Construction plywood is a multilayer material from glued veneer sheets. It happens of different types that differ in purpose, type, shelf life, price. Plywood is used for formwork, rough floors, interior decoration and building envelopes.
Benefits
Pros:
- High strength, ability to withstand heavy loads. Multilayer sheets are used as formwork of massive reinforced concrete structures.
- Service life - up to 50 years.
- Universality. It can be used both in the construction of the foundation, and when installing the roof.
- Ease of handling. The material is sawn into fragments of any configuration. Wood is attached to surfaces with hardware: nails, screws, screws and others.
- The veneer surface can be sanded, painted, wallpapered, covered with ceramic tiles. The material is impregnated with antiseptics, treated with varnish.
- Low specific weight of glued veneer products.
- You can create rectilinear and curved products.
- Laminated plywood is used as a finish for walls and ceilings.
- The material practically does not crack, through cracks to the entire depth of the massif are excluded.
- Low price.
Classification
For the division of building plywood into types, the following indicators are used:
- appearance,
- sizes
- production material
- the number of layers of veneer,
- adhesive impregnation
- surface treatment,
- varieties.
Appearance
By the nature of the front surface, longitudinal and transverse sheets are distinguished. If the top veneer fibers are located along the length of the sheet, this is a longitudinal product. Across - transverse.
Dimensions
Wood boards are made in accordance with GOST 3916.1-96 and GOST 3916.2-96. Plywood sheets should be of a standard type, large-format.
Standard type, mm | Large format, mm |
1550 x 1550 | 1830 x 1525 |
1525 x 1525 | 2440 x 1220 |
1525 x 1350 | 2500 x 1250 |
1525 x 1270 | 1525 x 3050 |
1475 x 1475 | 1500 x 3000 |
1270 x 1270 | — |
1220 x 1220 | — |
Production material
Conifers require the use of the front layer of larch, pine, fir, spruce. The inner layers can be made from hardwood veneers. For decorative decoration of premises, veneer from Siberian cedar is used.
Birch plywood is made on the basis of birch veneer. It is expensive, rarely used in construction.
Sheets of poplar are not manufactured in Russia. The main production is located in China. Products are much cheaper than analogues, but inferior to them in technical characteristics.
Number, orientation of veneer layers
Plywood is made mainly of three, five, seven thin layers of wood. They alternate with the transverse and longitudinal direction of the veneer fibers. This order allows you to increase the strength of plywood. The density of veneers depends on the number of layers..
Glue impregnation
Impregnations with various adhesive compositions improve the quality of sheet materials, affect strength, resistance to fungal, mold, moisture, protect against parasitic insects, provide fire protection. In the marking, the letter designation of the adhesive composition must be indicated:
- FBA Albumin casein glue is used for impregnation. Products are environmentally friendly. However, the products are not water resistant. Therefore, do not use it in rooms with a high level of humidity.
- FSF. For impregnation, glue is used, which includes formaldehyde. Products have increased wear resistance, density, water resistance. Most often used in roofing.
- FSF-TV. Fire retardant components are added to the adhesive. Cookers do not burn, they can smolder slowly. Used where high fire protection is required.
- FC. Urea is used for impregnation. Plywood gets off fences inside buildings and structures. It does not tolerate high humidity.
- FCM. Veneers are glued with melamine and formaldehyde resins. This is the most common type of plywood.
- FB. Bonding sheets is bakelite varnish. It is used at a high level of humidity and under water.
- BS. Special impregnations allow the plates to achieve high technical performance. The material has a second name - aviation plywood. Due to the high price it is rarely used in construction.
- BV. For the same reason as the BS brand, it is not used in construction.
Surface treatment
According to the state of the front surfaces, the sheets are divided into three types:
- NSh - unpolished plywood;
- Ш1 - grinding of one surface;
- Ш2 - grinding of both sides.
Assortment
GOST 30427 divides the plates according to the external condition of the veneer into grades. The main factors that determine the grade according to the state of the woody outer layer are the presence of knots of various structures, cracks of different sizes, depths, color of the porosity, rot, etc. A total of 5 varieties are distinguished:
- E (elite),
The complete absence of defects besides minor flaws in the veneer structure. High quality material used for finishing finishing work.
- 1st
The maximum length of defects should not exceed 2 cm.
- 2nd
Narrow cracking is permissible, not more than 20 cm long. Adhesive release to no more than 2% of the sheet area.
- 3rd,
In addition to the previous drawbacks, no more than 10 wormholes ø up to 0.6 cm per 1 m are allowed2 plate surface. All of the above defects should not be more than nine.
- 4th.
