The short answer
Spanish slate can be good quality, and MyBuilder's 2026 slate guide quotes 75 to 100 years as its typical life. What separates a good delivery from a poor one is grade, thickness, flatness and how it splits, which you can check before it goes on the roof. Pitched against Welsh slate it is usually cheaper, and on some period and listed roofs it may not be accepted.
What the published lifespan says about Spanish slate
In MyBuilder's slate roof cost guide (updated 21/08/2026), natural slate is put at 80 to 100 years or more. Spanish slate gets 75 to 100 years, while Welsh is described as usually passing the century mark. Treat these as typical bands that move with exposure, workmanship and upkeep, and as no kind of promise from a supplier or from us.
Notice what that tells you. The gap between Spanish and Welsh slate is a matter of a few years at the low end, not a difference of kind. A roof laid with sound Spanish slate on a well-fixed set of battens can outlast the people who bought it, and a poorly chosen batch of any slate can fail early. Setting several sources side by side is the work of our guide to Welsh, Spanish and Brazilian slate; here we stay with Spanish slate alone, and the hub page on slate roofing covers the wider trade.
What to check before Spanish slate goes on a roof
Quality is something you can inspect on the pallet before a single slate is nailed down, and it is worth doing, because a roof is expensive to reopen. Ask for the supplier's grade and test information, then look at the slates themselves.
- Grade. Slate is sold in grades, and the grade tells you how much variation in thickness, flatness and finish to expect. Ask what the grade means in the supplier's own terms and have it written on the quote.
- Thickness. Thicker slates are heavier and tougher underfoot; thinner ones look finer but can be less forgiving on a roof that people walk on to clean gutters or maintain a chimney. Evenness across the delivery matters more than a single measurement.
- Flatness. A bowed slate sits proud of its neighbours, lets water under the tail and can crack when nailed down.
- Ring and cleave. Tap a slate and it should ring cleanly. A dull sound can point to hairline cracks. The face should split in clean layers without flaking.
- Colour consistency. Some natural variation is normal, and some slates weather, but a pallet with obvious mixed colours will give a patchy roof.
None of this needs a laboratory, and none of it is difficult to ask a supplier about. A slater who handles slate daily will spot most problems on a handful of slates, which is why we ask to see a sample before ordering.
Cost against Welsh slate
Price is the main reason Spanish slate gets chosen. MyBuilder (2026) gives a slate re-roof as £100 to £180 per m² installed: Welsh at £140 to £180 per m² and Spanish at £100 to £130 per m². The same source suggests £7,000 to £10,000 for a semi in Spanish slate. Treat those as general market figures, not our charges; your own number is written down after the survey. Scaffold, the number of slopes, chimneys and how steep your lane is all push it one way or the other.
Is the lower price a warning? Not by itself. Lower quarrying and transport costs can explain some of the difference. A price that is far under the range, though, is worth asking about, because a cheap slate paired with a cheap fixing and thin underlay is a poor trade. Our written quote after the survey takes in scaffold, strip, slate, battens, labour and waste, so you can set it beside any other firm's.
See our slate roof cost guide for the wider picture.
Where Spanish slate is accepted and where it may not be
On an ordinary house outside any designation, a good Spanish slate is a normal choice. The 1990 Town and Country Planning Act, at section 55, excludes works that leave the outward appearance of a building materially unchanged, so a straight swap of slate for the same slate seldom needs planning permission. The catch is the word like, since Welsh and Spanish slates can differ in colour, in how they weather and in how smooth the face is. Replacing Welsh slate with a visibly different slate can change the look of a roof.
Protected homes raise a different question: not whether Spanish slate is good, but whether it matches. Stroud District has 41 conservation areas, and its council describes listed buildings as protected throughout. Whether Spanish slate is acceptable on your building is for the council's conservation officer to say, so ask before you order. Where a Victorian terrace was originally roofed in Welsh slate, the council may expect the same.
If you are patching rather than re-roofing, matching matters even on an unprotected house; our answer on matching roof slates covers that case.
Fixing and ventilation matter as much as the slate
A good slate can be undone by the way it is hung. Nail type, headlap and batten condition decide how long it stays put. Natural slate also needs a roof that can breathe, since a roof void that stays damp rots battens whatever sits above it. Our answer on slate roof ventilation covers airflow, and the underlay and fixings come into our survey notes as separate items.
So the honest answer is that Spanish slate is good quality when the batch is sound, the grade is stated and the roof is detailed properly. We photograph your roof on the survey, and the work carries our 10-year workmanship guarantee in writing.