loading groups of the loads are permanent and temporary (long, short-term, special), depending on how long the loads will last.

  • TO constant loads It is necessary to attribute the load from the weight of the structure itself: roofing, the weight of the rafter structure, the weight of the heat -insulating layer and the weight of the ceiling finishing materials;
  • TO short -term loads include: the weight of people, repair equipment in the roof service and repair area, snow load with full calculation value, wind load;
  • TO special loads. for example, they include seismic effects.

Rafter structure computation The first and second groups of loads’ marginal states indicate that they should be executed with consideration for their unfavorable combination.

Snow load

The formula S = sg*m yields the total calculated value of the snow load, where SG is the calculated weight of the snow cover on the 1 m2 horizontal surface of the roof, as determined by the snowy district of the Russian Federation and taken according to the table. m is the coefficient of transition between the snow cover’s weight and the snow load and coating. Depending on how steeply the roof slopes at an angle,

  • At the angles of the slope of the roof slope less than 25 degrees Mu are taken equal to 1
  • At the angles of the slope of the roof slope from 25 to 60 degrees, the value of MU is taken equal to 0.7
  • At the angles of the slope of the roof of a roof of more than 60 degrees, the value of Mu, in the calculation of the full snow load, is not taken into account

Table for determining the snow load of the terrain

Wind load

Example 1. Calculation of snow load on the rafter system of the roof for Moscow and the Moscow region

Initial data:

  • Region: Moscow
  • Roof slope 35 degrees

Find the full calculated value of snow load S

  • The full calculated value of snow load is determined by the formula:S = sg*m
  • On the map of the snow cover zones of the territory of the Russian Federation, we determine the number of the snow region for Moscow, in our case – this is III, which corresponds to the weight of the snow coating according to the table Sg = 180 (kgf/m2) ;
  • The transition coefficient of the weight of the snow cover to the snow load to the coating for the roof angle of 35 degrees m = 0.7
  • We get: S = sg*m = 180*0.7 = 126 (kgf/m2)

Example 2. The calculation of the wind load on the rafter system of the roof for Moscow and the Moscow region

Initial data:

  • Region: Moscow
  • Roof slope 35 degrees
  • Building height 20 meters
  • Type of terrain – urban territories

Find the full calculation value of the wind load W

  • The calculated value of the average component of the wind load at height Z above the surface of the earth is determined by the formula: W = Wo*K ,
  • On the map of wind pressure zones in the territory of the Russian Federation, we determine for Moscow Region I
  • The normative value of the wind load, which corresponds to the first area, is accepted Wo = 23 (kgf/m2)
  • The coefficient K, taking into account the change in wind pressure in height Z, is determined by the table. 6 k = 0.85
  • We get: W = Wo*K = 23*0.85 = 19.55 (kgf/m2)

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Snow load on the roof: calculation and normative value for SNiP

One of the key technical solutions during roof construction is calculating the maximum snow load, which establishes the rafter system’s structure and the thickness of the supporting structure’s components. The location of the house and the SNiP norms are taken into consideration when determining the normative value of snow load for Russia. The load value needs to be computed when designing the roof in order to lessen the possibility of negative effects from an excessive snow mass weight. The necessity of installing snow retainers to stop snow from converging from the roof overhang is given special consideration.

In addition to the provision of excessive load on the roof, the snow mass, sometimes, is the cause of leaks in the roof. So, when the strip of ice is formed, the free flow of water becomes impossible and the melt snow is more likely to fall into a subcutaneous space. The largest snowfalls are on the share of mountainous areas, where the snow cover reaches several meters in height. But, the most negative consequences from the load occur during periodic thawing, ice and freezing. At the same time, deformations of roofing materials, improper operation of the drainage system and an avalanche -like snow flow from the roof of the house are possible.

Factors of the influence of snow load

It should be considered that up to 5 percent of the snow mass evaporates in a day when estimating the load from snow masses on the pitched roof. He can now crawl while being carried by the wind and covered in nastom. These changes bring about the following unfavorable effects:

  • The load from the snow layer on the bearing structure of the roof has the ability to increase several times with sharp warming with subsequent frost; This causes an excess of the load, the calculation of which was carried out incorrectly; The rafter system, waterproofing and thermal insulation are subjected to deformations;
  • The roof of a complex shape with numerous adjacents, fractures and other architectural features has the ability to collect snow; This contributes to an uneven load, which is not always taken into account when calculating;
  • The snow that slides to the cornice gathers near the edges and provides a danger to a person; For this reason, in areas with a large amount of precipitation, it is recommended to install snow retainers in advance;
  • Snow sliding from the cornice can damage the drainage system; In order to avoid this, you need to clean the roof in a timely manner or use snow retainers.

