Work on the wood sense

Jagvir Goyal

Among many materials purchased by the house builder during the construction of his house, plywood occupies a prominent position.Wood being a costly and heavy item, can’t be used in every wooden item. Plywood thus finds use in the door panels, cupboards, kitchen cabinets, bathroom vanities, LCD display units, crockery almirahs, walk-in closets and wooden shelfs. A long list of plywood boards of different thicknesses is handed over by the carpenter at the beginning of woodwork. Performance of wood items is significantly dependent on the quality of plywood used in them. Plywood should,  therefore, be purchased carefully after examining its important qualities. Let's have a look at them:

IS codes

Each type of plywood has different quality and is used for a specific purpose and thus has been assigned different IS code that specifies the requirements to meet the quality parameters. Commercial plywood and flexible plywood are given IS 303 mark and to know the difference between the two, further parameters are to be checked. Marine plywood has to bear IS 710 mark. Shuttering plywood should conform to IS 4990 mark. It is used in shuttering work. Structural plywood is marked with IS 10701 mark. It is used in beams, silos and in structural components. Fire-retardant plywood should bear IS 5509 mark. In houses, flexible plywood bearing IS 303 and marine plywood bearing IS 710 is used.

Check quality mark

While buying plywood, check the IS mark on each board of plywood. If you are buying flexible plywood, it should carry IS 303 mark as explained above. If you are buying marine plywood, it should bear IS 710 mark. Marine plywood is much better and costlier than flexible plywood. As the name suggests, it is mostly used in situations where it is exposed to water. It is used even in making boats. In houses, it can be used for exterior surfaces otherwise particular grades of flexible plywood are good enough for exterior use in houses.

Be careful about the grade

Plywood has three grades. These are: BWP grade, BWR grade and MR grade. BWP grade means Boiling Water Proof grade. BWR means Boiling Water Resistant grade. MR grade means Moisture Resistant grade. Among these, BWP grade plywood is best of the three and MR grade is of inferior quality. While buying plywood, ensure that it is of BWP grade. If you want to save money then BWP grade plywood can be used for exterior door panels and for kitchen cabinets and bathroom vanities while BWR grade plywood can be used for cupboards, LED panels and other such purposes. Avoid using MR grade plywood.

Exterior/interior grade

In common language, the words exterior and interior grade are used. These grades are no different from BWP, BWR and MR grades. BWP grade plywood is called exterior grade plywood while BWR grade and MR grade plywoods are called interior grade plywoods. MR grade plywood is also known as commercial plywood. Some architects and dealers term BWP and BWR grade plywood as Marine plywood which is incorrect. 

The quality of resin

The resin used in manufacture of plywood plays a very important role in maintaining the indoor air quality of your house. Volatile Organic Compounds (VOCs) emitted from poor-quality resins can pose health hazards. The resin or adhesive used in manufacture of plywood is either phenolic or amino-plastic type, both being hot pressed synthetic resins conforming to IS 848. In both types of resins, formaldehyde is used. In phenolic resin, phenol or synthetic polymer and formaldehyde are mixed while in amino-plastic resin, urea and formaldehyde are mixed. Among these two, phenolic formaldehyde resin is better and should be chosen. However, focus today is on using formaldehyde-free resins for manufacture of plywood as formaldehyde is not eco-friendly. Therefore look for a brand that claims to provide formaldehyde free and eco-friendly plywoods. 

Thickness matters

Plywood is produced in different thicknesses. These are 3 mm, 4 mm, 6 mm, 9 mm, 12 mm, 16 mm, 19 mm and 25 mm. In houses, mostly, 19 mm, 12 mm and 6 mm plywood is used.  While buying plywood, thickness should be checked carefully as difference is in millimetres only and sometimes, lesser thickness plywood gets supplied. Good manufacturers mention the thickness on the plywood surface also. 

Is it different?

Ply boards or simply boards are commonly used words in construction industry but in fact, there is no such word like ply board. Users and suppliers have divided the plywood into two categories for their own convenience. Thin sheets of plywood like 3mm, 4 mm are termed as plywood while thicker sheets of 12 mm, 19 mm are termed as ply boards. Any confusion on this account should be avoided.

— The writer is former HoD and Engineer-in-Chief, Civil Engineering Department in a Punjab PSU