In construction work involving the use of sawn timber from coniferous trees, correct calculations of the specific gravity of pine wood are very important. Unlike other various building materials, this variety does not have a single specific gravity, which somewhat complicates the selection process. The fact is that pine wood, like any wood, is a natural material of a porous type. Accordingly, depending on the variety of pine and on the percentage of moisture, the specific gravity of the pine changes.
As mentioned above, the main parameter affecting the volumetric weight of pine is humidity. So, for example, the highest specific gravity of the still untouched, growing pine. This is due to the fact that the tree needs a lot of moisture for growth. At the same time, moisture is both a useful substance and a carrier of other, no less useful, vitamins and minerals. The amount of moisture depends entirely on the variety of pine, harvesting season and locality. Moisture indicators of "live" pine can vary from 29% to 81%. The lowest indicator, respectively, is in dried pine, since the humidity in this state tends to zero.
Weight table for 1 m3 of pine depending on its moisture content.
It is very difficult to determine the percentage of moisture with improvised means. And this is a very important indicator for determining such a parameter as the specific gravity of a cubic meter of pine. Usually, these procedures take place in special technological laboratories.
The easiest way, when buying a material, is to clarify the composition of the humidity from the manufacturer. Then, using the presented table, find out the weight of a pine cube with a flag from 5% to 90% and the density of the material:
| Pine Moisture Percentage | Specific gravity (kg/m3) | Density (g/cm3) |
| Standard, 10 to 12% | 500 - 505 | 0,5 - 0,505 |
| 1 - 5 % | 480 | 0,48 |
| 12 % | 505 | 0,505 |
| 15 % | 510 | 0,51 |
| 20 % | 520 | 0,52 |
| 25 % | 540 | 0,54 |
| 30 % | 550 | 0,55 |
| 40 % | 590 | 0,59 |
| 50 % | 640 | 0,64 |
| 60 % | 680 | 0,68 |
| 70 % | 720 | 0,72 |
| 78 - 90 % | 750 - 820 | 0,75 - 0,82 |
| 80 % | 760 | 0,76 |
| 100 % | 850 | 0,85 |
Practical value and importance.
Among coniferous building materials, wet, dried, dry and damp pines are valued. However, these terms do not give a definite exact meaning of humidity, so it is extremely important to know clear numbers. So, for example, the requirements for the use of fallen pine are not provided for by legislative acts. But, when performing certain work, GOST establishes humidity standards, for example:
The Drova72 company conducted an experiment, we weighed 1 stacking cube (skladometer) of birch split firewood, natural humidity, ~ 50%. The results of this experiment will be discussed in more detail below.
This experiment in no way claims to be - "scientific" or "100% objective", rather something in between information from the Internet and laboratory research. Nevertheless, this is the first step towards truth and objectivity.
Next time we will repeat the experiment and try to find a moisture meter, as well as film the whole process on video.
In short, the results
At humidity ~50% and log length ~50cm:
- 1 folding cube weighs ~561 kg;
- 1 dense cubic cube weighs ~790 kg.
In the text below, we reveal in detail the essence of the experiment. The calculation is made on the basis of information from GOST "a 3243-88 and a guide to sawmilling.
Why do we need this?
small digression
The volume of firewood in stock meters is measured by multiplying the length, width and height of the woodpile. But, the concept of "1 storage cube of firewood" is rather vague, because. firewood in the woodpile can be stacked with different stacking densities and there is no GOST or regulation that would explain what "packing density" is and how to measure it. That is, the same amount of firewood (1 conditional storage meter) can fit from ~0.7 to ~1.3 stock meters, depending on the stacking density and the condition of the logs (their curvature, the presence of knots).
For clarity, look at the photo below. It is obvious that the firewood on the right is stacked thoroughly and the number of poles in such a woodpile is greater than in the one on the left. In this case, in both cases, the volume of firewood in the warehouse meters will be the same, but the mass is different. Those. in fact, the amount of firewood in the photo on the left is less. 
In the photo above, please do not pay attention to the different types of firewood, this image shows the density of stacking firewood in a woodpile.
specifics
Sometimes we have disagreements with our clients about the volume of firewood in the warehouse meters. We brought firewood to stacking in one volume, the client transferred the firewood to his woodpile, measured it, and his volume turned out to be less than originally declared.
