All about the assortment of lumber

When choosing timber independently, it is necessary to take into account its grade, since the consumer characteristics of industrial timber differ. In the material of this article, we will consider the basic requirements, processing methods, the difference between varieties and the main nuances of choice.

Lumber includes wood of various sizes and qualities. In the course of its manufacture, the logs are divided into parts and cut out. Each type of lumber is subject to generally accepted government standards. (for example, GOST 24454-80, GOST 8486-86, GOST 2140-81, etc.).

The quality of export and on-farm edged materials is assessed by the face or the worst edge. At the same time, attention is paid to a number of important criteria:

• material defects (roughness, cracks, structural imperfections);
• permissible humidity value;
• the quality of the cut and the angle of its inclination;
• wood density and core quality;
• the number of knots per unit area of ​​the material;
• the appearance and shade of the blanks;
• the age of the material, the place of its cutting;
• damage by insects (bark beetles, beetles);
• the presence of fungus, mold, rot;
• warping along the edge;
• spiral curvature.

GOST prescribes the requirements for such types of wood as fir, cedar, spruce, poplar, pine, linden, aspen, alder, birch, beech, ash, larch, oak, hornbeam. With regards to knotty, knots are not taken into account, the area of ​​which does not reach half of the tolerance. However, the higher the grade, the more stringent the grade requirements.

The same requirements apply to cracking of workpieces along the edges and facets. Cracks should not cause damage to the integrity of the lumber.

By the type of processing, lumber is planed, chipped, round, peeled, sawn. Based on the type of sawing, timber is divided into tangential and radial. The workpieces of the first group are created by cutting along lines that do not touch the core. Analogs of the second group are sawing through it.

Faceted lumber is treated wood with a specific length. Untrimmed analogues do not have processing from the front side. Calibrated varieties are dried to a specified moisture value, processed to specific sizes. Structural ones are obtained from hardwood (oak, larch).

All sawn timber subjected to sorting is divided into 2 types: edged and unedged. Each species has its own characteristics.

The workpieces of the cut group have a regular rectangular shape. They are made by planing (by removing shavings from both edges or from one plane). Each such board is a single, bark-free wood sheet with smooth edges. Thanks to high-quality grinding, such lumber is installed directly at the selected place, without subjecting it to additional processing.

Unedged material has rough edges. Its surface is smooth on both sides, on the sides there are untreated areas of a rounded shape, covered with bark. Such lumber has the worst appearance, it costs 2-3 times cheaper than the edged counterpart. The cross-section of such blanks is rectangular or square.

There are several types of lumber. The grade depends on the quality of deciduous or coniferous wood and its processing. Deciduous materials are divided into 4 varieties, the classification of conifers consists of 5 (a selected variety is added).

The best grade is considered to be selected lumber. High-grade wood (grade 0) is used in shipbuilding, automotive, furniture production. It has no defects (knots, stepchildren, through and deep cracks, remnants of tree bark, rot, wane, roots). Foreign inclusions are excluded, the inclination of the fibers is 5%, the burrow is one-sided. Minimal shrinkage cracks are allowed.

First-class lumber is used in the construction and furniture industry... This is the most popular product with a minimum of defects (knots, cracks). It does not have dry, loose, dropped knots, healthy twigs, cracks more than 1 cm wide and deep. The total length of cracks should not exceed 1⁄4 of the length of the workpiece.

It does not have rot, through cracks and germs, mold, and other elements. Sapwood is excluded, timber of the first grade does not have blue stain, rottenness, traces of parasites, dark spots.

The second-grade lumber used in furniture production has more defects than its selective counterpart. They are subject to less stringent requirements, so their quality is lower. These blanks can have cracks with a total length of up to 1/3 of the board length, as well as knotty with a small knot diameter. The presence of 2-3 traces of wormholes per 1 m of length (or 1 large) is allowed.

The timber of the second grade should not have mold, mildew, traces of rot, through cracks and crevices. Its differences with the products of the first grade are small. Drop-out, rotting knots are excluded, the size of healthy ones should not exceed 2 cm. Rotteness is not allowed, mechanical damage, as well as foreign inclusions, are excluded.

Lumber of the third grade is used for the manufacture of transport packaging and containers (including disposable boxes, flooring, pallets). In fact, these are trimmings from grade 1 and 2 lumber. The volume of defects is even greater here, this is low quality wood, characterized by a low cost.

The main requirement for such material - absence of large intergrown knots and deep end cracks. A sharp angle of inclination of the fibers, mechanical damage to the wood layer, mold, wormhole are allowed. The presence of internal sapwood, browning is possible.

Lumber of the fourth grade can have almost all the defects specified in GOST, including waviness and warpage... In this case, the length of the cracks, the size of the knots can be any. The number of wormholes should not exceed 6 per 1 m of the workpiece. Such material is used for the production of fences, formwork, pallets, utility blocks, change houses, sheds, gazebos.

He may have a color change, as well as mechanical damage. Wane of the upper layer and winging are also allowed. The presence of rot and foreign inclusions is excluded. The integrity of the foundation must be maintained. The surface may be rough, there may be intergrown knots.

The assortment of lumber supplied to the domestic market is diverse, which often baffles the average buyer. There are a number of factors to consider when purchasing timber.

• Planks and bars can have 5 grades, and beams only 4.
• The moisture content of the sawn timber should not exceed 22%. If it is larger, it will not be possible to dry the wood.
• The workpieces have different roughness. The higher its indicator, the lower the grade.
• The material should not have large deviations from the length.
• The priority is for breeds grown in a cold climatic zone.

The varieties differ from each other not only in price and quality. When buying, you need to consider the scope.As a rule, the first 3 grades are suitable for construction, the lower ones are used for cladding and flooring. You should not buy selected lumber for cases where second-rate or third-rate raw materials are used.

Lumber for outdoor use should be free from through and deep cracks. The more knots a wood has, the worse its mechanical characteristics. The roughness of a quality material should not exceed 1250 microns. Dense edged material is stronger and more moisture resistant.

Sorted sawn timber is marked at the end in the form of a “0” icon, dots or lines (from 1 to 3). At the same time, only products of the 4th grade are not marked. Marking can be designated by numbers and letters "A", "B", "C". Lumber up to 2.5 cm thick is marked with lines, thicker - with dots.

The material is checked for flaws before entering the warehouse.... In addition to standard control, when buying, you need to pay attention to varietal characteristics. It is best to purchase material from a trusted supplier. The grade is determined on any 1 m board from either side. In this case, the variety is determined by the worst side.