Plywood Types – MR resistant, BWR and BWP/Marine ply

Plywood types : Plywood is one of the most versatile, cheap, and commonly used wood alternative for interior works, furniture, kitchen cabinets, shuttering works, etc. Earlier plywood manufactures are limited. They manufacture excellent quality plywood that is durable and long-lasting. Nowadays hundreds of companies have started manufacturing plywood. The densities, qualities, sizes, and standards are compromised and the customers are duped most of the time.

How to select a plywood? Which one is the best?

Also read : WPC boards – Advantages, Disadvantages and uses

Plywood types – What is plywood?

Plywood is a manufactured wood panel/ engineered wood made from thin sliced natural wood called veneers in the core as well as the face. These core veneers are glued in layers one on top of the other with adjacent layers having their wood grains rotated up to 90 degrees to one another. The cross layering of adjacent layers imparts structural strength and stability to plywood. These veneers are bonded together with glue and pressed under high pressure and heated to form plywood. Plywood is a versatile, flexible, and highly workable building material widely used in manufacturing furniture, cabinets, shelves, and wardrobes, etc. They are also used for woodwork for ships and boats and for shuttering works in the construction sector. These are the commonly used categories of plywood based on application sectors.

• Softwood plywood
• Hardwood plywood
• Tropical plywood
• Aircraft plywood
• Decorative plywood
• Flexible plywood
• Marine plywood

Properties and dimensions of plywood.

Usually, hardwood and softwood are used for making plywood. The core will be of an inexpensive wood veneer based on geographical availability whereas the face will be of a quality wood veneer. Plywood is resistant to cracking, splitting, shrinkage, twisting, etc, and got excellent strength and durability. Plywood’s are available in a size of 2449 x 1219 mm (8’x4’) and the thickness ranges between 3 mm to 25 mm based on the manufacturer. The cost and strength of plywood depend on the thickness, grade, type, and the number of veneer layers.

Plywood types, layers & strength

The strength and cost of ply depend on the number of ply layers as they influence production costs and plywood quality. If the number of plies/layers is more, the plywood will be stronger but the production costs will be higher. For example, 18mm plywood of 15 plies is stronger than 18mm plywood of 13 plies. The minimum number of plies in plywood is 3 plies. An odd number of plies in plywood can reduce warping and deformation. Usually plywood of more plies are of premium quality .

Plywood types and grades

Plywood is classified into three types based on the area of applications and water resistant properties.

• MR (Moisture resistant )grade or Commercial ply (IS 303 )
• BWR (Boiling water resistant ply – (IS 303 )
• BWP (Boiling water proof or Marine ply – ( IS 710 )

Moisture resistant (MR grade ) or Commercial ply- IS 303

MR resistance OR Moisture resistance plywood is known as Commercial ply. Moisture resistant or MR resistant ply is an interior grade ply that can withstand some amount of moisture, humidity, and dampness, etc. Commercial ply is not waterproof and is not preferred for areas exposed to direct water contacts. Commercial ply is manufactured using wood veneers from locally available tree species. This change in tree species will not affect the basic properties which will be as per IS 303.

The adhesive used for joining the veneers is Urea-formaldehyde. MR grade plywood is an interior grade of plywood and is suitable for indoor use, not for the exterior and areas in direct contact with water. Moisture resistant grade of plywood has the highest internal density among all the available grades of plywood. MR grade ply is used for almost all interior works like furniture, cabinets, office interiors, partitions, ceiling works, etc.

BWR (Boiling water resistant ply) -IS 303

BWR grade plywood is Boiling Water Resistant Plywood confirming to IS 303. Boiling water resistant plywood is an exterior grade of plywood that can resist water better than MR grade commercial ply but is not 100% waterproof. The veneers are glued by Phenol formaldehyde which is a synthetic plastic resin whereas MR resistant ply uses urea-formaldehyde. These synthetic resins impart water-resisting qualities in BWR grade plywood. Moreover, the core layer is treated with various toxicant chemicals that make BWR termite-proof and borer proof.
Boiling water-resistant plywood is the exterior grade plywood and is used for furniture that likely to get wet, kitchen cabinet, lawn chairs, garden tables, etc. BWR plywood is warp free and has excellent bonding, and with zero core gaps.

BWP (Boiling water proof or marine ply)

BWP plywood means Boiling Water Proof Plywood and is popularly known as Marine Grade Plywood. Marine plywood is manufactured out of single species tropical hardwood and jointed using waterproof glue. No voids are left in the core, hence making it a very dense and water-resistant material. Each layer of wood is laid with the grain running at right angles to the next layer and bonded with boiling waterproof synthetic undiluted phenol-formaldehyde adhesive. Marine plywood is also treated with preservatives and a protective finish for external applications. It is a superior grade of plywood which is higher in quality and strength as compared to both MR and BWR plywood. They can be bent and curved without compromising the strength. BWP is the best ply, with the highest resistance to boiling water, and termites, and moisture. But the cost of BWP is also much above the other variants.

Marine plywood is extremely durable and preferred for applications where the plywood has prolonged exposure to water. It is the best choice for marine applications such as woodwork for building ships and boat ad also for manufacturing external garden furniture, kitchen, and bathroom cabinets, etc

Marine ply can be a preferred choice for your kitchen and bathrooms which are more exposed to water and moisture even though they can also be managed by MR or BWR if protected properly.

Conclusion

While selecting a ply wood please be sure about the variety and standard of ply you are going to use.

MR resistant ply is a strong and durable and interior grade ply that can be used for almost every internal application. Avoids using MR resistant ply in areas vulnerable to water and moisture.

BWR ply is boiling water-resistant and exterior grade ply which got very good water-resistant qualities, termite resistant and borer resistant qualities than MR resistant ply. They are preferred for and can be used for external applications, kitchen cabinets, etc with requisite surface finishes.

BWP is the best grade of ply and is a marine grade ply. They are a hundred percent boiling waterproof ply is extensively used for marine applications and kitchen and bathroom cabinets. The cost is comparatively high with respect to MR resistance and BWR ply due to their superior qualities.

Commercial plywood is re-coloured and sold as marine plywood in the local market. Always purchase from a very good brand and obtain Manufacture test certificate.