What You Need To Know About Plywood
Today, plywood is used for just about everything. In fact, carpentry works which usually take up the most chunk of the renovation costs probably use solid wood in combination with plywood.
Interior Designer: Inside Living
What is Plywood?
Plywood is an engineered wood from the family of manufactured boards. Plywood is made from thin layers of wood veneer, with adjacent layers perpendicular to each other which are held together by glue.
By laying the layers at right angles to each other, their wood grain is cross-grained and thus reduces the tendency of wood to split when nail are used on the edges. This also provides stability and strength since it reduces the expansion and shrinkage.
Do You Know?
Usually an odd number of layers or plies is used to reduce warping. The more layers that are used in the plywood means more cost.
However, not all plywood is made the same. Thinner and lower quality plywood may only have their plies arranged (and not the wood grain) at right angles to each other whilst better quality plywood products may have five plies in steps of 45 degrees for extra durability and strength in multiple axes.
Plywood Vs Solid Wood
Although solid wood is much stronger than plywood, due to changes in the atmospheric humidity, it will still lose its strength due to the expansion and contraction of the wood. Although the plywood is considerably more flexible, the plywood layers may separate in a damp environment due to the long exposure to moisture. In addition, softwood plywood is often used for curve forming applications which cannot be easily achieved with solid wood.
Interior Vs Exterior Plywood
Interior plywood is moisture resistant and used for interior use only. Their applications include furniture, sheathing of walls, building of cabinets and so on. Exterior plywood is much sturdier, moisture and fungal resistant with negligible core gap than interior plywood. Their usage may include wet environments where it is exposed to moisture for long periods, such as in coastal areas or aboard ships.
What are Plywood Grades?
Plywood grades are determined by the wood discolorations, surface defects, resistance to moisture and strength and grading rules are different based on the country of origin. The most common standards are the British Standard (BS) and the American Standard (ASTM).
Do You Know?
The significance of the rating is that the grade determines the type of application the plywood is suited for.
Plywood can be of grade A, A/B, A/BB, B, B/BB, BB and so on.
Grade A plywood, which is the best grade, has no jointed veneers and is free of major defects such as knots, knot holes, discoloration and cracks. Grade B plywood has minor defects such as discoloration or small knots. Whilst Grade BB plywood permits jointed veneers, large knots, plugged knotholes and minor cracks and so on.
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Image from columbusmillwork
Do You Know?
The use of one letter in a plywood grade indicates that the face and the back of the sheet are of the same grade. Two letters divided by a slash indicate the face and back are of different grades.
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