Swithland Slate: Caring for Charnwood’s Historic Roofs

Swithland slate is Leicestershire’s own roofing slate: thick, hand-sawn, light grey-blue when freshly quarried, weathering to purple and leaf-green, and laid in courses that shrink as they climb the roof. Nothing has been quarried in Charnwood Forest for over a century, so every slate on a Swithland roof is irreplaceable stock. That single fact should govern every decision made about one: these roofs are repaired, re-pegged and re-laid rather than stripped, because once the slates leave the site there is no supply to put them back.

Where did Swithland slate come from?

From the eastern flank of Charnwood Forest — the pits in Swithland Wood, the quarries on The Brand estate above Woodhouse Eaves, and the workings at Groby, several now deep, water-filled pools. The stone is the Swithland Formation, a cleaved silty mudrock at least 200 metres thick, and its cleavage is coarse, so it will not split thinly — the property that explains almost everything below.

It has roofed buildings here for a very long time. Roman builders used it in Leicester and at East Bridgford in Nottinghamshire; quarries at Swithland and Groby Park appear in the Borough of Leicester records in 1343; and in 1377–8 work on Leicester Castle consumed 2,000 slates carted from Swithland. Bradgate House, where Lady Jane Grey grew up, was roofed with it. Use on ordinary vernacular buildings spread from about 1750.

Why did the quarries close?

Transport, not exhaustion. Welsh slate is thinner, lighter, far more regular and can be cleaved rather than sawn, covering the same area for a fraction of the weight and labour. Once canals and then railways delivered it into the Midlands in bulk, the local product could not compete on price.

The northern pit in Swithland Wood stopped in 1838, and the Great Pit — reopened with modern machinery in 1859 — ceased production in 1887. At Groby the last slate quarry held on until 1908, when its lessee could no longer compete with the lighter, cheaper Welsh slate the Midland Railway was bringing into Leicestershire.

That is also why Coalville itself has almost none of it: the mining terraces of Hugglescote and Ellistown went up after the railway arrived, roofed in cheap Welsh slate from the start. Swithland survives on what was already standing — older cottages, farm buildings, churches and estate buildings around Swithland, Woodhouse Eaves, Newtown Linford, Quorn and Groby.

How do I recognise a Swithland slate roof?

Feature	Swithland slate	Welsh slate
Thickness	Thick and uneven — around 30 mm (1¼ in) is typical	Thin and consistent, often 5–8 mm
Sizes	Random; scarcely two slates alike	Uniform, ordered by nominal size
Coursing	Diminishing — largest at the eaves, smallest at the ridge	One size across the whole slope
Surface	Sawn by hand, then rubbed smooth with sand and water	Cleanly cleaved and flat
Colour	Grey-blue fresh, weathering purple and leaf-green	Even blue-grey, purple or heather
Fixing	Oak pegs hooked over riven oak laths, bedded in lime	Two nails per slate on sawn battens

Two checks from the pavement usually settle it. Count the slate lengths up one slope: a Welsh roof has one, a Swithland roof a dozen or more, the margins narrowing towards the ridge. Then look along the eaves from the side, where thick slate throws a deep, stepped shadow thin slate never produces.

One detail is often misread. Valleys and hips are rare on pre-nineteenth-century Swithland roofs, and swept or lead-lined valleys are almost always later work — the traditional East Midlands answer is the laced valley, its courses carried through the junction.

Why should a Swithland roof never be casually stripped?

Because the slate cannot be bought new at any price: everything sold as Swithland slate has been reclaimed from a building that lost its roof, so supply is finite and shrinking.

Stripping also destroys the stock: a slate hung on a peg snaps at the peg hole when levered off in a hurry, and one broken at the head cannot be re-hung, so careless removal can waste a large share of a roof’s slates in a day. The covering is often the reason the building is protected at all, so swapping it for concrete tile or thin imported slate is a permanent, visible loss — and on a listed building, a planning matter too.

What are the repair and matching options?

In order of preference:

• Re-pegging and re-laying the existing slates. The slope is stripped by hand, every slate sorted by length, the laths renewed, and the same slates re-hung on new oak pegs to the original gauge, replacing only the broken ones.
• Reclaimed Swithland slate for the shortfall. Specialist yards carry it, and it is the right material — but sort it by thickness and colour first, because reclaimed stock varies far more than one roof’s own slate.
• A sympathetic alternative, where too little survives. Another thick, random-sized natural stone slate laid to diminishing courses reads far better than a thin, uniform one, which can never be reconciled with a Swithland slope’s head laps and margins.

Whatever the route, the gauge has to be right: diminishing courses stay watertight only if the lath spacing reduces evenly as the slates shorten, and a course set too tall over shorter slates loses head lap and leaks. Our slate and pitched roofing is set out to the original coursing, not a standard modern gauge.

Do I need listed building consent?

Very possibly. Replacing the odd slipped slate like for like is maintenance; re-covering a whole slope is not, and changing the covering — material, thickness, colour, texture or coursing — alters the character of the building.

On a listed building, consent is normally required to alter a roof’s covering, shape, height or pitch, and the application will usually need a heritage statement setting out the works and materials. In a conservation area, a change of roofing material can count as an alteration rather than a repair, and permission is often required where the original covering is historically distinctive — Swithland slate certainly is. Speak to your conservation officer before the scaffold is booked.

How should a Swithland roof be looked after?

Nobody should walk on one: the slates crack at the peg hole under a boot, and riven oak laths were never meant for point loads. That is where a drone survey earns its place — close photographs of every course and ridge without a foot on the covering.

Otherwise, keep gutters and valleys clear so water is not backing up beneath the lowest courses, and deal with a slipped slate promptly, because an open slot lets wind under its neighbours and turns one loss into six. Never pressure-wash the slope, and never apply sealant or spray foam underneath: foam bonds to slates and laths alike and turns a repairable roof into a stripped one. Where the structure is sound, targeted repairs are the answer.

Frequently asked questions

Is Swithland slate still quarried?

No. The Great Pit in Swithland Wood closed in 1887 and the last Groby quarry in 1908, and nothing has been quarried in Charnwood Forest since. Every slate sold today is reclaimed from a demolished building, which is why the ones on your roof are worth saving.

How do I tell Swithland slate from Welsh slate?

Thickness and coursing. Swithland slates are thick, with a sawn, slightly rough face, and are laid in diminishing courses — largest at the eaves, smallest at the ridge. Welsh slate is thin, smooth and uniform, one size across the slope, and double-nailed rather than peg-hung on laths.

Can a Swithland slate roof be repaired instead of replaced?

Almost always. The stone outlasts everything holding it up, so the usual work is renewing the laths, pegs and bedding mortar and re-laying the original slates to the same gauge, replacing only the broken ones. A roof shedding slates is rarely worn out — its fixings are.

Do I need listed building consent to re-roof in Swithland slate?

If the building is listed, consent is normally required to alter the roof covering, and a heritage statement is usually expected with the application. Replacing the odd slate like for like is maintenance and does not. In a conservation area a change of material can count as an alteration, so speak to the conservation officer first.

What if there are not enough sound slates left to cover the roof?

Make the shortfall up with reclaimed Swithland slate from a specialist yard, sorted by thickness and colour before laying. Where that is not possible, another thick, random-sized natural stone slate laid to diminishing courses reads far better than thin, uniform slate, whose margins cannot be reconciled with a Swithland slope.

For a free, no-obligation quote on Swithland slate repairs or re-laying in Charnwood and north-west Leicestershire, call Westley on 07366 472857.