When breathed upon or otherwise rendered moist


Two hundred year old roof, Lake District UK. Lead dowel used to fix slates to battens. It is more usual to find timber dowels or iron nails.


Westmorland slates reclaimed from the roof.

Slates are tested for quality by their thickness, clean smooth cleavage, toughness to allow of holing for nails, and resistance to water. A good slate partially immersed in water should not absorb water to any appreciable extent above the water line…It should also give a clear ring when struck with the knuckles and when breathed upon or otherwise rendered moist, should not emit a clayey odour.

From Architectural Building Construction Vol 2 by Jaggard & Drury, Cambridge University Press 1945

Uncovering a roof photoset

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