Timber and firewood of natural humidity are in great demand due to affordable price. **In the article, consider how to calculate their weight, and what you need to take into account.**

## How weight depends on humidity?

**Humidity **– this is the ratio of the mass of water in the wood, to the mass of wood. This percentage is always greater than zero, as water is an integral part of the tree, it is contained in it in a certain amount. The more moisture in the wood, the more she weighs. There are also important characteristics such as density (specific weight) and volume.

**The greatest weight and volume of the tree of natural humidity. This concept can be described in two ways.**

- In a narrow sense – the humidity of freshly dredged forest from 40 to 110%. It is also called the initial. It depends on the tree of wood, the conditions of growth and the season, when it cut down. Different sections of wood have different initial humidity – due to this log from the comlek part will be harder than from the top. Swamp moisture kernel. As the water content is drying in different parts of the barrel (and materials of them), it is leveled to the same (equilibrium) state. On average, the tree of initial humidity weighs 2-3 times more than the dry.
- In a broad sense, it is a tree and lumber above the fiber saturation point, that is, such when the balance of moisture with street air is achieved, and water from wood ceases to evaporate. This indicator is different for different breeds and is caused by the temperature and humidity of the environment, the level of atmospheric pressure. For convenience, use the standard indicator specified in GUT – 22%. That is, in domestic practice, all materials with water content above this level are considered to belong to the materials of natural humidity. Wood 22% humidity weighs 1.5-2 times less compared to initial weight.

The main reason why the material of natural humidity (23-80%) is in demand for purchase – its low cost (20-50% lower than dry). Without pre-drying, it is rarely applied (mainly to create rafter systems, formwork, doomles, flooring), as it gives shrinkage and prone deformation.

Therefore, after purchasing crude, the material is dried to the desired level – in accordance with GOST, humidity must be no more than 14-23% for external work, for internal works – 8-10%.

**For drying, two ways are used.**

**Atmospheric**– allows you to get wood with moisture content at level 18-22% (transport humidity), takes from several months to a year, does not require special equipment. The weight of the material during the natural drying decreases by 25-35% compared with the initial.**Chamber**– Drying is made in the thermal chamber (convective, vacuum, microwave) and takes a few days, allowing you to achieve a humidity of 8-12% (indoor-dry).

The smallest weight compared to the initial, the bedroom-dry wood, dried by an artificial way – its mass is 30-50% less than with initial humidity. When buying building materials, it is important to take into account that when drying is changing not only their weight, but also sizes. And the destruction is uneven in different directions – the width of the wood dries more than in length (the dewin in width is sometimes up to 12%). This is due to the fact that the moisture evaporates not the entire surface of the tree, but flows through the fibers – that is, evaporates mainly through the end surfaces of the log or boards.

The shrinkage coefficients depend on the method of drying and the tree breed (they are listed in reference books). For example, a cutting board of natural humidity with a standard cross section of 150×50 mm (according to GOST 8486) after drying and grinding will have a cross section about 145×45 mm.** Depending on how much the weight and volume of different breeds change compared to the initial, distinguish:**

- Fighter drying – larch, birch, linden, beech;
- Middle-drying – most coniferous rocks, aspen, ash;
- Low-breathing – alder, poplar, Iva.

## Mass cube wood of various breeds

The main method of pre-calculating the weight of the wood cube – **tabular**. In reference books, the density of wood density of various breeds (knowing which is easy to calculate the mass) or the weight values directly.

**For example, using reference tables, we learn how much the initial weight of freshwater wood differs from the weight of the material dried to 20% humidity:**

- The cubic meter of an oak of a cherry initial humidity (about 70%) weighs 990 kg, and at a humidity level of 20% weight decreases 1.4 times – up to 720 kg;
- The cubic meter of freshly served birch fluffy weighs 930 kg (humidity 78%), and after drying to 20%, the weight of the material decreases by about 30% – to 650 kg;
- The mass of the firing wood cube with the initial humidity of 91% is 710 kg – it is 36% more than with a humidity of 20% (460 kg);
- cube weight of fresh larch wood – 1000 kg (humidity 82%), and air-dry (with a humidity of 20%) by 31% less – 690 kg;
- With initial humidity (82%), the aspen cube has a mass of 760 kg, and with 20% humidity, the material becomes easier by 33% (510 kg);
- The cu is freshly (88% humidity) pine weighs 800 kg, when drying up to 20%, the mass is reduced by 1.5 times – up to 520 kg;
- When drying from the initial level (78%) to 20% humidity, the weight of the cubic meter of ash, the manchursky decreases by 300 kg – from 980 kg to 680 kg;
- Mass cube Fir Siberian natural humidity (101%) – 630 kg, and with a humidity of 20% 1.6 times less – 390 kg;
- The weight of the lime wood cube with a decrease in humidity from the initial (60%) to the air-dry level decreases by 23% – from 660 kg to 510 kg;
- The cubic meter of fresh beech wood (64% humidity) weighs 910 kg, and with 20% humidity – by 24% less (690 kg);
- Cubic meter of fresh alder (84% humidity) after drying it becomes easier by 1.5 times – from 810 kg to 540 kg.

