Where historic buildings are to-be reslated, new slates must always match the existing. However, a decision based on historic precedent may not really be possible because the original quarry is no longer in production. In these cases slates conforming to the recognised standard should stay certain, however with the advent of a European standard, care also be needed to make certain that the chosen slate has a satisfactory life-expectancy. It is important to understand that some slates which contain carbonate can own a long life because the mineral is dispersed within the structure and they are made comparatively thick. Westmorland Green slate tend to be one example. To take account of this, the standard specifies minimum thicknesses about the slate’s performance in each of the sulphur dioxide tests. (ebi is the basic individual thickness to the slates.