Slate, clay, or concrete: choosing a tile for a UK roof

The tile on your roof will outlast the boiler, the windows, the kitchen, and probably the car. Get it right and you will not think about it for 30 to 100 years. Get it wrong — wrong pitch, wrong weight, wrong planning context — and you will think about it every time it rains.

Most UK homeowners pick the tile their neighbours have. It feels safe — the row looks matching, the planners don't argue, the roofer says yes. But "what's on the rest of the street" is a weak starting point for a £10,000 decision, because what's on the street is often what was cheapest in 1978. The right covering is a function of five things: the pitch of your roof, the weight your rafters can carry, the planning environment you're in, the lifespan you're paying for, and the budget you actually have.

This piece is for the point where a roofer has said "it needs a re-roof" and you're trying to decide what to put back on. It assumes you've already read the costs guide and have three quotes in front of you that give you options.

The five constraints, in order of bossiness

1. Pitch

The angle of your roof is the first filter. Each covering has a manufacturer-specified minimum pitchbelow which wind-driven rain gets past the laps. Go under it and the roof leaks regardless of how good the installer is — and the manufacturer's warranty voids.

• Natural slate: typically 20°–25° minimum depending on slate size and exposure.
• Clay plain tile: 35°–40° minimum. These are small, narrow, and need a steep pitch.
• Clay pantile: 30°–35° minimum, traditionally laid at 45° in East Anglia and Yorkshire.
• Concrete interlocking tile (Marley Modern, Redland 49, etc.): 17.5°–22.5° minimum, which is why it dominates post-war housing.
• Concrete plain tile: 35° minimum, similar to clay plain.

If your roof is 22° and the neighbours have clay plain tile, you can either change the roof structure (very expensive), accept a concrete interlocking (cheap, wrong heritage look), or live with a slate roof (correct pitch, probably correct heritage look, higher cost). A roofer who quotes you clay plain on a 22° roof is either wrong or selling a leak.

2. Weight

Rafters, purlins, and wall plates were sized for a specific dead load. Putting a heavier covering on old rafters is one of the most common ways to create structural problems after a re-roof.

• Natural slate: 20–30 kg/m² installed. The lightest credible covering.
• Clay plain tile: 55–70 kg/m². Heavy.
• Clay pantile: 45–55 kg/m².
• Concrete interlocking tile: 45–55 kg/m². Similar to clay pantile.
• Concrete plain tile: 65–80 kg/m². Heaviest common covering.

If your house currently has slate and someone quotes you a concrete plain tile re-roof, the covering is nearly three times heavier. The rafters may or may not take it. A good roofer checks the rafter sizing (or asks a structural engineer to) before switching you from a light covering to a heavy one. A bad roofer just quotes the price and leaves the structure for someone else to worry about in ten years.

The safe direction is light → heavy on a new structure (fine) or heavy → light on an old one (fine). The dangerous one is light → heavy on an old one.

3. Planning and heritage

If your property is in any of the following categories, your tile choice is narrowed before you start:

• Listed building (Grade I, II*, II). Listed Building Consent is required for any external change including a re-roof. Expect to be restricted to the original covering material — slate if it was slate, clay if it was clay, often reclaimed rather than new.
• Conservation area. Article 4 directions commonly remove permitted development rights for roofing. Check with your local planning authority before you quote. Typical outcome: natural materials only, matching the existing street.
• World Heritage Site buffer zone (e.g. parts of Bath, Edinburgh, Liverpool, Saltaire). Tighter than an ordinary conservation area. Expect specialist requirements.
• National Park and AONB. Local character policies often restrict tile colour and material, especially on prominent elevations.

These aren't deal-breakers — they're rule-books you have to read first. Ringing your local planning department before you spend money on quotes is a free way to avoid a very expensive surprise.

4. Lifespan

The fair comparison isn't upfront cost. It's cost per year of expected life.

• Natural slate: 80–150 years. Welsh slate at the top end, Spanish and Brazilian at the 80–120 end.
• Clay plain tile: 60–100 years. Hand-made clay can go much further.
• Clay pantile: 60–80 years.
• Concrete interlocking tile: 30–50 years. Older concrete tiles from the 1970s are already failing.
• Concrete plain tile: 40–60 years.

A £12,000 slate roof that lasts 100 years costs £120/year. A £7,000 concrete tile roof that lasts 30 years costs £233/year — nearly twice as much per year of service, before you count the disruption and cost of doing it again. Slate is not a luxury in long-run terms, it's the economical choice for anyone planning to stay more than about 15 years.