**These data clearly show that the difference in the weight of freshly dredged wood and air-dry is essential – by about 30% or 1.5 times.** When working with reference books, it is important to take into account that the values are given for a dense cube (if the entire volume M3 was evenly filled with material). But in fact, even with the tight laying, the gaps between the boards or logs remain. Therefore, the actual weight of the folding cube may differ from the table, and the difference is the more significant than the more the geometry of the material differs from direct lines.

Therefore, to accurately calculate, not only the tree of wood, but also the type of material, depending on which their correction coefficients and calculation methods may be required.

## Features of calculation

Consider the features of the calculation for the most sought-after types of materials. To calculate the weight of lumber of rectangular or square section (edged, profiled, stringent board, timber), the formula is used: the volume * density, where the volume is calculated by the formula length * Width * height. In this way, the weight of one board is calculated, then multiplied by the number of boards in the cubic meter. **For example, we calculate how much the freshly smelted pine board 50x150x6000 mm will be wearing with a humidity of 40% (the density of pine at this humidity takes from the directory – 590 kg / m3).**

- (6 m * 0.05 m * 0.15 m) * 590 kg / m3 = 26.6 kg – the weight of one board.
- 26.6 x 22 = 585.2 kg – cubic meter weight.

**For comparison with humidity of 20%:**

- (6 m * 0.05 m * 0.15 m) * 520 kg / m3 = 23.4 kg – weight of one board;
- 23,4 x 22 = 514.8 kg – cubic meter weight.

By such an algorithm it is easy to calculate the weight of the cubometer of the board or timber of the desired size – 50x200x6000 mm, 40x150x6000 mm, 50x100x6000 mm, 150x50x6000 mm, 50x50x6000 mm and other.

Unedged board can not be put in stacks as tight as a rectangular circuit board, moreover, materials in the party may vary in size.** In order to calculate the weight of the material cube materials, you need:**

- selectively measure the dimensions of materials in the party;
- Calculate the average arithmetic log log or boards;
- calculate the weight of one board;
- Multiply the average weight of the number of boards in the party.

If the battery is too big, and there is no possibility to calculate the number of boards or logs, use the batch method of determining weight – determine the amount of packaging, to which lumber is placed, then lower coefficients are used to calculate weights (specified in OST 13-24-86).

To calculate the weight of the cube of firewood, the batch method also uses, but it must be borne in mind that their laying rules are rigidly standardized. **If the firewood is laid in bulk, when calculating you need:**

- Translate the volume of the bulk cube to the shareholder;
- Calculate weight by applying a lower ratio from GOST 3243-88.

For example, to transfer to the share cube of the volume of crushed wood hardwood, 25 cm long, a ratio of 0.7 is usually applied. If they, for example, bottled into the standard Body ZIL-130 with low sides, then to find out the volume, the volume of the body is 5.98 m3 to multiply to this coefficient. The resulting value is 4.1 m3 – the volume of firewood, neatly laid in a field. The weight of such firewoods from birch at 40% humidity – 2274.6 kg (4.1 m3 x 730 kg / m3 x 0.76), where 0.76 – correction coefficient), and the weight of the cubic meter – 554.8 kg.

**For round sawn timber, the calculation rules are defined by GOST 2292-88 and GOST 2708-75.**

- To calculate the volume of one rounded logs, the cabin of GOST 2708-75 is used.
- For raw logs selectively measure the dimensions of a certain number from the party, determining the diameter of the top (thin) edge excluding the bark. On the basis of the average indicator make further calculations.

To calculate the weight of bulk materials (sawdust, chips) use correction coefficients from the corresponding reference tables.