Glossary of Stone Roofing Terminology

Bedding(of rocks): a plane parallel to the surface of deposition of a rock. The plane along which stone slates often, but not invariably split

(of slating): use of mortar in spots or fillets to prevent stone slates from rocking. In some areas, it is used to improve weather tightness

Breeze:A mixture of clinker and lime or cement. When used to bed slates it could be crushed down to fill any gaps without excessive separation of the slates.

Cleavage: Slate cleavage is developed in fine grained rocks following metamorphism. Under the influence of pressure and heat the pre-existing slatey minerals are partially recrystallised and aligned perpendicular to the pressure. Slates cleave parallel to the platey minerals a roofing system using "diamond" shaped pieces of stone hung from one corner. The shape is actually hexagonal to avoid three layers where adjacent slates and courses meet. An ancient method found on many Roman sites and in Dumfries.

Clive:To clive is to set a log cracked by frost on edge and gently tap with a special hammer, turning to each edge until splitting is completed.

Diminishing:The system whereby slates are sorted by length and laid with the longest at the eaves, diminishing to the smallest at the ridge. It is essential that the minimum head lap is maintained when there is a change of slate length between two courses. This also ensures that each successive margin is the same size or smaller than those below.

Double Lap:Stone slates laid so that each course overlaps the course next but one below. In some regions and in some special applications, triple lap slating (where each course overlaps the course next but two below) is adopted.

Dressing:The process of shaping the stone slate and producing the edge detail using either a chisel-edged hammer or a bladed tool. Regional differences exist for the edge detail which may be square or beveled. Synonyms: trimming, fettling (Yorks, Lancs)

Heap:A quantity of dressed slates of all sizes on the ground as follows:-

Case: =3No. Slates

Hundred:=40 Cases i.e. 120 Slates

Heap:=7 hundreds i.e. 840 Slates plus 13 large ones.

Log:A lump of stone of no defined size quarried for the purpose of making slates.

Pied:A method of burying logs during the summer to prevent drying out.

Pit:A mine or quarry for the extraction of stone for slating.

Sprocket:The additional pieces of rafter fixed to the main rafter to give the tilt at the eaves.

Square:One hundred square feet of slating laid on the roof. A "heap" should produce about two squares of slating laid on the roof.

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