5. Budget

In case longevity math isn't persuasive enough: not everyone has £12,000 available, and concrete interlocking tile is a legitimate answer to that constraint. It keeps the rain out, it's compliant with building regs, and it gives you 30 years of dry house for a third less cash up front.

What's nota legitimate answer: a roofer offering to overlay new tiles on top of old ones to save money. That's covered in the costs guide — it usually breaches the rafter loading and it hides whatever is failing underneath.

The options in detail

Welsh slate (premium)

Riven from quarries in Snowdonia. Bangor and Penrhyn are the historic names. Light, fine-grained, almost black when fresh, greying with age. Expected life 100+ years. Most expensive natural slate on the UK market — £5,000–£8,000 of material on a typical 80m² semi. The right answer for a listed or conservation-area property where the original was Welsh.

Spanish and Brazilian slate (mid-premium)

What most UK re-roofs use when "natural slate" is specified without an origin. Good Spanish slate (from Galicia) is excellent value — visually very close to Welsh, 80–120 year lifespan, about 40–60% of the material cost. Cupa and Cupa H12 are among the recognised marks. Brazilian slate covers a wider quality range than Spanish — it runs from excellent to ordinary depending on the quarry and grade — so specify a named importer and a minimum quality classification in the quote rather than leaving "Brazilian slate" as a free-text line item. That is good practice for any imported natural material.

Hand-made clay plain tile

The traditional covering for much of southern England. 265mm × 165mm nominal, tiny individual tiles, heavy when assembled. Hand-made clay (Keymer, Tudor, Aldershaw) is visibly irregular in colour and shape, ages beautifully, and can exceed 150 years. Extremely expensive — clay plain tile roofing is the one case where "more expensive than slate" is common. If your property is in a Kentish or Surrey village and it's a listed building, this is what the planners will want.

Machine-made clay plain tile

Same format as hand-made clay but manufactured with consistent colour and shape. Marley, Sandtoft, Dreadnought. Looks less characterful than hand-made up close, reads similar at street distance, costs 50–70% less. 80–100 year lifespan. The right answer for a southern England semi where the original was clay plain but you're not in a listed situation.

Clay pantile

The S-profile curved tile traditional in East Anglia, East Yorkshire, Lincolnshire, and the Scottish east coast. Modern equivalents from Sandtoft and Marley. Lighter than plain tile, faster to lay, visually distinctive. Same rules as clay plain for lifespan. Don't introduce pantile onto a property in a region that historically used something else — the local character policy will reject it.

Concrete interlocking tile

The dominant UK re-roof covering since about 1970. Marley Modern, Redland 49, Russell Cambrian. Large format, fast to lay, low minimum pitch (17.5° for some profiles), cheap. 30–50 year lifespan. Colour fades noticeably after 15–25 years. Fine for a post-war semi that already has concrete and needs a like-for-like replacement. Wrong answer for anything pre-1940 or any listed/conservation context.

Concrete plain tile

A cost-down substitute for clay plain tile, visually similar at a distance, much heavier. Marley Acme, Redland. 40–60 year lifespan. Rarely the best answer — if clay plain is in budget, use clay; if it isn't, use a concrete interlocking tile instead of trying to fake the look.

Reclaimed slate and tile

Second-hand material recovered from roofs being stripped. Used on listed and conservation work where matching the existing weathered appearance is required. Reclaimed Welsh slate is the most common — expensive, scarce, but often the only way to get Listed Building Consent. Expect a surcharge of 50–100% over equivalent new material and longer lead times from specialist merchants.

How to have the conversation with your roofer

A useful script:

"Can you quote me for two options? Option A is a like-for-like replacement in [the current material]. Option B is an upgrade to [natural slate / hand-made clay / whatever the level-up is]. I'd like to see both quotes itemised so I can compare cost per year of life, and I'd like you to confirm the rafters will carry the covering you're quoting."

A decent roofer will give you both without pushback. If they refuse option B because "we don't do slate", that's an honest answer and you want another quote from a roofer who does. If they refuse option B because it would undercut their margin on A, you'll hear it in the reasons they give.

After you've decided

Use the hiring checklist to sanity-check each roofer. Use the costs guide to sanity-check the numbers. If you want three quotes from roofers who cover your postcode, the quote form will do that. The brief goes out with the tile and material preferences you pick, so you get comparable quotes for what you actually want — not the cheapest interlocking tile the roofer had in the van.