Specific gravity of pine logs. How much does a cube of pine weigh depending on humidity? In short, the results

When starting to build a house or make renovations, sometimes you have to face questions that seem simple at first glance, but you can’t answer them right away. It seems awkward to approach specialists with such a question, but you need to know for sure. For those who can turn to the Internet, it’s easier - type in a search engine “How much does a cube of wood weigh” and in half a minute received a comprehensive result. By the way, really, how much?

The effect of humidity on the weight of wood

The weight of wood does not always have the same value. What does it depend on? First of all, from the moisture content of the wood. If we compare, for example, oak and birch, it turns out that a cubic meter of oak weighs 700 kg, and a birch weighs 600 kg. But it could be different. Weighing a cubic meter of birch, we get 900 kg, and oak will show the same 700. Or in both cases it will be 700 kg. Why do we get such different numbers? In this case, the moisture content of the wood plays a role.

There are four degrees of humidity: dry (10-18%), air-dry (19-23%), damp (24-45%) and wet (above 45%). Thus, it turns out that different rocks with the same humidity have different weights, as in the first example above. If the humidity is not the same, then the weight may fluctuate in one direction or another. The standard humidity is 12%.

Different density - different weight

Another factor that affects the weight of wood is its density. The highest density is found in iron and ebony wood - from 1100 to 1330 kg/m3. Boxwood and bog oak are close to them - 950-1100. For ordinary oak, beech, acacia, pear, and hornbeam, the density is about 700 kg/m3. It is even lower for pine, alder, and bamboo - 500 kg/m3. And the lowest is for cork wood, only 140 kg/m3.

Why do you need to know the weight of a cubic meter of wood?

Having knowledge in this area is sometimes very important. When purchasing building material, its quantity cannot be determined by eye by a non-specialist. Knowing the dimensions of the timber or lining, the material from which they are made and its moisture content, simple calculations allow you to determine the weight of the purchased product. How much does a cube of wood weigh? In this case, the answer to this question will help you figure out whether the seller sent you the goods correctly.

Heat transfer from wood

In addition, there is another indicator - heat transfer. It will come to the aid of those who use wood as firewood for heating. The higher the hardness, i.e. The density of the wood species, the higher its calorific value. Of course, no one will heat a room with boxwood, but when choosing between linden and pine or birch and acacia, you can get much more heat if you know which of these species is the hardest. Information about the density of each tree can be gleaned from the tables, since all this information is systematized for ease of use.

Weight of a dense cubic meter, kg

The table shows average mass values. Possible maximum and minimum mass values ​​are 1.3 and 0.7, respectively, from its average value

What is the specific gravity of pine? The specific gravity of pine is measured in kg/m3 and is determined by the density of pine wood measured in g/cm3. Unlike many other materials, wood, in particular pine coniferous wood, is characterized not by one specific gravity value, but by a fairly wide range of values. The fact is that pine, like any other tree, is a porous natural material that has natural moisture. In other words, pine wood always contains some amount of water, which significantly affects its density, and therefore the specific gravity of pine. In general, the question of what is the specific gravity of pine has no practical meaning, without specifying the moisture content of the wood sample. And the moisture content of pine wood can fluctuate over a wide range. They distinguish, for example: the specific gravity of pine at natural humidity, the specific gravity of pine in a freshly cut state, the specific gravity of wet, damp, damp, dried, dried, dry and absolutely dry pine wood. The quality of pine wood is reflected in the grade of softwood lumber, for example: 1st grade pine, 2nd grade pine, 3rd grade pine. For each variety of pine, the density and specific gravity of the tree will be different. Although the determining parameter for the specific gravity value still remains the moisture content of the wood. However, with the same wood moisture content, for example 12%, the specific gravity of grade 1, 2 and 3 pine will be different.

The highest specific gravity is for growing, not yet cut down or felled pine. This is due to the maximum moisture content of the tree in the “standing” state. What is the specific gravity of pine in its natural state? The fact is that the natural moisture content of pine wood is not standardized in advance as a reference parameter, but is actually determined. And it strongly depends on the growing conditions of the coniferous tree, as well as the season of harvesting pine wood. It can range from 29 to 81%. Accordingly, the natural specific gravity of pine can vary in the same wide range of values. From a practical point of view, specific gravity at natural humidity is usually of little interest, since it is an initial characteristic and changes quickly. Already in the freshly cut state, the specific gravity of the pine tree decreases from its initial value, the one that was in its natural state “on the root.” With all types of storage and transportation, even without special drying, pine wood loses moisture, dries and the specific gravity of pine decreases. Pine has the lowest, lowest density and lowest specific gravity in an absolutely dry state, precisely because the moisture content of such coniferous wood is very low.

