Solid wood tends to swell and crack on prolonged exposure to moisture. This is not the case with high quality plywood. Plywood is an engineered wood consisting of layers of veneers bonded together with an adhesive. The veneers are fused together into a single unit by the application of high heat and pressure. When we talk about waterproof plywood, we refer to three grades of plywood; BWR, BWP and Marine. MR or commercial grade plywood also shows some degree of resistance against moisture due to urea formaldehyde resin used in it but is not waterproof in nature.
Marine grade plywood
Marine grade plywood is the best waterproof plywood because it is specifically made for prolonged water exposure. The core and face veneers in marine plywood are obtained only from selected species of wood such as Gurjan, Poplar and Eucalyptus. Concentrated phenolic resin is used to impart waterproofing feature to marine grade plywood waterproof. Marine grade plywood undergoes a water submergence test in which it is placed in water for 72 hours after which it is tested for strength and other properties. The principal use of marine plywood waterproof is in marine applications such as boat and ship building and industrial purposes where water exposure is prolonged.
BWR and BWP grade plywood
Boiling Water Resistant and Boiling Water Proof plywood are the same in terms of quality and waterproofing ability. The adhesive is used in both is phenol formaldehyde which is a synthetic plastic resin. The only difference is that BWP grading is used to indicate blockboard while BWR grade indicates plywood. Hence, BWR grading means waterproof exterior grade plywood while BWP grading means waterproof exterior grade blockboard. BWR and BWP waterproof plywood sheets are also used to make furniture likely to be exposed to moisture frequently. For example, kitchen and bathroom furniture and cabinetry. They are also suitable for external use such as waterproof plywood doors, external cladding, etc.
Ways to waterproof plywood
In case of waterproof grade plywood, the adhesive used
in binding the veneers is able to withstand high moisture without losing its strength.
However, in case of commercial or MR grade plywood, prolonged exposure to moisture damages the veneers of the plywood resulting in the layers disengaging from one another. Thus, waterproofing normal plywood is essential.
The best way to waterproof plywood is to use paint or spray-on waterproof liquid latex. Penetrating oils and sealers can also be used to waterproof plywood. Prior to application of the waterproofing material, the plywood needs to be wiped with a damp cloth. When the surface dries, it needs to be sanded with a 100-200 grit sandpaper to get a very smooth surface for the waterproofing material.
Liquid latex needs to be applied on all the six faces of the plywood including the edges. Liquid latex dries to form a protective plastic layer which protects the plywood against moisture. What you get is a waterproof plywood board.
In case of waterproof paint, brush or roller can be used to coat the plywood. Electric sprayer can also be used to coat the plywood. All the six faces including the edges must be coated with the paint. Cracks and depressions present on the surface are covered by the waterproof paint completely. In case of application of waterproof deck coating for plywood or linseed oil based waterproofing material, a brush or rag is the best choice.
The number of waterproof coating for plywood depends upon the purpose of the plywood. Usually 3 coatings are deemed sufficient for good waterproofing action.
Nowadays, waterproof laminated plywood is also available in the market. Laminate sheet fixed over the plywood protects it against water and scratches besides imparting a decorative appearance.
Prices of waterproof plywood
The waterproof plywood prices are more than the prices of normal plywood sheets. Marine grade plywood cost is more as compared to BWR and BWP grade plywood. This is because the waterproofing ability of marine grade plywood is superior.
In case of BWP grade plywood cost, let’s take the example of 12mm waterproof plywood. The 12mm waterproof plywood price for a standard 8 by 4 feet sheet made of Poplar veneers can be Rs 70/ square feet or more. The price varies according to brand and other additional features of the plywood. We can take another example of BWP grade plywood. A 19mm waterproof plywood sheet of standard size made of Gurjan or Eucalyptus can cost Rs 104/ square feet.
In case of BWR grade plywood cost, let’s take the example of a 6mm waterproof plywood sheet. It can cost Rs 48/ square feet and vary according to brand.
In case of marine grade plywood cost, let’s take the example of 18mm waterproof plywood. A branded marine grade waterproof plywood 18mm can cost Rs 150/ square feet.
Size, quality of wood used, thickness and brand combine to influence the waterproof plywood sheet price. The best brands are the most sought after by customers. Even though the price of waterproof plywood offered by such a brand is expensive, its high quality makes it worth the price.
Apart from retail stores, one can also check the waterproof plywood price list on various online stores. Online stores offer good deals on waterproof plywood and should be checked out.
Waterproof Plywood Price List
Types of Waterproof Plywood
Brown 4 X 8 Feet Waterproof Plywood
Rs 75/ Square Feet
9 Mm Waterproof Plywood For Furniture
Rs 55/ Square Feet
Wooden Plywood Board, Thickness: 4 mm
Rs 60/ Square Feet
6-19 mm , Waterproof Plywood
Rs 55/ Square Feet
Marine Grade Waterproof Glossy Plywood, Thickness: 6 mm