In the example above, the contention is almost always due to stacking density. Therefore we decided weigh 1 stack of birch firewood, and correlate its weight (mass) with the data, which are presented in GOST 3243-88 and in the Sawmill Handbook, Moscow, Forest Industry Publishing House, 1980
By comparing the weight of our firewood storage meter with the data from the above sources, we will understand whether we stack the firewood tightly enough in the car before delivering it to the buyer.
Sequencing:
- First, we will put 1 stacking cube in the woodpile.
- Weigh this cube on the scales.
- We will compare the resulting weight with the data from GOST 3243-88 and the Sawmill Handbook.
According to various sources, the moisture content of freshly sawn birch can vary from 60 to 80%. We buy firewood birch, which is harvested (cut down) from 1 to 4 months ago from the moment when it is brought to us for further processing. The humidity of such a birch is on average 40-50%. We will do the calculation based on 50% humidity.
In the guide to sawmilling, the weight of a dense cube of ordinary birch at a moisture content of 50% is 790 kg. To convert the weight of the warehouse meter to a dense cube (or vice versa), you need to apply a coefficient. We will take it from GOST 3243-88, with a log length of up to 0.5 meters of split hardwood - coefficient is 0.71.
790 * 0.71 = 560.9 kg
Those. the mass of our split birch firewood storage meter must be at least 561kg.
We weigh
Conclusions and comments
First of all, we wanted to test ourselves, because. sometimes there were doubts about honesty in relation to our firewood buyers. Now the doubts have been dispelled. Our stacking density and volume of firewood in stacked cubic meters meets the necessary requirements.
If we turn again to the guide to sawmilling (Note 1), it is obvious that the weight of 1 storage cube at a moisture content of 50% will not always be 560.9 kg, because. the weight of one dense cube of 790 kg is an average value and can range from 553 kg to 1027 kg. And, therefore, 1 birch chipped firewood storage meter (taking into account the coefficient 0.71) can weigh from 392kg to 729kg. This is probably due to the different density of trees and poles.
Of course, this experiment cannot be considered 100% objective, because. At a minimum, a moisture meter is needed to determine humidity. Our forest can have different humidity levels. There are many suppliers and the terms of harvesting and delivery are different for everyone, respectively, the moisture content of the forest can vary from 30 to 60%.
If you have any suggestions or comments on this material - please write to our email: mail@site.
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Wood has been used in construction work since ancient times. Of course, because this material is still very popular due to the presence of excellent technical characteristics. Wood, in itself, is a natural material of a structured type, consisting of wood cells and pericellular voids, which in turn does not at all guarantee that one part of the wood will be equal to another of identical size. Therefore, so often, in the process of work, the question arises of calculating the required amount of this material and such parameters as: the weight of the wood as a whole and the weight of the cube of wood.
| wood species | Humidity percentage, % | ||||||||||
| Fresh | 100 | 80 | 70 | 60 | 50 | 40 | 30 | 25 | 20 | 15 | |
| Larch | 940 | 1100 | 990 | 930 | 880 | 820 | 770 | 710 | 700 | 690 | 670 |
| Poplar | 700 | 760 | 690 | 650 | 610 | 570 | 540 | 500 | 480 | 470 | 460 |
| Beech | 960 | 1110 | 1000 | 950 | 890 | 830 | 780 | 720 | 710 | 690 | 680 |
| Elm | 940 | 1100 | 1100 | 930 | 880 | 820 | 770 | 710 | 690 | 680 | 660 |
| Oak | 990 | 1160 | 1160 | 990 | 930 | 870 | 820 | 760 | 740 | 720 | 700 |
| Hornbeam | 1060 | 1330 | 1330 | 1130 | 1000 | 990 | 930 | 860 | 840 | 830 | 810 |
| Norway spruce | 740 | 750 | 750 | 640 | 600 | 560 | 520 | 490 | 470 | 460 | 450 |
| walnut | 910 | 1000 | 1000 | 850 | 800 | 750 | 700 | 650 | 630 | 610 | 600 |
| Linden | 760 | 830 | 830 | 710 | 660 | 620 | 580 | 540 | 540 | 530 | 500 |
| White acacia | 1030 | 1330 | 1330 | 1190 | 1060 | 990 | 930 | 860 | 840 | 830 | 810 |
| Alder | 810 | 880 | 880 | 750 | 700 | 660 | 620 | 570 | 560 | 540 | 530 |
| Maple | 870 | 1160 | 1160 | 990 | 930 | 870 | 820 | 760 | 740 | 720 | 700 |
| common ash | 960 | 1150 | 1150 | 930 | 920 | 860 | 800 | 740 | 730 | 710 | 690 |
| Siberian fir | 680 | 630 | 630 | 540 | 510 | 470 | 440 | 410 | 400 | 390 | 380 |
| Scotch pine | 820 | 850 | 850 | 720 | 680 | 640 | 590 | 550 | 540 | 520 | 510 |