When processing coniferous wood, selling pine lumber, using wood in construction and making pine carpentry. Of practical interest is the specific gravity of wet (moist, damp, dried) and dry pine. At the same time, despite the fact that such tree names as: wet, damp, damp pine wood are widely used by coniferous wood harvesters, trading organizations and woodworkers, carpenters. There is no clear specific connection of such definitions to specific percentage humidity values. Dried pine is freshly sawn pine wood that has been stored for a long time under conditions in which natural drying of the wood occurs “along the way.” Its actual density and specific gravity can also be different and are not standardized by any norms and rules (SNiP, GOST). Dry pine is coniferous wood that has been specially dried. However, for specific products and types of work, the moisture content of dry pine is determined by special requirements for these particular pine wood products and is regulated separately by GOST and SNiP. For example, in the manufacture of wooden products and structures intended for use outdoors, dry pine is considered to be wood with a moisture content of 11–14%. For pine wood products used in residential premises, dry wood is wood with a moisture content of 8 - 10%. And for parquet, dry pine is used with a parquet board moisture content of 6 - 8%. So the specific gravity of dry pine is also indicated in accordance with the technological requirements for wood moisture content, for specific products and types of work. Therefore, it is technically competent and correct from a technological point of view to operate with the values ​​of the specific gravity of pine using non-general terms: wet, wet, damp, dry wood. And indicate the specific gravity of pine only in relation to the moisture content of the tree. As additional information, you need to take into account the grade of coniferous lumber: the specific gravity of pine of 1st grade, 2nd grade and 3rd grade. Specific values ​​of the specific gravity of pine wood for different wood moisture content (kg/m3) and the corresponding density of pine (g/cm3) can be found in Table 1.

Table 1. Pine specific gravity. Specific gravity of pine? Density values ​​at different humidity levels of pine wood. See the answer in table 1. .

The weight of the forest does not always have the same value. What does it depend on? First of all, from the moisture content of the wood. If we compare, for example, oak and birch, it turns out that a cubic meter of oak weighs 700 kg, and a birch weighs 600 kg. But it could be different. Weighing a cubic meter of birch, we get 900 kg, and oak will show the same 700. Or in both cases it will be 700 kg. Why do we get such different numbers? In this case, the moisture content of the wood plays a role.

There are four degrees: dry (10-18%), air-dry (19-23%), wet (24-45%) and wet (above 45%). Thus, it turns out that different rocks with the same humidity have different masses, as in the first example above. If it is not the same, then the weight may fluctuate in one direction or another. The standard humidity is 12%.

How much does a cube of wood weigh? Table.

The weight of a cubic meter of forest products, as stated above, depends on the type of wood and humidity.

The heaviest tree is snakewood (Piratinera Guiana, Brosinum Guiana, “snake tree”, “speckled tree”), its dry weight is 1300 kilograms per cubic meter.

The lightest wood is balsa (balsa, ochrome pyramidal, “cotton tree”), its dry volume is 130 kilograms per cubic meter.

The table below shows data on the weight of a cubic meter (cube) of 170 different types of wood at a standard humidity of 12%.

Having the table described above at hand, you can always easily calculate the required weight of a particular tree.

The board is a certain lumber that is up to 100 mm thick and, usually, twice as wide. It is made from beams or logs of various tree species as a result of longitudinal division of round timber and division of the resulting parts. All this production is carried out on special equipment and machines. This type of material is used in all areas of production or construction work where the use of wood is necessary.

When working with materials such as boards, it is necessary to take into account its quality. A characteristic such as specific gravity will help determine this parameter.

Board Specific Gravity Table

If the density of the material is known, the specific gravity of the board can be easily calculated without the use of specialized equipment. The average values ​​of such parameters as the weight of the board and the weight of 1 m3 of the board can be easily calculated using the table below.

