The following is a glossary of terms used within this website, and also in general use in the trade when discussing Collyweston roofing. We hope it may be of use to you!
Backer
narrow slates laid roughly centrally over a wide slate to accommodate the increasing number of slates in each course as work progresses up the roof
Batten
sawn wooden support for hanging or nailing stone slates.
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
Clive
to split the Collyweston log into thin sheets for dressing to make slates
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.
Dressing
the process of shaping the stone slate and producing the edge detail using either a chisel-edged hammer or a bladed tool.
Eaves
of stone slates: the short course laid at the eaves under the first full course. Also referred to as the under-eaves. With the shortage of Collyweston slate, the use of blue slate has become quite widespread
Fissile
rock which can be split along
bedding planes
Flashing
pieces of lead sheet used to waterproof joints with abutments, i.e. walls, other types of roof covering, etc.
Flaunching
a fillet of lime mortar laid over the roof covering and soakers to joint the roof covering to an abutment.
Fixings
nails or pegs
Gallet
small pieces of stone slate or metamorphic slate bedded in lime mortar at the head of a slate to support the slate above.
Gauge
the spacing of
laths or battens up the roof slope. In stone slating, the gauge is always variable
Head
the top edge of a stone slate as laid.
Head lap
in double lap slating (the normal method), the amount by which a stone slate overlaps the stone slate in the course next but one below.
Lime Mortar
mortar made up from a mixture of sharp sand and lime putty, usually in the proportions of 3 parts sand to 1 part lime putty.
Lath
split wooden support for hanging stone slates.
Log
colloquial term used to refer to the fissile stone "lumps" from which slate is clived after frosting
Margin
strictly the area, but more commonly the length, of the exposed part of the slate .
Overburden
in quarrying: useless material which overlies a bed of useful material.
Pendle
generally a quarrying term for any fissile rock.
Pig
a course with a larger margin than the course(s) below resulting from poor setting out and a failure to maintain adequate
head lap.
Pitch
the angle of the rafters to the horizontal. The pitch of the stone slates will be significantly less because they are resting on each other, but this is taken into account by the traditional rafter pitch and lap relationship for the slate and the locality.
Pointing
use of mortar to fill the vertical joints and to seal the
tail gap of stone slating. Pointing may show (undesirable) or be raked or held back. Often associated with bedding.
Presents
stone slates formed by natural weathering in near surface deposits. They are often thicker than hand-split stone slates produced from deeper layers.
Random
(of stone slate): variable length and width.
(of roofing): slates laid with reducing length up the roof slope and the widths selected and placed so that they provide at least the minimum
side lap over the slates in the course below.
Regularly
(of
diminishing or random slating): the system whereby each successive margin is the same size or smaller than those below. It does not mean that there are an equal number of courses of each margin size.
Ridge
The tiles that cover the top of a roof where 2 slopes come together. Mostly formed using white hogs-back tiles, but can be of sawn limestone and other clay materials.
Sedimentary
rocks which have been formed from other rocks which have been broken down by weathering, or rocks formed by biological or chemical actions. If they can be split to make roofing (
metamorphic slate bedded in lime mortar at the head of a slate to support the slate above. Synonym: gallet.
Shoulder
to remove the top corners of a stone slate; the top corners of stone slates. Excessive shouldering can result in a leaking roof.
Side lap
the amount by which a stone slate laterally overlaps the stone slate in the course below.
Soaker
lead pieces cut to the length of the gauge plus the head/tail lap and folded into an L shaped section, fitted against an abutment, such as a wall. It is usual in Collyweston roofing to cover the joint with a lime mortar flaunching. It is good practice to paint the lead with a minimum of 2 coats of bitumastic paint before using, to prevent adverse reaction between the lime and lead.
Slate
in this web-site, reference is made to Collyweston slate. Since Collyweston slate is limestone, it isn't truly a slate, not being metamorphic in origin.
Sprocket
a small piece of timber fixed to the foot of a rafter to give the roof covering a tilt.
Tacks
small strips of lead nailed to the battens or laths and folded up at the bottom edge to restrain a slate in place, normally used when replacing a slate that cannot be nailed in the conventional manner. Aesthetically tacks made from heavy gauge copper wire are less obtrusive and less prone to damage from snow slip and the weather.
Tail
the bottom edge of a stone slate as laid.
Tilt
the lift provided to the eaves course to ensure that successive courses lie correctly without gaps at the
tail. On the main areas of the roof slope, the tail of each stone slate rests on two thicknesses of stone slate in the course next but one below. At the eaves, the first full course rests on only one thickness - the eaves slate. Essentially, the tilt replaces the missing thickness.
Torching
Haired lime mortar applied to the underside of stone slates to render them wind proof.
half torching or single torching
: application of haired lime mortar between the top edge of the lath or batten and the underside of the slates.
full torching
: application of haired lime mortar between the top and bottom edges of the laths or battens and the underside of the slates.
Unweathered
of stone roofing: rock which is too deep to have been subjected to
weathering and consequently has to be split by mechanical action or frosting after extraction.
Underslating Felt or Underlay
a sheet material laid over the rafters to prevent wind blown rain and snow from entering the roof space. This job was previously carried out by the use of torching
.
Weathering
the process by which rocks are broken down and decomposed by the action of external agencies such as wind, rain, temperature changes, plants and bacteria.