| Caucasian fir | 720 | 730 | 730 | 620 | 580 | 550 | 510 | 480 | 460 | 450 | 440 |
| Cedar pine | 760 | 730 | 730 | 620 | 580 | 550 | 510 | 480 | 460 | 450 | 440 |
| Birch | 870 | 1050 | 1050 | 890 | 840 | 790 | 730 | 680 | 670 | 650 | 640 |
| Aspen | 760 | 830 | 830 | 710 | 660 | 620 | 580 | 540 | 530 | 510 | 500 |
Depending on the type of construction work, it is necessary to measure wood in different ways. The density of the material is of particular importance to the weight of m3 of wood, therefore, in order to correctly resolve the issues raised, it is necessary to determine the value of the density. There are two types of density:
Specific gravity (density of the wood substance)
Volumetric weight (density of a structured physical body)
Wood substance is a mass of solid wood materials without natural voids. This type of density is measured in laboratory conditions, as it requires additional measurements that are impossible under normal conditions. For each wood of all types and species of trees, this value is a constant and is 1540 kg/m3.
The density of the wood itself is quite easy to determine under normal conditions. To do this, just weigh a piece of wood and measure its volume. Process the obtained data with standard arithmetic operations according to the following formula: Y \u003d M / O, where Y is the specific weight of the tree, M is the mass of wood, O is the volume occupied.
Table of volumetric weight of 1m3 of wood depending on humidity.
The density of the wood substance, as already mentioned, is a constant. However, wood has a multicellular fibrous structure of a complex type. The walls of the wood substance play the role of a frame in the wood structure. Accordingly, for each breed and species of trees, the cell structures, shapes and sizes of cells vary, as a result of which the specific gravity of the tree will be different, as well as the different weight m3 of the tree.
Also, humidity plays an important role in changing the specific gravity of wood. Due to the structure of this material, with an increase in humidity, the density of wood also increases. However, this rule does not apply to the density of the wood substance.
Below is the specific gravity of wood. The table is compiled depending on the moisture content of the material and is calculated such an indicator as the weight of 1 m3 of wood.
Any building materials made of wood, whether it is a terraced or ordinary board, timber, lining or lath, are made from wood of natural moisture. However, in accordance with building codes and GOSTs, any wooden elements, for example, a floorboard of natural moisture, must be dried. The weight of 1 m³ of material depends on this indicator of wood. Although the price is charged per cube, weight matters during transportation. In the article we will figure out how much a wet edged floorboard weighs from the most popular types of wood (oak, birch, pine, spruce, etc.).
The concept of material moisture
Before you know how much a cut, grooved or planed wet and dry floorboard weighs, it is worth clarifying the basic terms and concepts. For the production of terraced, tongue-and-groove, edged or planed boards, different tree species are used. Each breed is a natural material with a structure peculiar only to it. At the same time, one of the characteristics of different rocks is hygroscopicity - the ability of a material to absorb water from the air.
Any wood product (beam, lining, decking or edged floorboards, etc.) will absorb water from the surrounding air in the form of steam. The process of ingress and assimilation of moisture in the material depends on the characteristics of the cell membranes of the rock. Depending on the porosity and rock, the maximum percentage of absolute moisture can be 30.
In addition to hygroscopicity, wood has water absorption - the ability to absorb liquid water when the product comes into direct contact with it. For example, timber, decking or planed boards, lining, tongue-and-groove oak floorboards can absorb water during precipitation, during snowmelt, when the room is flooded, etc. The liquid penetrates through the pores of the material. However, when the level of humidity in the surrounding space decreases, terraced or planed floorboards, timber and other building materials give up their water to the air. Desorption occurs, that is, the material dries.
It is important to know: timber and logs most often give off water through the ends of the product.
The process of absorption and release of moisture by a tree is commonly called the "breathing" of the material. The state of equilibrium between the surrounding space and the internal environment of the element is called equilibrium humidity.
