1 Scope 1.1
This Standard covers three types of asphalt-coated glass-base sheets (asphalt-impregnated and -coated glass-roll roofing) surfaced with insoluble inorganic mineral matter:
(a) Type I: a lightweight base sheet intended primarily for use as an underlayment for shingles.
(b) Type II: a standard-weight roofing base sheet intended for use as the first ply in a roofing membrane over insulation.
(c) Type III: a venting base sheet surfaced with fine mineral matter on top and mineral granules on the bottom. This type is used in built-up roofing systems as a first ply to relieve pressure through lateral vapour movement.
Type III felt can be unperforated or, if used for spot mopping, contain perforations of a size specified in Table 1. 1.2
In CSA Standards, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; "should" is used to express a recommendation or that which is advised but not required; and "may" is used to express an option or that which is permissible within the limits of the standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Legends to equations and figures are considered requirements. 1.3
The values given in SI (metric) units are the standard. The values given in parentheses are for information only.