Slate Roof. A slate roof always should be laid by a thoroughly competent and reliable man, as any skimping of the work may not be discovered until the roof has served a part of its usefulness.
It is not good practice to lay a slate roof with a rise less than 5" to 1'. The slate should be carefully selected for its color, and a brand used that is known to be tough and non-absorbent. The ordinary wire nail should not be used to fasten the slates, as it will rust off before the roof needs repairing otherwise. A tinned or galvanized nail will give good satisfaction, but upon the best work copper nails should be used, and in all cases they should be driven where there is no danger of a joint coming over them.
In flashing a slate roof, the most durable material is generally the cheapest in the end; therefore copper is the best, though it is used only upon the most expensive work. Tin is used ordinarily and, if well painted before laying, and kept in good condition, it will be satisfactory, though the necessity of climbing over the roof to paint it is often the cause of breaking slates. Sheet lead often is used upon buildings of medium cost.