These are products of the lowest quality. There are no restrictions on the presence of certain defects. The main requirement is the integrity of the product.
Construction application
During construction, plywood is used in the following structures:
- formwork
- scaffold,
- roof elements
- rough floors
- facing
- utility material.
Formwork
Plywood is used as formwork panels for pouring concrete mortar for a monolithic foundation of other structures. Only moisture resistant varieties are used. Laminated plywood, which can be used repeatedly, is well suited.
You can build a formwork from bakelite slabs. This is expensive stuff.
Formwork is involved in wet processes, its open ends must be protected with waterproof paint or furniture varnish.
Advantages of wood-laminated veneer slabs over wooden boards:
- Do not deform at a distance of up to 1 m between the uprights.
- After dismantling, an even, smooth surface remains.
- Finishing up to the ideal state of the concrete plane requires a minimum amount of mortar.
- Suitable for multiple use. Easy to customize to a new foundation configuration.
- Due to the smooth surfaces, the use of screw fasteners, the installation and dismantling of the formwork are carried out in a short time.
Scaffold
When scaffolding, plywood is used as scaffolding and flooring. Durable and resilient material does its job well. With large areas of utility barriers of tall buildings, the use of wood boards is economically disadvantageous. When erecting forests around low-rise buildings, the use of plywood is advisable. To do this, choose sheets with a thickness of at least 9 mm. The height of the wood massif of the flooring can withstand static and dynamic loads from workers with various tools and equipment.
Roof elements
For the erection of a roof of complex geometric shape, as the connecting elements of the rafters and beams, sheets of a thickness of 6 mm or more are used. These are, as a rule, materials of the FSF and FB brands.
On the attic floors, rafters and cross ties are faced with sheets of the FSF and FSF-TV brands. They have high moisture resistant and fire retardant characteristics. For the formation of the interiors of the attic rooms, the most suitable material is E.
Rough floors
For leveling, sound insulation, thermal protection of the base of the floor, wood laminated boards with a thickness of at least 9 mm are used. The segments are laid so that the seams of the joints are spaced apart. For fastening use bituminous mastics, synthetic glue.
Draft floors serve as a good base for a laminate with a backing, traditional parquet. A linoleum topcoat on a plywood base creates a smooth surface.
The service life of rough floors is 20-30 years or more. Grade E plywood is laid as a topcoat in the form of large squares. The floor is varnished or painted with moisture resistant enamels.
Cladding
Finishing the inner surfaces of the fencing with plywood creates the effect of natural wood. It is faced with wall panels, partitions, window sills. You can find the interiors of public buildings, trimmed with wood laminate. These are children's, medical institutions, concert halls, restaurants and others.
FSF sheets are facing facades of houses. The lining must be painted with waterproof compounds.
Utility Material
The waste residue of plywood after major construction work is used as an auxiliary material. It is used for the manufacture of small auxiliary parts of any structures or accessories. Small waste is suitable for kindling outdoors. But burning glutinous raw materials can be accompanied by toxic fumes.
Description of manufacturing technology
Plywood manufacturing process:
- Coniferous or birch ridge (trunk) is subjected to hydrothermal treatment.
- In the sawing shop, ridges are cleared of bark and sawn into lumps.
- On a special machine from raw materials peeled veneer. By turning the block, a thin layer of wood is removed with a sharp blade.
- The veneer ribbon is cut into pieces.
- After drying, the segments are sorted by size into lumpy and large-format material.
- They get rid of the defective areas, put in their place high-quality wood.
- At the site of the set of packages, the glued veneer is alternated with dry sheets. The bags are cold pressed.
- The kits are pressed under high pressure and heat.
- Plywood is cut according to the required dimensions.
- The ends are painted to increase the shelf life, polished front surfaces.
- The material is packaged, sent to the finished goods warehouse.
Marking
Decoding the markings of plywood is easy to do. For example, ExSh1 FSF-TV 09x1550x1550 means that the highest grade material is made of coniferous wood (if the letter "x" is absent, then the veneer is made of birch), sanded on one side. The veneer is glued with a composition based on formaldehyde with fire retardant treatment. Sheet size - 1550 x 1550 mm. Thickness - 9 mm.
If the designation DF is added to the marking, then the material is covered with a film of melamine formaldehyde resin, suitable for decorative finishes.
Cost
The average price for some types of plywood is presented in the table.
Brand | Price for 1 sheet, rub. |
1 FSF 09x1220x2440 | 1210 |
E FSF NSh 04x2440x1220 | 557 |
E FC Sh2 08x1525x2325 | 722 |
1 FC NSh 03x1520x1520 | 240 |