Ask three suppliers for natural slate and you may be offered three origins: Welsh, Spanish and Brazilian. All are real stone split from the ground, and all can keep rain out for decades. They are not interchangeable, though. They differ in colour and surface, in the thickness of each slate, in the lifespans claimed for them and, most visibly, in price per square metre. A fourth consideration, which only an old building raises, is whether the council will accept the choice at all.
This guide compares the sources side by side. It sets the published national figures for each source side by side. Brazilian slate varies so much by quarry and product that its life and cost are best judged on the supplier's test certificates and the written quote. If you want a verdict on the quality of one source alone, our page on Spanish slate quality goes deeper. The main service page is slate roofing in Stroud, and for the wider case for and against slate, see slate roof advantages and drawbacks.
Three origins, one family of stone
Slate is a fine-grained metamorphic rock that splits along natural planes into thin sheets. Roofing slate is quarried or mined, split by hand or machine, trimmed to size and graded. Welsh slate comes from quarries in north Wales. Spanish slate is mostly imported from quarries in north-west Spain, and Brazilian slate arrives from the other side of the Atlantic. Each place has its own rock, so the finished slate carries different mineral content, a different grain and a different feel under the hand.
That variation is the reason a roofer asks for the origin on the order and on the quote. Two slates described only as natural slate may differ in thickness, tolerance and in how they weather. A roof laid with a mix of origins can also age unevenly, with some slopes changing colour while others hold theirs.
What the origin does not decide
Origin does not tell you the quality of one batch. Grades differ within every source, and individual quarries differ again. A good Spanish slate can outperform a poor Welsh one, and the reverse is also true. What matters is the test evidence for the particular product, the thickness and the way it is fixed. That is why the sections below treat origin as a starting point for questions, not a verdict.
Look, colour and how each weathers
Appearance is the most personal difference and the one sourced figures cannot settle. In general terms, Welsh slate is associated with blue-grey and purple-grey tones and a slightly textured, riven surface. Spanish slate is usually a more uniform dark grey that suits a clean, even finish. Brazilian slate can vary more in tone within a batch. These are descriptions of typical appearance, not rules, and every quarry and grade differs.
Ask for a sample, then wet it
A slate looks different dry and wet, in sun and in shade, and from the ground at roof height. We suggest holding the sample against the existing stonework or the neighbouring roofs, and tipping a little water across it. Colour that looks right on a kitchen table can read very differently from the lane below.
Weathering and ageing
Natural slate does not need painting or sealing. Over the years the surface changes with weather and with whatever grows on it. Some slates hold their colour closely; others pale or gain a rust-coloured stain if the stone contains iron minerals. A supplier's data sheet and a visit to a roof laid with the same product some years earlier tell you more than a catalogue photograph does. Where the roof is on show from a road, that second visit is worth making before you order. Ask us for the name of the product we propose and look it up, then look at a house roofed with it. A fifteen-minute walk to see a finished roof in the same slate costs nothing and often settles the choice better than any brochure. Photograph it in the same light you will see your own roof in.
Sourced life expectancy by origin
MyBuilder's slate roof cost guide, updated 21 August 2026, separates the two best-known sources. For Welsh slate it reports a working life that regularly runs past a century; for Spanish slate it gives 75 to 100 years. The guide gives natural slate overall as 80 to 100 years or more. For comparison, it puts synthetic and fibre-cement slate at 30 to 50 years. CORC consumer guidance says well-maintained natural slate can last 100 years or more.
| Covering | Typical life quoted | Source |
|---|---|---|
| Welsh slate | Regularly past a century | MyBuilder, 21/08/2026 |
| Spanish slate | 75 to 100 years | MyBuilder, 21/08/2026 |
| Natural slate, well maintained | 100 years or more | CORC |
| Synthetic or fibre-cement slate | 30 to 50 years | MyBuilder, 21/08/2026 |
How to read those numbers
Read them as typical ranges rather than promises. A manufacturer's guarantee period tells you something different from the working life of a slate on a roof. Fixing, ventilation, exposure and upkeep all affect real life, and a slate fixed with failing nails can slip long before the stone itself gives out. For Brazilian slate, ask the supplier for the test certificates for the exact product, because working life follows the quarry and the product. Our companion page on slate roof maintenance covers the upkeep that gets a roof to the top of its range.
