It is at this stage which any adjustments resulting from the sulphur dioxide examinations are applied to the basic thickness. Manufacturers must then ensure that no slate is thinner than this value. Considering slates are sold on the basis of nominal thickness; if the range variation is large the moderate thickness will be much larger than the minimum. If thevariation looks smaller then they will become much nearer. This process ensures your slates will be technically satisfactory but there is an alternative route where it is important for preservation reasons to use thicker slates. These can be specified on the basis of traditional construction methods. Obviously it would be unwise to use this alternative to specify thinner slates than required to resist the wind loads.