Plywood: sheet dimensions and thickness, types, price, characteristics

Of the sheet building materials, the oldest is plywood. It has been in production for several decades. And, although it is crowded by other more modern materials, it still has its own segment in the market. All this is due to its properties, a large assortment both in size and thickness. What size and thickness of plywood can be, we’ll talk about grades and classification today. 

Types of plywood and its classification

Plywood is a long-known and popular sheet building material. It has high bending strength, both in the longitudinal and transverse directions. In private households, it is used for sheathing frames, flooring. Cheap grades are also used in some building processes.

Plywood is made from several layers of veneer glued together.

Veneer – wood material, which is thin sheets of wood with a thickness of 0,1 to 10 mm.

Fiber layers arranged in different directions. This increases the bending strength of the material in all directions.

Plywood is made from softwood and birch. Birch is more expensive, more often used as furniture. Coniferous is made from wood of all coniferous species. Cheaper options – from larch, pine and spruce – can be used both for the manufacture of furniture and for construction needs (for example, for sheathing a frame or for removable formwork in the manufacture of concrete products). Can use Siberian cedar veneer. This type usually goes as a finishing material.

Layers and their number

There are at least three layers in plywood, but there may be more. The layers are arranged so that the veneer fibers are directed in different directions – alternately either along the long side of the sheet, or across. An odd number of veneer layers is more common. In private housing construction, three and five-layer plywood is most often used. In this case, the orientation of the layers is selected relative to the central layer.

If on the outer layer the veneer fibers are directed along the long side, the plywood is called longitudinal. It has great flexibility. If the veneer fibers are located along the short side of the sheet, the plywood is called cross ply and is used where high bending rigidity is required.

Water Resistance

Since glue is used in the manufacture, the entire material has a fairly high degree of water resistance. There are several popular brands of plywood:

• Moisture resistant is marked FC. For its bonding, an adhesive based on urea-formaldehyde resin is used. That is, there is the emission of formaldehyde. With emission class E1 and below, it can be used indoors or for the manufacture of furniture.
• Plywood of increased moisture resistance – FSF. The same glue is used only with water-repellent additives. Can be used for outdoor work.
  

• FSF-TV. The same water-repellent plywood but with fire-resistant additives.
• Laminated – practically insensitive to moisture.

If you need material for indoor use and don’t want to worry about formaldehyde in the air, look for the FBA grade. It is environmentally safe, but only suitable for rooms with normal humidity. The FB brand does not swell even under water, there is also BS aviation plywood. She still does not react to chemical environments. It was used in the construction of ships and airliners.

Degree of surface treatment

The outer layers of plywood can be sanded at the factory. There are such types:

• Unpolished. There is no surface treatment. Marked with NSh.
• Only one side has been sanded smooth. Sh1 is added to the marking.
• Both sides are polished – Ш2.
  

Sanded on both sides, plywood is used to make furniture. For construction, both smooth sides are rarely needed. Usually, if polished is used, then Sh1. And then, if this material is used for decorative trim. More often at a construction site, unpolished is needed – it provides better adhesion to other materials.

Varieties and markings

There are five types of plywood. The highest is E (Elite), and further, as it deteriorates, from I to IV. The grade is determined by the state of the upper – front layers. Moreover, the quality of both surfaces is separately assessed and written through a slash (slash). For example, I/II or III/IV.

In GOST, it is described in detail for which grade what surface errors are permissible, there are special tables according to which this grade is determined. If at least one parameter is worse than the allowable one, the grade is reduced.

Here are the features on the front surface that plywood of different grades can have.

• Elite. For this brand of plywood, the veneer must be perfect. There may be only minor changes in the wood (not peepholes). All. There should be no other disadvantages.
  

• I sort of. Can be
  • Knots:
    • pins, no more than 3 pieces per square meter;
    • healthy, fused, dark and light with a diameter of 15 mm, no more than 10 pcs / m², they may have cracks no more than 0,5 mm wide;
    • partially fused, not fused, falling out with a diameter of not more than 6 mm in an amount of not more than 3 pcs / m²;
  • Closed cracks no more than 200 mm long and no more than 1 mm of sheet width.
  • Healthy discoloration – no more than 5% of the area.
    

• II сорт. Allowed:
  • Knots:
    • pin without restrictions;
    • healthy, fused, dark and light with a diameter of 25 mm, no more than 5 pcs / m², they may have cracks no more than 0,5 mm wide;
    • partially fused, not fused, falling out with a diameter of not more than 6 mm in an amount of not more than 6 pcs / m²;
  • Closed cracks no more than 200 mm long and no more than 1 mm of sheet width.
  • Open cracks with a length of not more than 200 mm, a width of not more than 2 mm in an amount of not more than 2 pcs when smeared with putty.
  • Healthy discoloration is allowed.
  • Overlap in the outer layers with a length of not more than 100 mm in the amount of not more than 1 pc per 1 m of the sheet.
  • The leakage of glue is not more than 2% of the sheet area.
  • The torn-out fibers are not more than 5% of the sheet area.
  • Scratches, dents are allowed by depth (height) within the limits of maximum deviations in thickness.
  • The gap in the joints with a width of not more than 1 mm, not more than 1 pc per sheet.
  • Wood inserts no more than 8 pieces per 1 m².
  • Double insert – no more than 2 pieces per m².
    