It is also worth knowing that a tree, due to its structure, has different properties depending on the location of the fibers. It is this quality that contributes to the fact that water passes faster along the fibers, and not across. Therefore, timber, edged and planed boards quickly release moisture through the ends of the element.
In addition, sawn timber is characterized by such concepts as relative and absolute humidity. So, absolute humidity is the percentage of the mass of water in the material to the mass of ordinary dry wood. And relative humidity is the percentage of the mass of liquid in wood to the mass of the wet element. This indicator will always be less than the first.
Hygroscopic intracellular water accumulates in the cell walls of the tree, making it more difficult to remove. That is why hygroscopic moisture has a stronger effect on the weight of the cube, the geometry and characteristics of timber, terraced, edged, tongue-and-groove or planed floorboards, lining, slats and other building materials made of wood.
The weight of the cube of elements is also affected by the free unbound moisture in the material. It accumulates in cell cavities and intercellular spaces. This water evaporates more easily and quickly and does not significantly affect the characteristics of the lumber.
Important: when working with wood products, you need to understand and understand the features of the processes occurring inside and related to moisture. After all, this can significantly affect the quality and practical indicators of building materials.
To understand how much a wet oak, alder, spruce or other floorboard weighs, you need to understand the concept of natural moisture - this is the moisture that wood has in a freshly sawn state without the use of drying. Usually this indicator is not standardized. It can be in the range of 30-80%. The weight of a cube of wet wood depends on the growing conditions of the tree and the time of year when the split was made. Winter trees have less moisture than those cut down in summer.
The dependence of the weight of the board on moisture
Convection kiln for wood drying
The price for timber, lining, edged, planed, tongue-and-groove or terraced board depends not only on the weight of the cube, but also on the moisture content of the material. There is a certain division of boards according to the degree of moisture saturation:
- raw board - more than 23% (its price is minimal from $ 30 / m³);
- semi-dry products - 18-23%;
- air-dry edged floorboard - 12-18% (price in the range of 40-50 $ / m³);
- dry terraced, planed or tongue-and-groove boards and timber - 6-12% (the highest price is from 60 $ / m³).
As you can see, the moisture content of the material can be different. For example, the weight of an oak wet floorboard would be 0.99 t/cu. When drying oak lumber to 10%, the weight will decrease to 0.67 t / cu. At the same time, the price for dried wood will increase.
Such an increase in price is due to the fact that many characteristics of the product depend on the degree of saturation of the tree with moisture:
- dimensions;
- decay resistance;
- ease and speed of processing;
- flexibility;
- strength;
- strength of adhesive fixation;
- durability.
Important to know: Wet wood is highly susceptible to rot, mold and other pests. Dry wood is considered ideal, in which the moisture saturation index is brought to the equilibrium at which the processes of swelling and shrinkage practically stop. Therefore, the price of such well-dried lumber is the highest.
How much does a cube of boards from different breeds weigh?
To understand how much an oak, pine, alder floorboard or a board made from other most popular wood species weighs, you can use the indicators below:
- wet pine elements weigh 0.82 t / m³, dry pine floorboards - 0.47 t / m3;
- a cube of oak boards weighs 0.99 tons, and dried products - 0.67 tons / cube;
- wet spruce floorboards weigh 0.76 tons per cubic meter, and dry boards weigh 0.42 tons per cubic meter;
- wet larch weighs 0.94 t / m³, and dry - 0.63 t / m³;
- birch wet building materials weigh 0.87 t / m³, and dried - 0.6 t / m³;
- wet aspen elements - 0.76 t/cube, dry - 0.47 t/cube;
- alder floorboards of natural saturation with moisture weigh 0.81 t/cube, and dried floorboards weigh 0.49 t/m³.
In life, there are situations when you are faced with seemingly simple questions, but you cannot give exact answers to them. During construction, for example, you may need to answer the question: how much does a cube of pine weigh? No one can give an exact answer right off the bat. The weight of timber primarily depends on its species. The second important factor is humidity. Its density depends on the type of wood, which, in turn, directly affects the weight.
In order to know the necessary information if necessary, let's figure out how much a pine cube weighs. This may be necessary when purchasing timber to ensure that the goods are shipped correctly.
Humidity indicators are divided into four degrees:
- wet (more than 45%);
- crude (from 25 to 44%);
- air-dry (from 19 to 24%);
- dry (from 10 to 18%).
