Plywood

Plywood is a multi-layered building material made by gluing specially prepared birch and alder veneer sheets. The number of veneer layers is 4 or more. To increase the strength of plywood, veneer layers are superimposed so that the wood fibers are strictly perpendicular to the previous sheet.

Plywood grade descriptions:

 I grade

Not allowed:

  • pin knots, overlap in the outer layers, cracked rifts;
  • light and dark growth, unhealthy discoloration, decay;
  • the presence of adhesive tape, the leakage of glue;
  • scratches, dent, imprint, comb, tearing out of fibers, polishing, metallic inclusions, gap in joints, delamination, bubbles, zakorin, wood inserts, double inserts.

Allowed:

  • healthy accrete dark and light knots with a diameter of not more than 15 mm in the amount of 5 pcs. on 1 m2 of sheet surface with cracks no wider than 0.5 mm wide;
  • partially accrete, non-accrete, falling out knots, holes from them, a wormhole with a diameter of not more than 6 mm per 1 m2 of leaf surface not more than 3 pcs .;
  • closed cracks no longer than 200 mm in the amount of not more than 2 pcs. on 1 m width of a leaf;
  • a slight deviation of a random nature in the structure of wood, except for dark eyes;
  • healthy discoloration of not more than 15% of the leaf surface, slight waviness;
  • chopes with a diameter of not more than 6 mm per 1 m2 of sheet surface no more than 3 pcs .;
  • shortage of veneer, edge defects when grinding and trimming no more than 2 mm wide;

Grade II

Not allowed:

  • unhealthy discoloration, decay, abrasion, metallic inclusions, gap in joints, delamination, blisters, jar;

Allowed:

  • pin knots, healthy accreted dark and light knots with a diameter of not more than 25 mm in the amount of 10 pcs. on 1 m2 sheet surface with cracks no wider than 1 mm wide;
  • partially accrete, non-accrete, falling knots, holes from them, a wormhole with a diameter of not more than 6 mm per 1 m2 of leaf surface not more than 6 pcs .;
  • closed cracks no longer than 200 mm in the amount of not more than 2 pcs. on 1 m sheet width, split cracks no more than 200 mm long, no more than 2 mm wide in the amount of not more than 2 pcs. subject to sealing putty;
  • light growth, dark growth with a diameter of not more than 25mm in an amount of 10 pcs. on 1 m2 sheet surface with cracks no wider than 1 mm wide;
  • a deviation in the structure of wood, a healthy discoloration of no more than 15% of the surface of the sheet, slight waviness, scratches;
  • punctured with a diameter of not more than 6 mm per 1 m2 of the sheet surface not more than 6 pcs .;
  • overlap in the outer layers no longer than 100 mm in the amount of not more than 1 pc. on 1 m sheet width, shortage of veneer, defects of edges when grinding and trimming no more than 5 mm wide;
  • the presence of adhesive tape in unpolished plywood, the infiltration of glue no more than 2% of the surface of the sheet;
  • a dent, imprint, scallop within the limits of maximum thickness deviations, tearing of fibers no more than 5% of the sheet surface, slight waviness;
  • wood inserts for repairing knots and holes when seeding in an amount of not more than 8 pcs. per 1 m2 of sheet, broken cracks - no more than 30 mm wide, no more than 300 mm long in the amount of not more than 1 pc. on 1 m width of a leaf.

Grade III

Not allowed:

  • unhealthy discoloration, rot, delamination, blisters, zakorin.

Allowed:

  • pin knots, healthy accreted dark and light knots with cracks no more than 1.5 mm wide;
  • partially accrete, non-accrete, falling knots, holes from them, a wormhole with a diameter of not more than 6 mm per 1 m2 of the sheet surface not more than 10 pcs .;
  • closed cracks, split cracks no more than 300 mm long, no more than 2 mm wide, not more than 2 pcs. on 1 m sheet width (allowed with a length of up to 600 mm, a width of up to 5 mm), provided the seal with putty;
  • light growth, dark with cracks no more than 1.5 mm wide;
  • a deviation in the structure of wood, a healthy discoloration, a slight waviness, scratches;
  • punctured with a diameter of not more than 6 mm per 1 m2 of the sheet surface not more than 10 pcs .;
  • • overlap in the outer layers no longer than 200 mm in the amount of not more than 2 pcs. on 1 m sheet width, shortage of veneer, defects of edges when grinding and trimming no more than 5 mm wide;
  • the presence of adhesive tape in unpolished plywood, glue penetration not more than 5% of the surface of the sheet;
  • a dent, imprint, scallop within the limits of thickness deviations, tearing of fibers no more than 15% of the surface of the sheet, grinding of no more than 1% of the surface of the sheet, waviness (for polished plywood), hairiness, ripples;
  • a gap in the joints with a width of not more than 2 mm in an amount of not more than 1 pc .;
  • wood inserts for repairing knots and holes, for repairing split cracks - no more than 50 mm wide, no more than 500 mm long in the amount of no more than 2 pcs. on 1 m width of a leaf.

Grade IV

Not allowed:

  • rot, delamination, blisters, zakorin.

Allowed:

  • pin knots, healthy accreted dark and light knots, partially accrete, non-accrete, falling out knots, holes from them, wormhole with diameter no more than 40 mm, closed cracks, broken cracks no longer than 600 mm, width no more than 5 mm;
  • light and dark growth, deviation in the structure of wood, healthy and unhealthy discoloration;
  • pricked with a diameter of no more than 40 mm, overlap in the outer layers, lack of veneer, defects in edges when grinding and trimming no more than 5 mm wide;
  • the presence of adhesive tape in unpolished plywood, glue penetration, scratches, a dent, imprint, comb, tearing out of fibers, polishing, non-ferrous metal brackets;
  • clearance in joints not more than 5 mm wide, waviness (for polished plywood), fleecy, ripples, wood inserts for repairing knots and holes, for repairing broken cracks.

For all varieties

  • pork warping of up to 6.5 mm is not taken into account, a thickness of 6.5 mm and more is allowed with a deflection of no more than 15 mm per 1 m of the diagonal length of a sheet of plywood;
  • surface roughness for ground

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