It is at this stage that any adjustments resulting from the sulphur dioxide checks are applied to the basic thickness. Manufacturers must next ensure that no slate will be thinner than this measurement. Considering slates are sold on the basis of nominal thickness; if the range difference are great that nominal thickness will be much bigger than the minimum. If thevariation is small then they will be much nearer. This procedure ensures which slates will be technically satisfactory but there is an alternative route in which it is important for preservation reasons to use denser slates. These may be specified on the basis of traditional construction methods. Obviously it can be unwise to use this alternative to specify thinner slates than required to resist the wind stress.

basic thickness checks