So, a cube of pine is how much? The results obtained are presented in the form of a table.
Wood moisture | (from 1 to 5%) | Standard (10 to 12%) | ||||||||||
Weight depending on the type of raw material
There are several types of pine:
- cedar;
- Siberian;
- ordinary.
The weight of wood also varies from its varieties. If the values for the cedar and Siberian are the same, then the weight of the ordinary differs from them. The figures indicated in the table above are typical for ordinary pine.
The weight of one cubic meter of cedar and Siberian is presented in the table below:
So, knowing the moisture content of wood, using tables, it is easy to determine its weight. This is the easiest way. Such tables are often used in construction, where wood is the main material. They help to choose the best type of wood for the construction of a structure.
To begin with, it is worth accepting the fact that softwood is considered to be lighter than hardwood lumber. In addition, such options are easy to process and have a long service life. They are resistant to decay due to the large amount of resins, and therefore are often used as a facing material for building facades.
Before calculating the weight of lumber, it is worth considering the basic concepts:
- Dry wood is a material whose moisture content does not exceed 18%. Such products have already passed the technological stage or have been stored in a warehouse or other dry room for a long time.
- Air-dry lumber is wood with a moisture content of 19 to 23%. It differs in that it has an equilibrium moisture content. This definition should be understood as the state of a tree when its moisture content is in equilibrium with the same parameter of the ambient air. This characteristic is achieved with long-term storage of products in natural conditions. Lumber with this level of moisture excludes the use of technological drying.
- Raw wood - has a moisture content of up to 45%. This forest is still in the drying stage.
- Fresh wood - as a rule, such materials are characterized by a moisture content of over 45%. These are recently felled trees or those that have been under the influence of water for a long time.
It should be understood that determining the specific gravity of the forest is not so simple. At the same time, it can be said which breed will be relatively lighter and which will be heavier. So, coniferous varieties will be guaranteed to be lighter than hardwoods, such as oak or beech. But when transporting a significant amount of timber, all sorts of incidents can happen. As a rule, all these nuances relate to the almost unpredictable weight of raw wood due to high humidity. Therefore, this issue should be dealt with.
Weight of 1 cube of coniferous forest in practice and according to GOST
Depending on the type of wood, 1 m3 of lumber may have a different weight. So, for conifers, especially if they are raw, weight gain due to resins is typical. The moisture content of the forest itself largely depends on the season when the felling was carried out. The conditions for the development of the tree also play a role.
It should be understood that there is lumber from the upper and lower parts of the tree trunk. It is not difficult to guess that the first option will be somewhat easier due to the fact that they initially have high humidity.
Note! Humidity plays the main role in the characteristics of the forest. Raw and dried lumber can have a different weight. Sometimes the differences can be almost twofold.
It is worth considering the provisions of the regulatory literature. So, the current GOST takes the mark of 12% as a standard value for humidity. Under these conditions, light species rarely leave the mark of 600 kg per cubic meter of timber. The lightest among conifers is Siberian fir. The weight per unit volume of such a breed barely reaches 390 kg. But larch, which is also classified as medium, has a weight of 660 kg. Thus, it is heavier than birch, but slightly lighter than oak.
However, calculation tables cannot always give a 100% guarantee that a particular timber at a certain volume will weigh as indicated.
Results
In addition, for the convenience of carrying out calculations, you can use special programs. One of these is the cubic forest. It will allow you to find out without tables how much this or that breed weighs, based on its main parameters. Using the software, there is no need to search for the necessary positions in the table for a long time, it is possible to interpolate. Everything is quite simple. Similar programs show the weight of the forest in kilograms per cubic meter.
Quick answer: mass depends on humidity.
In spring, the demand for wood rises sharply, since spring is the time for active construction. Future buyers are often interested in the question of how much the wood they are going to purchase weighs. Pine is probably the most sought after. It is about this tree that we will talk.
The weight of lumber will depend primarily on its moisture content. Accordingly, the higher the humidity, the more the pine cube will weigh. We have prepared for you the average mass of lumber (pine in our case) per 1 cubic meter, depending on its moisture level.
- Humidity 12% - ~500 kg
- Humidity 20% - ~520 kg
- Humidity 30% - ~535 kg
- Humidity 50% - ~570 kg
- Humidity 70% - ~680 kg
- Humidity 90% - ~740 kg
- Humidity 100% - ~780-820 kg
Please note that the figures are approximate and depend, among other things, on the type of pine, but you understand the general concept of the mass of lumber.
