Building Materials, Third Edition

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These boards built up of felting from wood or vegetable (wood wastes, waste paper, agricultural
wastes, etc.) are classified by the process of their moulding. If the boards are moulded by wet
process, the main bond is by the felting of woody fibres and not by added glue. For the boards
moulded by dry process, the bond between the predried fibres is improved by adding 4–8% of
synthetic resin. For better performance wood preservatives and other admixtures are often
added to the pulp. Insulating boards are not compressed during manufacture. Fibre boards are
manufactured in various densities like soft, medium and hard. The soft boards are used for
walls and ceilings. Medium boards find their application in panelling, partition walls, doors
and windows. Hard boards have one surface smooth and the other one textured. These have
higher densities, better mechnical properties, and improved moisture and termite resistances.
The strength and weather properties of hard boards can be improved by oil tempertering and
such boards are known as tempered hard boards. Some of the trade names of hard boards are
Masonite. Celotex. Essex boards, etc.

g—™— Hard boards are classified as medium, standard or normal and tempered hard
boards depending upon the density. The requirements of hard boards are given in Tables 4.7,
4.8 and 4.9.

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