Eternite Thrutone Slates This is a block of seven house completed in Croydon Surrey for a developer .The roof covering was Eternite Thrutone Artificial slates on Tyvek felt, and seven large Code 6 and code 7 sheet milled lead dormers. Picture 1 This picture shows the seven properties front side on. Picture 2 This picture shows the rear of the rear of the seven properties.. Picture 3 This picture shows the detail of the front roof pitch. Picture 4 This picture shows the detail to the rear of the roof showing lead dormers.