As for natural moisture, this is such an indicator of importance that a tree has immediately after being cut, and for pine this figure is 80-90% (depending on several parameters). Dry wood is considered to be wood, the moisture content of which is 10-15%. Humidity of absolutely dry wood is about 5%.
The edged board differs from the unedged one in that it has the shape of a regular rectangle in cross section. This allows you to stack it evenly, pack it in even bundles, and quite
accurately determine the cubature, that is, the volume of packed materials. If you want to determine the weight of the package, or one cubic meter, it is enough to multiply the volume by the density, which is a reference value and depends both on the type of wood and on its moisture content, that is, the degree of drying.
For the most commonly used wood, you can make a table showing how much a cube of edged board weighs:
lumber type
Weight of one cubic meter, kg
raw pine
890
dry pine
470
raw spruce
790
dry spruce
450
As can be seen from the table, humidity affects how much a cube of edged boards weighs very significantly. Such a large dependence is due to the fact that it is present in large quantities in the cellular structure, and if it is not properly dried, its rapid evaporation can lead to significant distortions in the geometric shape of the boards, bending them.
As a result, it can be argued that the weight of a cubic meter of an edged board can really be determined by the type of wood, referring it to one of the categories.
Light woods include pine, fir and other conifers, as well as poplar. Their average density, that is, the weight of a cubic meter, fluctuates around a figure of 500 kilograms.
Medium breeds - a cubic meter of ash, beech, birch weighs about 650 kilograms.
Heavy breeds, such as oak or hornbeam, have a density of more than 750 kilograms per cubic meter.
How much does one edged board weigh.
How much does one edged board weigh. The most frequently asked question on search engine queries is how much one cube weighs, as a result, one edged board. I continue the series of articles on edged lumber.
At the insistence of colleagues and regular visitors to the site, I continue the series of articles dedicated to lumber. This article is a continuation of the article "How much does one bar weigh." We are talking only about pine, growing in the territory in the Middle Part of Russia. I’ll make a reservation right away that the pine growing in Siberia has a denser texture, and weighs more and costs an order of magnitude more expensive. You can even distinguish it visually, but this is the topic of the next article.
The weight of one cubic meter of freshly sawn and processed into edged pine lumber is about 860 kg.
I will give the calculations in the form of a table for 8486 and recall the calculation formulas.
BOARD SECTION IN MM. QUANTITY, PCS. In 1m3 MATHEMATICAL ACTION WEIGHT OF ONE BOARD IN KG.
Tiu.ru logo300х50х6000
11.1 860kg.: 11.1pcs. 77.5
Tiu.ru logo250х50х6000
13.3 860kg.: 13.3pcs. 64.7
Tiu.ru logo200х50х6000
16.6 860kg.: 16.6pcs. 51.8
Tiu.ru logo150х50х6000
22.2 860kg.: 22.2pcs. 38.7
Tiu.ru logo100x50x6000
33.3 860kg.: 33.3pcs. 25.8
Tiu.ru logo200х40х6000
20.8 860kg.: 20.8pcs. 41.4
Tiu.ru logo150x40x6000
27.7 860kg.: 27.7pcs. 31.04
Tiu.ru logo100x40x6000
41.6 860kg.: 41.6pcs. 20.7
Tiu.ru logo150x30x6000
37.0 860kg.: 37.0pcs. 23.2
Tiu.ru logo200x25x6000
33.3 860kg.: 33.3pcs. 25.8
Tiu.ru logo150x25x6000
44.4 860kg.: 44.4pcs. 19.3
Tiu.ru logo100x25x6000
66.6 860kg.: 66.6pcs. 12.9
To determine on your own how much a cut board with a length of 4000mm and 3000mm, or another, will weigh. I will give an example of a calculation formula in which the necessary condition for the calculation is the number of pieces in 1m3.
For a board, let's say 150x25x3000mm:
1: 0.15: 0.025: 3 = 88.8 pcs. in 1m3
860kg. : 88.8 pcs. = 10 kg.
The weight of this board with a section of 150x25 is 3000mm long. 10 kg.
For a board 150x50x4000mm:
1: 0.15: 0.05: 4 = 33.3 pcs. in 1m3
860kg. : 33.3 pcs. = 25.8 kg.
