Plywood refers to a board of wood that is produced by arranging thin sheets of wood by applying formaldehyde, melamine, or phenolic glue. This ensures that the layers do not split even when hammered with a nail. There are a number of factors that would determine the quality of the plywood and the plywood grades.
Plywood is one of the versatile building materials that can be used in everything from furniture to house construction. It is a wooden panel made by stacking of several thin layers of wood veneers. Plywood is used in almost all the furniture like sofa, cupboards, kitchen cabinets, drawers, etc.
When you are going to buy plywood from the shop, you may hear about different grades of plywood such as BWR plywood, MR plywood, BWP plywood, etc.
What Is Plywood?
Plywood is a manufactured wood product made from thin layers, also called “plies,” of wood veneer. These veneers are glued together, with each layer, or ply, having its grain rotated 90 degrees to its adjacent layer.
The grains are rotated for 3 reasons:
- Prevent splitting when nailed;
- Avoiding, or at least reducing, expansion and contraction from changes in its environment; and,
- Providing integrity to the strength of the plywood consistently in all directions across the board.
What Are The 5 Grades Of Plywood?
Plywood grades refer to the quality and appearance of the sheet’s face and back plies. There are grades, and within grades, there are grades. It’s not necessarily as confusing as it sounds, though. Let us explain.
The grade chart, first grades, if you will, are:
- A grade. Highest quality, most expensive. Sanded smooth, surface will be blemish free, and paintable. This is the top of the line plywood.
- B grade. A solid surface, also sanded smooth but with some flaws in appearance. Repairs will have been made and will show as football-shaped patches or wood filler. While some knots may show, no wood is missing. Less expensive than A grade.
- C grade. Unsanded and with some defects apparent that you will have to repair yourself, including splits and knots up to 1 ½ inches, with wood missing. Discoloration is common. To be used when the sheets will not be seen, such as in floorboards.
- D grade. Also unsanded, with defects you might have to repair yourself, including splits, knots up to 2 ½ inches with wood missing, and discoloration. This is the least expensive plywood, and again, to be used where it will not be seen.
Grades of Plywood
01. Moisture Resistant (MR) Grade Plywood
MR grade plywood means moisture resistant plywood. It is also known as commercial plywood. Remember that ‘moisture resistant’ does not mean ‘waterproof’. It means that the plywood is capable of resisting humidity and moisture, and it is not resistant to water.
MR grade plywood is an interior grade of plywood therefore it is suitable for indoor use, not for exterior.
The thickness of moisture resistant plywood is 3mm, 4mm, 6mm, 8mm, 12mm, 15mm, 18mm, 21mm, 25mm as per IS 303. It is less costly as compared to BWR grade of plywood. The price of such plywood approximately ranges from Rs.40 to 189 per sq.ft.
02. Boiling Water Resistant (BWR) Grade Plywood
BWR grade plywood means Boiling Water Resistant Plywood. It is a waterproof plywood. It can resist water better than MR plywood. BWR plywood is glued using phenol formaldehyde adhesive (phenolic resin), which is a synthetic plastic resin. This synthetic plastic resin helps in making plywood waterproof. It is not 100% waterproof as compared to BWP plywood.
Boiling water resistant plywood is an exterior grade of plywood. Therefore, it can be used for furniture that likely to get wet, i.e. kitchen cabinet, lawn chairs, garden tables, etc.
As per IS 303, the thickness of BWR plywood is 4mm, 6mm, 9mm, 12mm, 16mm, 19mm, 25mm. BWR grade plywood is more expensive than MR plywood. The price of this type of plywood is around Rs.50 to 267 per sq. ft. It is the best-selling plywood grade in India.
03. Boiling Water Proof (BWP) Grade Plywood or Marine Grade Plywood
BWP grade plywood means Boiling Water Proof Plywood. It is popularly known as Marine Grade Plywood. BWP plywood is made up single select hardwood species and bonded with boiling water proof synthetic undiluted phenol formaldehyde adhesive. It is superior grade of plywood which is higher in quality and strength as compared to both MR and BWR plywood.
It is the best choice for marine applications such woodwork for building ships and boats.
The thickness of boiling water proof plywood is 6mm, 9mm, 12mm, 16mm, 19mm, etc. as per IS. The price of this type of plywood is approximately ranges from Rs. 52 to 300 per sq.ft.
The factors that determine the quality of the plywood
The factors that determine the quality of the plywood which is important for assigning plywood grades as well include
Overlappings- The lesser the overlapping of sheets in the plywood, the better the quality of the plywood.
Core gaps- If it is greater than 2mm-3mm, it is indicative of poor quality and thereby falls under the lower plywood grade listing.
Nail holding capacity- This feature has got to do with the functionality of the plywood board. if the plywood chips or splits, it is indicative of poor quality.
Weight- The heavier, the board is, the better its quality.
Enquire Now for Exterior Doors
Certifications- In India, plywood is certified by the Indian Institute of standards. According to them, the various standards stand for different plywood grades. Which includes
- IS: 303- which is for commercial ply
- IS: 710- which is for Marine Ply
- IS: 1659- which is for blackboard
- IS: 2002- which is for flush door
- IS: 4900- which is for Shuttering plywood
The grades of plywood
The plywood grades you can access in the Indian market include
MR Grade Plywood The MR here refers to moisture-resistant plywood. This is one of the most common types of plywood that carries the Indian standards specification number IS:303. You should not confuse the term moisture resistant with waterproof. MR plywood is by no means waterproof in nature it can merely resist moisture and humidity.
BWR Grade plywood- The term BWR refers to boiling water poof plywood. It is suitable for both interior and exterior use and is most suitable for making kitchen cabinets, furniture, paneling etc.
BWP – This refers to boiling waterproof boards that are almost similar in construction and glue used to the BWR plywood grades. But, one distinguishing factor is that BWR refers to plywood grades while BWP stands for blockboard grade.
The face grade of plywood is always the first designated:
AA has two A grade faces.
AD has an A grade face and a D grade back.
S Selected grade, equals or betters B grade.
BB has two B grade faces.
CD has a C grade face and a D grade back.
DD has two D grade faces.
A High quality face, suitable for clear finishing.
B High quality surface suitable for painting.
S High quality surface suitable for painting.
C Non appearance grade with a solid face, not meant to look attractive.
D Low appearance grade with permitted defects.
PG Non-structural, for packing use, unsanded rough appearance.