BS 1521:1972

This standard BS 1521:1972 Specification for waterproof building papers is classified in these ICS categories:

• 91.100.99 Other construction materials

This British Standard specifies the quality, workmanship, dimensions and performance requirements for two classes of waterproof building papers. Each class is divided into two grades and each grade into two types as follows:

1. Class A. For building purposes, such as for the prevention of draughts or the ingress of water into wall or pitched roof structures but not for damp-proof courses such as are normally required by building byelaws.

   Class A papers are of two grades. They are:

   1. Grade A1, having higher tensile strength and bursting strength test requirements.

   2. Grade A2, having lower tensile strength and bursting strength test requirements.

2. Class B. For temporary purposes, such as for the protection of concrete during curing or as an underlay to concrete to prevent moisture being absorbed by the base.

Class B papers are of two grades. They are:

1. Grade B1, having a higher bursting strength test requirement.

2. Grade B2, having a lower bursting strength test requirement.

All grades are sub-divided into the following types:

Types which are not reinforced with fibres	Types which have fibrous reinforcements
A1	A1F
A2	A2F
B1	B1F
B2	B2F

NOTE The titles of the British Standards referred to in this standard are listed on the inside back cover.

Quality, workmanship, dimensions, performance. Class A for prevention of draughts or ingress of water into wall or pitched roof structures, Class B for temporary purposes such as protection of concrete during curing.