The weight of one board with a section of 150x50 is 4000 mm long. 26 kg.
At the end of the article, I would like to specifically note that these calculations in Moscow in the markets are the subject of large and small fraud, therefore, each time you need to personally check the “CLASSED LUMBER DIMENSIONS”. Like this! (see photo)
The above calculations in the tables are valid only for lumber of clear "DECLARED DIMENSIONS" with the correct geometry, i.e. corresponding to GOST 8486-86.
For the “Air or Armenian Version” of timber and board, which is sold cheaply at any special sales. prices need a separate approach, because the number of pcs. in 1m3 each time you need to calculate separately in accordance with the actual dimensions that the timber and the board have.
Specific and volumetric weight of wood
Distinguish between the specific gravity of wood (solid wood pulp without voids) and the specific gravity of wood as a physical body. The specific gravity of the wood substance is higher than unity and depends little on the type of wood; on average, it is taken equal to 1.54. The specific gravity of the wood substance is important in determining the porosity of wood.
Instead of the concept of the specific gravity of wood as a physical body, i.e., the ratio of its weight, taken in the same volume at 4 °, in practice the volumetric weight of wood is used. Volumetric weight (weight per unit volume of wood) is measured in g/cm3 and is reduced to normal wood moisture content - 15%.
In addition to volumetric weight, sometimes they also use the reduced volumetric weight, or conditional volumetric weight. Conditional bulk weight is the ratio of the weight of a sample in a completely dry state to the volume of the same sample in a freshly chopped state. The value of the conditional volumetric weight is very close to the value of the volumetric weight in a completely dry state. The ratio between the conditional bulk density (γcond) and the bulk density in an absolutely dry state (γ0) is expressed by the formula
γ0 = γcond/(1-Υ)
where Υ is the total volumetric shrinkage in percent,
γ0 is the volumetric weight of absolutely dry wood.
Volumetric weight of wood.
The conditional bulk weight has the advantage over the bulk weight that it does not depend on the amount of shrinkage and does not require conversion to 15% moisture content. This greatly simplifies the calculations and provides more uniform results when determining γcond for several samples.
The volumetric weight of wood depends on humidity, on the width of the annual layer, on what position the sample occupied in terms of trunk height and diameter. As the moisture content increases, the bulk density increases.
The change in the volumetric weight of wood when dried to a moisture content corresponding to the saturation point of the fibers (23-30%) is proportional to the moisture content; after that, the volumetric weight begins to decrease more slowly, as the volume of wood also decreases. With an increase in the moisture content of wood, the opposite phenomenon is observed.
The numerical relationship between the volumetric weight of wood and moisture content is determined by the following formula:
γw = γ0 (100+W)/(100+(Y0 - Yw))
where γw is the sought volumetric weight at moisture content W, γ0 is the volumetric weight in an absolutely dry state, W is the moisture content of the wood in percent,
Y0 - total volumetric shrinkage in percent when dried to absolutely dry state and
Yw - volumetric shrinkage in percent when drying wood to W% moisture content.
The volumetric weight of wood at a given moisture content can be easily determined with sufficient accuracy from the nomogram proposed by N. S. Selyugin (Fig. 11). Suppose we want to determine the weight of 1 m3 of pine wood at 80% moisture. According to the table 41a we find the volumetric weight of pine wood at 15% moisture, equal to 0.52. On the dotted horizontal line we find the point of volumetric weight of 0.52 and from this point we go along the corresponding inclined line of the reduced volumetric weight until it intersects with the horizontal line showing the moisture content of 80%. From the intersection point, we lower the perpendicular to the horizontal axis, which will show the desired volumetric weight, in this case 0.84. In table. 5 gives the values of the weight of wood of some species depending on the humidity. furniture restoration
Specific and volumetric weight of wood table Figure13
Rice. 11. Nomogram for determining the volumetric weight of wood at different humidity.
The volumetric weight of wood also depends on the width of the annual layer. In hardwoods, the volumetric weight decreases with a decrease in the width of the annual rings. The greater the average width of the growth ring, the greater the volumetric weight of the same breed. This dependence is quite noticeable in ring porous rocks and somewhat less noticeable in scattered porous ones. In conifers, an inverse relationship is usually observed: the volumetric weight increases with a decrease in the width of annual rings, although there are exceptions to this rule.
The volumetric weight of wood decreases from the base of the trunk to the top. In middle-aged pines, this drop reaches 21% (at a height of 12 m), in old pines it reaches 27% (at a height of 18 m).
