Cotswold Stone Slate Roofing

Cotswold stone slate roofing is one of the few regional roofing traditions in England that never died out. Cotswold District Council's technical guidance describes it as second in importance, as a building material, only to Cotswold stone walling, and records it surviving from Chipping Campden in the north to near Bath in the south. This guide covers what the material is, why the courses diminish, how the roofs are fixed, and what changes when a building is listed.

None of the three names is quite right, which is why all three are used. It is not a metamorphic slate like Welsh slate, and it is not a tile in the sense of a moulded object. Cotswold District Council notes that stone tile tends to be used in the south of the district and stone slate in the north; older sources use tile-stone.

Historic England draws the same distinction. Its technical advice note on stone slate roofing covers stone slates made from sedimentary rocks — mainly limestone and sandstone — rather than real slates, which come from metamorphic rock, and notes that they split along bedding planes rather than cleavage planes.

So Cotswold stone slates, Cotswold roof slates, Cotswold slates, Cotswold stone tiles and tile-stone all describe the same thing: sedimentary limestone split thin along its bedding planes and hung in courses.

Cotswold stone slates are made from two oolitic limestones, worked in completely different ways.

Presents

Forest Marble is quarried near the surface and split by hand shortly after extraction, while the stone still holds its natural moisture — its "quarry sap". Slates made this way are called presents. It is the older method, probably dating from the Roman period.

Pendle

Stonesfield Slate is frost-split. The stone was mined in rough block form, called pendle, brought to the surface and laid out in fields to frost. As the frost opened the natural bedding planes, slaters worked to assist the split. The result was thinner and more regular than presents, and was prized for the most prestigious roofs, including those of the Oxford colleges.

A fissile sedimentary rock cannot be supplied in consistent sizes the way Welsh slate can. The stone yields far more small slates than large ones, and the Cotswold tradition made that constraint the roof's defining feature. Historic England describes stone slates as randomly sized and laid in diminishing courses.

The largest slates go at the eaves in a double course, where they throw water clear of the wall. Cotswold District Council records these as normally around 600 mm long, some up to 750 mm, and gives their name as cussoms, with the course above them called followers. The smallest slates are the most plentiful and go highest up the slope; at around 150 mm long they are known as short cocks. Between the two the courses step down steadily, which is what gives a Cotswold roof its banded, narrowing appearance.

That is also why a stone roof is set out to a schedule. Every course has a size, and the sizes are planned across the slope before the first slate is laid.

Cotswold roofs are usually simple in form — a straight pitch, which the council's guidance gives as typically 47° to 55°, spanning two gable ends. Where a roof turns through 90° on plan, the tradition produced the swept valley. Historic England's guidance names the swept valleys of the Cotswolds specifically, noting that the curve is formed where roof planes intersect on the steeper pitches that small, thin slates require.

Specially cut slates form a gentle curve through the valley. In the tighter patterns, courses of two slates across the valley alternate with three; where there are three, the central wedge-shaped slate needs no peg and is held by the slates either side. The wedge is called a bottomer and its neighbours lie-byes or side skews, with the next course turning the valley on two skews.

Modern work often substitutes a close-mitred or open lead valley. Both are cheaper to construct. The council's guidance is that neither appears as satisfactory as the traditional valley, and that both are best avoided.

Each slate is hung on one, or sometimes two, wooden pegs driven through a hole near its head. Traditionally the slater found a thin point in the slate and broke through it with a pointed hammer to form an hour-glass shaped hole; today it is drilled. Pegs were usually cleft oak, driven until firm, with the slate hung over the batten. Ridges were made from a simple angled section of dressed stone, and on more elaborate buildings, mostly churches, a roll-topped stone ridge was used.

Cotswold District Council's guidance gives the weight of a traditional stone slate roof as about 1000 kg per 10 m² — around 100 kg/m². That weight often produces a slight bend in the roof, and the guidance notes it is now thought roofs were built to allow for it: the bow packs the slates more closely together and sheds rain and snow more effectively.

Well maintained, a very long time. The council's guidance is that with regular maintenance a Cotswold roof can easily last 100 years and could last 200 or 300, and that many roofs being replaced on the oldest Cotswold buildings are thought to be original.

The main agent of decay is frost. The traditional maintenance task was scraping the roof free of moisture-holding moss, now largely discontinued on grounds of cost — which the guidance calls a false economy, noting that a roof scraped once a year could last twice as long. A common finding at replacement is that around half the slates have perished.

This is where stone roofing stops being a material choice and becomes a consent matter.

The current development plan for the area is the Cotswold District Local Plan 2011-2031, adopted on 3 August 2018. Designated heritage assets are dealt with under Policy EN10 and conservation areas under Policy EN11, and the plan identifies natural stone roof tiles, alongside Cotswold building stone and dry-stone walls, as one of the local materials that define the district's built character. Policy wording changes over time, so check the current plan and speak to the conservation officer rather than relying on a summary.

Historic England's technical advice note on stone slate roofing is the standard reference for repair and reroofing in England. Because material and method vary from region to region it deals in general principles and directs specifiers to the local planning authority for regional practice — which for the Cotswolds means Cotswold District Council. On repair it is explicit that damaged slates should be redressed with hand tools rather than sawn.

Cotsway is ethically sourced natural stone supplied in 41 sizes for random diminishing courses, in Aged and Buff. It suits new build, extensions, barn conversions and unlisted properties within Conservation Areas — roofs that need to read as Cotswold without being subject to listed building consent.

On a listed building the position is different and the guidance above governs it. Speak to your conservation officer first; approval is property-specific and must be obtained for every project.

Cotsway weighs 120-140 kg/m², so the structure needs checking on any roof not already carrying stone.

Last reviewed August 2026. Planning policy changes — check the current Local Plan and speak to your conservation officer before relying on any summary.