Sustainability is one of the guiding principles behind everything Popular Wood Crafts manufactures. Plywood being a wood based product recognizes the potential of wood as a truly renewable and sustainable building material.
What makes building with plywood sustainable?
The answer lies majorly in plywood’s low embodied energy – which essentially means that minimal non-renewable energy is consumed in the production of and construction with plywood. Wood also has inherent thermal properties, meaning plywood structures rely much less on carbon-emitting heating or cooling appliances. Plywood also has natural durability, with many Indian hardwoods (ex- Eucalyptus) boasting an above ground life of 25+ years, which essentially can be interpreted as less energy consumed in maintenance, demolition and new construction. Apart from all of the above, add to it the major characteristic of Wood’s recyclability and the fact that wood stores carbon for life. Trees absorb a large portion of carbon dioxide from the environment and the carbon is directly stored in the form of wood thus reducing free carbon in the environment. More we grow and harvest trees to be used as wood, more carbon we can manage to eliminate from the atmosphere.

The durability of plywood depends majorly on the bonding quality used in manufacturing which depends on the resin (glue) used while stacking up wood veneers on top of each other. Plywood in general is manufactured using two primary adhesives. The exterior grade marine ply is manufactured using a phenolic based formaldehyde resin while the interior grades are generally manufactured with Melamine fortified Urea formaldehyde resin.

Structural plywood is manufactured from a variety of hardwood and softwood species, which may not be durable in exposed weather situations, and therefore must be preservative treated to ensure its full service life can be reached.

In India, plywood is available in several dimensions but a few standard sizes are as follows :

Length : 2440 mm (8 ft), 2135 mm (7 ft), 1830 mm (6 ft)
Width : 1220 mm. (4ft), 915 mm (3ft)
Thickness : Standard plywood panels are available in 4, 6, 9, 12, 16, 18, 19, 25 (mm) thicknesses.

Structural plywood – Structural grade plywood is suitable for use in all permanent structural applications. It is generally manufactured from hardwood timber species and is used for a range of structural applications including formworks, flooring, bracing and manufactured beams.

Interior plywood – These are plywood used in non-structural interior applications which are generally not subject to high load, but where an aesthetic finish is priority. Its applications include furniture construction such as cabinets, tables, shelves, internal wall paneling, furniture, ceiling linings and interior door skins. Interior Grade of plywood is generally referred to as MR Grade or Commercial Grade in the Indian Market Space. It meets the specifications of IS – 303.

Exterior plywood – Exterior grade of plywood is intended for use in exterior applications subject to the elements occasionally, where a high quality aesthetic finish is also required. Exterior Grade plywood in India generally refers to Marine Ply. Applications include outdoor furniture, flooring, exterior door skins, hoarding, signs and non-structural cladding.

Marine plywood – Marine Ply is a subset of Exterior grade plywood. Its a structural plywood intended for hulls of boats and yachts and other furniture applications such as in washrooms, kitchens or outside furniture meant to withstand the elements specifically water. It is also used in aircraft construction. Marine plywood is manufactured to minimize water penetration, and uses Phenolic bonded formaldehyde adhesive bond.

Plywood is primarily manufactured using two types of gluelines :

• Type A – Phenol Formaldehyde Resin
• Type B – Melamine – Urea Formaldehyde Resin

Type A Bond – Phenol Formaldehyde bond is a permanent bond required for all structural and marine plywoods. The Phenolic bonded resin is recognisable by its black colour, which is made to not deteriorate under wet conditions, heat or cold.

Type B Bond – Recognisable by its light glueline colour, Melamine Fortified Urea Formaldehyde is appropriate for interior applications, specially in tropical areas marked by high humidity free from wet or damp conditions.

Plywood are treated by a range of preservatives depending on the application. Most widely used preservatives include CCA (copper chrome arsenate) , LOSPs (light organic solvent preservatives) and for veneers, Ruply and ACQ (Alkaline Copper Quaternary Compounds).

For residential or commercial construction purposes, the most suitable treatments are Copper Chromium Arsenate (CCA) and Light Organic Solvent Preservative (LOSP).

Plywood needs to be properly handled, stored and protected from the elements as much as possible to extend its service life:

• The storage area in particular should be protected from the sun & rain that could cause any rapid changes in temperature & humidity. To avoid staining & surface checking, the plywood sheets should not be exposed to the weather while awaiting usage.
• During storage, support for the panel sheets should be provided at both ends along with support at 600mm wide intermediate centres to avoid distortion of ply.
• The plywood stacks should be stacked flat on its face and not on its edge. Additionally the stack should be kept in dry conditions and clear of ground contact to avoid Termite Infestation.

Plywood, if mishandled, may get subjected to decay or termite attack. Specifically, in-ground applications run a high risk of causing both decay conditions and termite attack. For plywood sheets which are permanently exposed to the weather, its essential to treat it with the necessary preservatives against fungal attack (rot), either painted or unpainted. Termite Infestation is not a problem for plywood when used in above ground applications.

Plywood can be treated through either Veneer Impregnation, prior to pressing OR Preservative treatment after manufacture(Envelope Treatment).

Lastly, but most importantly, Plywood is originally made from wood and therefore is susceptible to respond to elements as wood does. We highly recommend avoiding water contact with plywood at all times to protect against any adhesive breakdown, wood swelling or bending responses. Unless a plywood is of Marine Grade (IS – 710), it is susceptible to react negatively on contact with water.

Regular plywood sheets can be cut, sawn, and drilled using any ordinary carpenter’s tools or woodworking tools.

The placement of screwholes or nailing in particular plywood elements should be restricted in size and location in order to maintain the structural integrity of the plywood panel. A minimum of 3 inch gap should be provided between two holes or between the screw hole and the edge.

Since Plywood is based on timber, it has the same practical workability attributes as solid structural timber with the added advantage of its flexibility. Bending or moulding plywood is relatively easy. Manufactured plywood panels are generally very stable, however occasionally, warping, bowing or twisting can occur due to unsupervised handling such as moisture imbalances, unbalanced laminates, paint coats or unbalanced stresses.

Exposed surfaces of plywood must be surface finished to prevent surface checking or cracking. These problems generally occur due to absorption or loss of moisture through the face veneer. On the other hand, structural plywood used internally does not necessarily require a surface finish.

Exterior Plywood
Exterior Grade Plywood used for exterior applications may be finished by either of the following ways :

• Painting
• Coating with water repellents
• Overlaying with medium density phenolic impregnated papers.

Please Note: While not necessary, it is advised to edge seal plywood post any cuts or sawing as it minimizes moisture uptake. For best paint performance, use 100% acrylic latex paint systems on plywood. Oil based or alkyd enamel paint systems are not recommended for usage in weather-exposed applications of plywood.

Interior Plywood
In the case of Interior Grade Plywood, Clear finishing, French polishing, staining and painting of plywood are all viable options. [Paint manufacturer’s directions are strictly advised.]

Before initiating any finish work please ensure that the plywood is dry (below 12 – 15% moisture content) and that the surface of the ply panel to be painted is clean, smooth and wax free. We recommend stain or matt finishes and paint finishes on interior grade plywood as they lend a high quality aesthetically pleasing surface which are more uniform with a timber’s characteristics. We advise against using high gloss finishes and paints as they would highlight beat marks from sanding, knots, grain variations, patches or even open defects.