There are different varieties of plywood available in the market, when buying plywoods in Chennai one needs to be aware on which grade and brand of plywood is required.
Consider the above case of MR vs. BWR grade. People often think Moisture Resistant means waterproof. However this is not the case.
Please note that MR (Moisture resistant) is of a lesser quality and cost compared to BWR grade. While it true that MR plywood can resist a certain degree of moisture and humidity, it certainly cannot be called waterproof. On the other hand, BWR plywood is a waterproof plywood.
MR is an interior grade plywood useful for making indoor furniture (office furniture, furniture where there is less application of water or moisture) while BWR plywood is exterior grade(places like kitchen, bathroom doors, furniture below water tanks or any spot where the surface is directly exposed to sunlight and water .
BWR – Phenol formaldehyde synthetic is used for glueing the plies together. This is a synthetic plastic resin.
MR – Urea formaldehyde resin is used for bonding the plies to each other. UF resin is not considered to be very eco-friendly.
PS: Some shopkeepers erroneously (or is it deliberately?) inform customers that Marine plywood is the same as BWR grade waterproof plywood. This is simply not the case. Marine plywood is a much better kind of plywood in which unextended (undiluted) phenolic resins are used for glueing the plies together, which makes it stronger. Marine ply is meant for extreme cases of exterior use, such as for making boats and ships or other river equipment, where the plywood is sure to become and remain wet for a prolonged duration.