Specific Gravity Calculations

In order to carry out the necessary calculations, it is necessary, first, to determine the value itself. Specific gravity is the ratio of the weight of the substance being sought to its occupied volume. All these calculations occur thanks to the formula: y=p*g, where y is the specific gravity, p is the density, g is the acceleration of gravity, which in normal cases is a constant and equals 9.81 m/s*s.

The result is measured in Newtons divided by cubic meter and denoted N/m3. In order to convert to the SI system, that is, in kg/m3, the resulting value must be multiplied by 0.102.

A parameter called density is the amount of its mass in kilograms that can fit in a cubic meter. A very ambiguous value that depends on many factors. The main factors for boards are humidity and wood type. So, this parameter can vary from 380 to 1330 kg/m3.

1. Tree species groups
2. Humidity dependent
3. Impact on wood quality

Wood density is one of the main characteristics of a cubic meter of material, which is taken into account when calculating structures and choosing raw materials for the production of various products. The concept refers to the ratio of the mass of a material to the measured volume.

What is the forest density?

Different tree species have approximately the same composition, so in dry form the absolute specific gravity for all will be roughly the same. Its average value is 1.54 (dimensionless value). But the wood density table shows its own numbers for different species. The fact is that in a completely dry state it is almost impossible to measure the absolute parameter. To do this, it is necessary to completely get rid of moisture in the test sample and eliminate air voids. In practice, as it turned out, it is difficult to fix the parameter, and it is not suitable for calculations.

To determine the density of lumber, calculating its specific gravity is more suitable.

It is influenced by:

• humidity;
• rock porosity.

The specific gravity of wood has the form of the average value of density calculations in its different states. This figure may vary slightly in sources. The difference is due to changes in the moisture level inside the trunk. To avoid confusion, we present a table with average specific gravity values ​​at each individual moisture level for different wood species in ascending order.

Table of wood densities of different humidity levels (kg/m3)

Tree species groups

Typically, the table value of the density of timber and other lumber is measured at a humidity of 12%. Depending on the obtained value, tree species are divided into 3 groups:

1. With low volumetric mass (less than 540 kg/m3). These include coniferous trees: and some deciduous trees. These are all types, linden, aspen, chestnut.
2. With an average specific gravity of 550–740 kg/m3: elm (elm), larch, all types of maple, rowan, apple, ash.
3. With a high level of density over 750 kg/m3: birch, oak (Araksin, chestnut-leaved), hornbeam, dogwood, pistachio.

Of course, this is an incomplete list of breeds. Based on the wood density values ​​indicated in the table, you can determine whether the species belongs to the group.

Humidity dependent

All lumber contains water. Its quantity mainly determines the density of timber and other raw materials: the more moisture in the product, the higher the weight in the measured volume.

The specific gravity of wood in the table is given in average values, since the amount of moisture in one volume is constantly changing - this is a relative value.

Changes occur due to:

• external weather conditions (rain, fog, snow);
• anthropogenic factor (wetting due to human activity).

Thus, a completely dry board practically never happens. Wood moisture content is always above 0%. This indicator can be determined using a special device - a moisture meter.

Impact on wood quality

The average specific gravity is the main characteristic of raw materials when carrying out calculations, since the value contains an average assessment of tests of lumber in different states of water saturation.

According to the laws of physics, the calculated density is directly related to the strength of the material: the higher the specific gravity of the volume of the product, the greater the load it can withstand. This rule also applies to wood.

Let's look at an example:

• Oak has a high specific gravity and is famous for its reliability and durability. It has almost no empty pores, the entire volume is filled with strong wood fibers and moisture. Load-bearing structures of houses and industrial facilities are made from oak. Wood with a high specific gravity is rigid and practically does not bend.
• Cedar and birch beams have a low volumetric weight, which is why they are not used to create load-bearing elements of the frame of structures. These rocks are more suitable for finishing work, where the load on the product is minimal. Wood with low porosity is plastic and bendable.

Relationship between density and thermal conductivity

This indicator is important for choosing a tree when preparing firewood. The relationship is direct: the higher the density index, the more fuel there is in the lumps, the longer they will burn. Wood species with a high mass-to-volume ratio are called solid fuels. They burn for a long time, give good heat, but due to their dense structure they are difficult to prick. The advantage of firewood and fuel from light tree species is their flexibility in sawing and cutting, but they have a relatively small energy reserve. The logs will burn for a significantly shorter amount of time.