Ways to clean the roof of snow

Manual cleaning is the proper course of action in this situation. However, doing such work puts a person in grave danger in terms of security. Because of this, the design of the roof, rafter system, and other roof components are greatly influenced by the load calculation. It’s a well-known fact that less snow will accumulate on roofs on colder slopes. The roof’s inclination ranges from 45 to 60 degrees in areas that receive a lot of snowfall during the winter. Simultaneously, the computation reveals that an abundance of complex compounds and adjacents contribute to uneven load.

With cable heating systems, icicles and ice are not allowed to form. Directly in front of the drainage gutter, the heating element is mounted around the roof’s perimeter. Either an automatic control system or manual control of the entire process is employed to regulate the heating system.

Calculation of the mass of snow and load on SNiP

Snowfall can cause the load to deform the roof’s materials, the rafter system, and other components of the house’s supporting structure. The structure is calculated based on the load’s exposure during the design phase to avoid this. Snow typically weighs 100 kg/m 3. Moreover, its mass can reach 300 kg/m 3 when wet. With only the thickness of the snow layer as a guide, it is easy to compute the load on the entire region once these values are known.

The stock coefficient, which is 1.5, is multiplied by the thickness of the cover, which should be measured in the open area. A unique snow load map is used, taking into consideration the regional characteristics of the area in Russia. The SNiP requirements and other regulations are constructed upon it. The following formula is used to determine the total snow load on the roof:

Where S represents a full snowfall;

Scalc.: the approximate weight of snow on the earth’s horizontal surface per square meter;

The coefficient μ is determined by accounting for the roof’s slope.

The weight of snow at 1 meter square, estimated using SNiP, is recognized on a unique map found below, which covers the entirety of Russia.

According to SNiP, the coefficient μ should have the following values:

  • with a roof slope less than 25 °, its value is one;
  • with a slope of 25 ° to 60 °, it has a value of 0.7;
  • If the slope is more than 60 °. The calculated coefficient is not taken into account when calculating the load.

A good example of calculation

Consider the house roof, which has a 30 ° slope and is situated in the Moscow area. In this instance, SNiP specifies the following method for load calculation:

  1. On the map of the Russian regions, we determine that the Moscow region is located in the 3rd climatic area, where the normative value of snow load is 180 kg/m 2 .
  2. By the formula from SNiP, we determine the full load: 180 × 0.7 = 126 kg/m 2 .
  3. Knowing the load from the snow mass, we make the calculation of the rafter system, which is selected based on the maximum loads.

Installation of snow holders

It is not possible to remove snow from the roof’s surface if the computation is done correctly. Additionally, snow retainers are used to prevent it from sliding off the cornice. They don’t require clearing snow off the house’s roof, making them incredibly convenient to use. When the standard snow load is less than 180 kg/m 2, tubular structures are employed in the standard version. Snow detainees are installed in multiple rows using a denser weight. Cases where snow holders are used are specified by SNiP:

  • with a slope of 5% or more with an external drain;
  • Snow holders are installed at a distance of 0.6-1.0 meters from the edge of the roof;
  • During the operation of tubular snow retainers, a continuous crate of the roof should be provided under them.

Additionally, SNiP explains the location of installation, the method of operation, and the fundamental designs and geometric measurements of snow retainers.

Region Snow Weight (kg/m2)
Northern Europe 70-150
Canada 150-400

For both homeowners and builders, knowing the weight of snow per square meter is essential, particularly in areas that frequently experience significant snowfall. The density and moisture content of snow can have a significant impact on its weight. Wet, compacted snow can weigh significantly more, ranging from 30 to 100 kg per square meter or even higher in extreme cases, than light, fluffy snow, which can weigh as little as 3-5 kg per square meter.

A roof collapsing or structural damage occurring from an excessive amount of snow accumulation can be extremely dangerous. The minimum roof load capacity required to withstand normal snow loads in an area is frequently specified by building codes. It is imperative that homeowners follow these guidelines and keep an eye on the amount of snow accumulating on their roofs, particularly during periods of intense precipitation.

The amount of snow that a roof can safely support depends on a number of variables, such as the building’s structural soundness, roofing material type, and roof slope. For example, steeply pitched roofs naturally shed snow more efficiently than flat roofs, which are more prone to snow accumulation.

Homeowners can take preventative measures, like routine snow removal or installing heating systems to melt snow on the roof, to avoid issues related to excessive snow weight. To prevent harming the roof or putting oneself in danger, it is imperative to do the task safely, utilizing the proper instruments and methods.

In conclusion, it is critical for builders and homeowners in snowy regions to comprehend the weight of snow per square meter and how it affects roof safety. Through vigilant monitoring of snow accumulation, staying up to date on local building codes, and implementing appropriate preventive measures, homeowners can contribute to the safety and durability of their roofs throughout the winter season.

Video on the topic

How much snow weighs? | Village sketches

Experiment: We determine the density of snow and the real load on the canopy

How much snow on the roof is collected over the winter. Snow load on KV.m

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Gleb Zuev

Exterior designer, author of books about roofing materials. I will help you make your roof not only reliable, but also beautiful.

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