Thickness, size and what the data sheet tells you
Thickness is where the origins differ most in practice, and where a cheaper slate can hide a weaker product. A thicker slate is heavier, rides more firmly on the batten and tolerates knocks better; a thinner slate gives a finer edge line and a lighter roof. Neither is wrong. They suit different roofs.
Why the sums matter
Covering weight feeds straight into the structure. The Planning Portal puts the trigger at a covering at least 15 per cent heavier than the existing one, and approval under the Building Regulations then follows. Approved Document A treats a load increase above 15% as significant. Swapping one slate for a heavier one on the same roof can matter, and so can replacing a lighter covering with slate. Ask the supplier for the weight per m² of the exact product, and we compare it with what is coming off.
Size and headlap
Slate comes in standard sizes, and the headlap, the amount each slate overlaps the one two courses below, depends on size and pitch. Cupa Pizarras, a Spanish slate producer, publishes the figures: for a 500 mm by 300 mm slate in moderate exposure, the headlap is 115 mm at a pitch of 20°, 105 mm at 22.5° and 95 mm at 25°. BS 5534:2014 gives 20° as the minimum pitch for natural slate at moderate exposure with a 500 mm slate and 115 mm overlap. These apply to the product tested, so check the data sheet for yours.
Our page on pros and cons of slate explains why that headlap and pitch matter for the weather resistance owners expect.
What each source costs per square metre
On price the two best-documented sources separate cleanly. MyBuilder, updated 21 August 2026, puts Welsh slate at £140 to £180 per m² installed and Spanish slate at £100 to £130 per m². Across all natural slate it quotes £100 to £180 per m².
| Origin | Installed price per m² |
|---|---|
| Welsh | £140 to £180 |
| Spanish | £100 to £130 |
| Brazilian | Priced on survey |
On a hypothetical 50 m² of slope, that is a gap of £2,000 between the lower ends of the two ranges and £2,500 between the upper ends. Whether that gap is worth paying depends on your roof and your priorities.
A price difference is only a fair comparison when thickness, size and grade are the same. Ask for both on the quote.
These are third-party national figures and do not represent what we charge. After a survey, our quote covers slate, battens, underlay, labour, scaffold and waste, so the origin you choose shows up as one number you can change. Our slate roof cost guide sets out the other pieces of a bill.
Period, listed and conservation-area roofs
If your house is old, the source of the slate can become a planning question rather than a taste one. Stroud District Council's guidance is that a listed house is protected throughout, front and back, whatever its grade. Re-roofing a listed building can need listed building consent, and a change in material or appearance is exactly what the council looks at. Stroud District has 41 conservation areas, with Article 4 Directions in five, so take the choice to the council's planners before you order anything.
Matching the existing roof
English Heritage policy, as printed in Cotswold District Council's 2000 stone slate guidance, asks that replacement stone slates agree with the originals in type of rock, colour, texture, size and depth. That policy was written for stone slates, but it shows the test a conservation officer is likely to apply: does the new covering match what was there? A Victorian terrace roofed in Welsh slate is usually best re-covered in Welsh slate. A cheaper imported slate may be visually close enough on a later house and not on an early one.
Like for like
We re-cover slate with slate, and where a roof has a particular origin we match it. Not certain what covers your roof now? The survey photographs include close shots of the slates, which we hold against samples. Should consent be needed, we explain the application. For a roof laid in stone slates rather than natural slate, the same questions are covered on our Cotswold stone roofing pages.
Choosing between them
There is no single best origin. A short checklist helps to settle which suits a given roof.
- Does the house have listed status, or sit in a conservation area? Match the existing slate and consult the council first.
- Is the existing slate Welsh? A match keeps the roof consistent across slopes and extensions.
- Is budget the main limit? Spanish slate sits lower in the sourced ranges, and a visit to a finished roof will show you whether the finish suits.
- Is the roof a long-term home? The longer life quoted for Welsh slate may weigh more than the saving.
- Is Brazilian slate on the table? Ask for the test certificates and a sample, and treat it on the evidence for that product.
What we do at survey
We photograph the existing slates, measure size and pitch, and note the condition of the battens and nails. The quote then names the slate, the size and the thickness, so two quotes can be compared. The 10-year workmanship guarantee is given to you in writing. Scaffold, offcuts and old slates leave with us.