• III grade.
  • Knots:
    • pin without restrictions;
    • healthy, fused, dark and light with cracks no more than 1,5 mm wide;
    • partially fused, not fused, falling out with a diameter of not more than 6 mm in an amount of not more than 10 pcs / m²;
      

      

  • Closed cracks without restrictions.
  • Open cracks
    • length no more than 300 mm no more than 2 pieces,
    • length not more than 600 mm, width not more than 5 mm in the amount of not more than 2 pcs when smeared with putty;
  • Healthy discoloration is allowed.
  • Overlap in the outer layers with a length of not more than 200 mm in the amount of not more than 2 pc per 1 m of the sheet.
  • The leakage of glue is not more than 2% of the sheet area.
  • The torn-out fibers are not more than 15% of the sheet area.
    

    

  • Scratches, dents are allowed by depth (height) within the limits of maximum deviations in thickness.
  • The gap in the joints with a width of not more than 2 mm is not more than 1 piece per meter of the sheet.
  • Wood inserts and double insert – no restrictions.
  • Non-ferrous metal brackets are allowed.
• IV grade may have such defects.
  • Knots:
    • pin;
    • healthy, fused, dark and light without restrictions;
    • partially fused, not fused, falling out with a diameter of not more than 40 mm without restrictions;
  • Closed cracks without restrictions.
  • Open cracks
    • length no more than 300 mm without restrictions;
    • length no more than 600 mm, width no more than 10 mm without restrictions;
      

      

  • Healthy discoloration is allowed.
  • Overlapping in the outer layers is allowed.
  • Adhesive seepage is allowed.
  • Torn fibers are allowed.
  • A gap in the joints is allowed.
  • Scratches, dents are allowed.
  • Wood inserts and double insert – no restrictions.
  • Non-ferrous metal brackets are allowed.

If there are defects that are not listed in GOST, the product is considered off-grade. It is also considered out-of-grade if the maximum allowable size of defects is exceeded. Sometimes they try to sell such products as the fourth grade, but this is a regrading and the price for it should be much lower.

By the way, if there are no obvious cracks and knots that have fallen out, the third grade can be used for interior decoration. In certain interiors, it looks even more interesting than E or the first, which are just a flat sheet without any of the features inherent in wood.

Plywood: sheet dimensions, thickness

For different jobs, sheet material of different sizes may be more convenient. And plywood is no exception. It is produced in different sizes, which are usually divided into standard and not. Standard ones are prescribed in GOSTs (GOST 3916.1-96), non-standard ones are produced on order – for large companies or those formats that are more in demand in retail. Usually a sheet of plywood is in the form of a rectangle, but it can also be in the form of a square.

Standard plywood dimensions

In general, different types of plywood are described by different GOSTs (GOST 2707, GOST 20907, GOST 102-75, GOST 3916.1-96) and they contain different size grids.

The most popular small-format plywood sheets have the following standard sizes:

• 1220*1220mm;
• 1525*1220mm;
• 1525*1525 mm.

Small sheets of plywood are good because you can work with them without helpers. But a large number of seams is not good.

According to GOST 3916.1-96, it is allowed to manufacture plywood of non-standard length by agreement between the manufacturer and the consumer.

In theory, combinations from the specified list can be any. In practice, they are much less.

Large format

In some cases, it is more convenient to use large plywood sheets – the joints become much smaller. Most often, large format plywood is used in the following sizes:

• 1830*1525mm;
• 3050 * 1525mm
• 3000*1500mm;
• 2500*1250mm;
• 2440*1220 mm.

No one has brought order to the standards, so theoretically you can find almost any size of those that fit into one of them. So, for example, according to GOST 102-75:

• The length of the plywood sheet can be from 1000 mm to 1525 mm. The length change step is 25 mm.
• The width can be from 800 mm to 1525 mm with the same gradation step – 25 mm.

Moreover, the maximum deviation in length and width is 4 mm. The thickness of plywood can be from 1 mm, but this is a rare “aviation” brand. Regular is available in thicknesses from 3 mm to 30 mm, but you can find up to 40 mm. Permissible error in dimensions for thickness – 0,5 mm.

If you look at the more recent standard 3916.1-96, it specifies a different grid of plywood sizes with a specific enumeration of possible values ​​​​(see table above).

Thickness

With the thickness of plywood, the picture is about the same: if desired, you can find from 1 mm to 40 mm thick. It is possible that there are thicker options. But most often there are plates with a thickness of 6 mm to 27 mm.

By the way, it is interesting that in any of the standards the maximum allowable deviation is prescribed – 0,5 mm. Which, taking into account not always a large figure, is not so small. And this deviation can significantly complicate the installation of the material on the floor. The difference has to be corrected with thin pads, or, if it is small, sanded at the joints with a grinder.