What are the traditional names for Cotswold stone slates?

Owners are often puzzled to find a surveyor writing "stone tiles" while the builder next door says "stone slates". They are talking about the same covering. Cotswold District Council's technical guidance observes that southern parts of the area favour "stone tile" while the northern parts favour "stone slate". That is local habit, not two different products.

It still pays to notice which word a document uses. Planning papers, conservation appraisals, insurance schedules and builders' quotes are each written by different people, and they do not all choose the same term. If a quote says "stone tiles" and your listing description says "stone slates", the two are consistent. If one of them says "Cotswold-style" or "reconstituted", they may not be, and that deserves a question.

A third word sometimes appears: "slate" on its own. Welsh and Spanish slate are entirely different materials, so a loose use of the word on a quote is worth clearing up before any work is agreed.

Quarried stone gives a great many small slates but few large ones. The roof is therefore laid in diminishing courses, big pieces near the gutter and small ones near the ridge, and each size carries a name.

The largest slates, normally about 600 mm long but sometimes up to 750 mm, form a doubled row along the eaves. These are the cussoms. Above them come the followers, and the sizes then step down course by course. The smallest, called short cocks, crown the upper slope and were only 150 mm long.

Those names come straight from the council's guidance, and they are still used by slaters who work in stone. If you hear them on site, the person is describing a slate by its job. A cussom is not a type of stone; it is any slate of the right size laid in that eaves position.

Our separate page on diminishing courses covers the pattern in full.

Valleys have a vocabulary of their own. A traditional swept valley uses purpose-cut slates that curve gently round the internal corner, so no lead channel shows. The guidance names the pieces involved: the bottomer at the base, lie-byes (also called side skews) and skews.

You will seldom need to use those words yourself, but they can show up in a specification or an old building report, and it helps to know they are slates rather than lead details. The council's guidance adds that close-mitred and open lead valleys cost less to build, yet neither looks as satisfactory as the traditional version, so it advises steering clear of them.

Ridges follow the same logic. Each one was shaped from a block of dressed stone into a simple angle, never bought as a factory fitting, which is why we describe them on their own page rather than as an accessory.

When someone prices a stone roof from a few photographs, the wording they choose is the first sign of how well they know the material. A quote that talks of "stone slates, hand-dressed and pegged" describes a method. One that says only "roof tiles" does not, and the gap can be large.

The same goes for paperwork. Your home insurance may describe the roof covering in a particular way, and the description should match what is on the building. If you are unsure, check the wording with your insurer before work begins, because we do not handle claims or promise outcomes.

Conservation officers read these words too. In a conservation area the covering helps define how the street looks, and our page on stone roofs in conservation areas explains how that can affect what you are allowed to do.

A few pairs of words cause trouble. Pitch, for example, is the angle of the slope, and the council's guidance describes a traditional stone roof as a simple straight pitch of 47 to 55 degrees. That is how steep these roofs usually were, not a legal minimum. Our page on stone roof pitch keeps the two ideas apart.

Gauge and lap are another pair. The gauge is the visible stretch of each slate, while the lap is the amount that is hidden under the course above. People say "overlap" for both, and a quote that mentions either needs to be read with care.

Then there is the word "repair". In a stone roof it can mean replacing a handful of slates, rehanging a section or stripping and relaying a slope, and these are very different jobs. Our page on stone slate repairs shows where the line between them sits.

You should never need a glossary to understand your own roof. When we survey, we describe what we find in ordinary terms, name the stone slates by position only where it helps, and put the findings next to photographs taken on your own roof. The written quote follows.

If a document leaves you unsure, send it to us along with a couple of pictures. We will translate it and tell you which parts, if any, call for action. A short list of the terms in your paperwork, set beside what each one means on your roof, is often the most useful thing we can write down. Our wider Cotswold stone roofing page lists the other topics we cover.