In birch, the decrease in volumetric weight along the height of the trunk reaches 15% (at the age of 60-70 years, at a height of 12 m).
There are no patterns in the change in the volumetric weight of wood along the diameter of the trunk: in some species, the volumetric weight slightly decreases in the direction from the center to the periphery, in others it slightly increases.
A large difference is observed in the volumetric weight of early and late wood. Thus, the ratio of the volumetric weight of early wood to the weight of late wood in Oregon pine is 1:3, in pine 1:2.4, in larch 1:3. Therefore, in conifers, the volumetric weight increases with an increase in the content of latewood.
Porosity of wood. Under the porosity of wood understand the volume of pores as a percentage of the total volume of absolutely dry wood. The porosity depends on the volumetric weight of the wood: the greater the volumetric weight, the lower the porosity.
For an approximate determination of porosity, you can use the following formula:
C \u003d 100 (1-0.65γ0)%
where C is the porosity of wood in %, γ0 is the volumetric weight of absolutely dry wood.
Table 5 - Approximate weight of 1 m3 of wood of different species in kg
Threshold of the tree Moisture status of the wood
12-18% 18-23% 23-45% fresh cut
Acacia, beech, hornbeam, oak, ash 700 750 800 1000
Birch, elm, elm, chestnut, larch 600 650 700 900
Willow, alder, aspen, pine 500 550 600 800
Spruce, cedar, linden, fir, poplar 450 500 550 800
Softwood lumber is on average considered lighter than hardwood lumber. They are distinguished by ease of processing and durability - resistance to decay, and therefore are often used for carved facade decoration. In addition, it is from coniferous species that the longest sawn timber (more than 6 meters) is produced. Not surprisingly, they are traditionally in high demand.
The weight of lumber depends on the type of wood and humidity.
However, determining their weight is not such a simple matter. Although the main softwoods - pine and spruce - are notoriously lighter than oak or beech, in fact, if the task is to transport a significant amount of lumber by road, you may be in for a catch. “Fresh” wood can often have an unpredictable weight: lumber, depending on the stage of processing, as well as on the forest area where the trees were grown, can vary greatly in properties. Here you need to understand specifically.
The weight of softwood lumber according to GOST and in practice
First of all, humidity plays a decisive role in the properties of wood. Raw wood and dried wood can vary in density by half. This is especially true for conifers.
Raw forest - spruce or pine - gives additional mass to the resin. Humidity depends on the cutting season, on growing conditions, on the part of the trunk from which lumber is made.
In particular, with regard to pine, a tree harvested after the middle of winter (January) will be 10-20% lighter than an autumn one. If the forest area is located in an area with high groundwater (closer than 1.5 m to the surface), the tree will be “overloaded” with water, especially the lower part of the trunk. On the other hand, the “sucked” forest - the one from which the resin was previously collected - will be more than 1.5 times lighter than the untouched one. Needless to say, the weight of 1 m3 of freshly cut wood will also depend heavily on the humidity of the climate and similar circumstances.
In processed form, lumber is more or less equal in weight, but still, those made from the lower part of the trunk are more likely to be heavier: they are initially more moist and retain more water with the same drying. In addition, according to statistics, the beam turns out to be lighter than boards equal to it in cubic capacity (especially unedged ones), even made from the same log: the core of the trunk from which the beam is cut is naturally looser, boards are made not only from the core.
In a word, the mass of raw softwood lumber differs greatly from the mass of dry lumber. On average, the weight of one cubic meter of dry pine is 470 kg, and that of raw pine is 890 kg: the difference is almost 2 times. The weight of 1 m3 of dry spruce is 420 kg, and the weight of 1 m3 of raw spruce is 790 kg.
According to GOST, the standard moisture content for wood is 12%. Under such conditions, spruce has a density of 450 kg / m3, pine - 520 kg / m3, they belong to light species. Among conifers, Siberian fir is even lighter: 390 kg/m3. Nevertheless, there are also heavier species of conifers: larch belongs to the medium-density varieties of wood, the weight of 1 m3 is 660 kg, it surpasses birch and is almost as good as oak.
Nevertheless, if the task is to transport softwood lumber, then the issue of preliminary weighing should be approached as responsibly as possible: random fluctuations in the density of wood may well lead the weight beyond the limits, which is fraught with large fines.
