Put a natural slate and a man-made one side by side on a bench and the differences are obvious: one is split from quarried rock, the other is cast from cement and fibres. Put them on a roof thirty feet up and the differences shrink, which is why the choice causes so much argument. Man-made slate costs less and weighs a little less. Natural slate lasts longer, ages better and is the only option some councils will accept on a period house. This guide compares the two on the points that decide real jobs: what they are made of, how they weather, what they cost, how they are fixed, and where each belongs.
What each material actually is
Natural slate is metamorphic rock, formed when clay was squeezed and heated over a very long time until it developed a grain. Quarrymen split blocks along that grain into thin sheets, and a roofer later trims each sheet to size. Because the rock was never cast or pressed, it is dense, takes in almost no water, and keeps the colour and texture it was born with. Welsh, Spanish and Brazilian slate are all natural, and they differ in quality; our page on Welsh, Spanish and Brazilian slate compares them.
Man-made slate, usually sold as fibre cement slate, is a manufactured sheet. Cement, sand and reinforcing fibres are mixed, formed into thin slabs, cured and coloured, sometimes with a textured face to imitate split stone. Other man-made products use recycled rubber or resin and stone dust. Those are less common on the houses we see, and this guide concentrates on fibre cement because it is the usual cheaper stand-in for natural slate on UK pitched roofs.
One safety point belongs here. Fibre cement made in the older decades of the last century can contain asbestos. If your roof is old and you are unsure what covers it, do not drill, cut or break the sheets. Have a sample tested first, because that decides how the roof must be handled.
Looks and weathering
Look closely at a natural slate and you will see that no two are alike. There are slight variations in thickness, edges that are not perfectly straight, and subtle shifts in grey, blue, green or purple. That irregularity is what gives a slate roof its depth, and on a period terrace or a cottage it is the difference between a roof that looks original and one that looks new. Natural slate also holds its colour for generations. Some varieties develop a rusty tinge from iron minerals, and a poor-quality stone can fade or stain, but the best stay true.
Man-made slate is uniform by design. Every slab is the same size and thickness, which suits a modern estate house where a flat, even roof is the aim. The colour is applied in manufacture and can fade or weather unevenly over time, and the surface may take on algae and moss faster than dense stone. Good products have improved a lot, and from the street some are hard to tell from the real thing. The tell is usually the edge and the way the roof looks in low sun: real slate catches the light in patches, while manufactured slate looks uniform.
Cost, weight and how long they last
Typical UK ranges reported for supply and fit are £120 to £180 per m² for natural slate and £90 to £130 per m² for man-made. By origin, a published guide puts Welsh slate at £140 to £180 per m² and Spanish at £100 to £130 per m². These national figures give a sense of scale only; the quote you receive is fixed once we have surveyed, and the real price swings with the pitch, the number of valleys, hips and dormers, the cost of scaffold, and whether the battens and underlay also need replacing. Labour makes up a large share of any slate job, so the gap between materials is narrower in total than the per-metre figures suggest. Our page on what a slate roof costs breaks the sums down.
| Point | Natural slate | Man-made (fibre cement) |
|---|---|---|
| Typical UK range per m² | £120 to £180 | £90 to £130 |
| Appearance | Varied, with natural texture and grain | Uniform, consistent size and colour |
| Expected life | Very long when the stone is good | Shorter, and varies by product |
| Weight | Heavier | Generally lighter |
| Conservation areas and listed homes | Usually expected | Often refused |
| Repairs | Sound slates can be reused | Spare slates must match the product |
On lifespan, natural slate wins clearly. A good quarried slate can outlast several generations of fixings, which is why so many Victorian roofs are still on their original covering with the nails renewed. Man-made products carry shorter guarantees and do not have the same record behind them, because the materials are newer. The numbers the makers publish are a starting point. What a manufacturer's guarantee actually covers, and for whom, is worth reading before you sign, since many cover the product but not the labour to replace it.
Weight matters on older houses. Natural slate is heavy and some rafters struggle with it, while fibre cement is generally lighter. If you swap a heavy covering for a lighter one nothing special is triggered, but if the new covering would weigh 15% or more above the old one, building control approval is required and the rafters may need strengthening. Check this before you change materials. Our guide to how heavy a slate roof is explains the weights in more detail.
Fixing, repairs and mixing the two
Both materials are fixed by nailing through holes in the slate into battens, usually with copper or stainless steel nails. Natural slate can also be held at the tail by a hook where the roof is exposed or the slates are very thin, and our comparison of slate hooks and nails sets out when each is right. Man-made slates are often supplied with specific fixing instructions, and the maker's rules on nail type, head lap and the number of fixings per slate must be followed or the guarantee is void.
Repairs are easier on natural slate in one respect: the old slates are reusable. A roof with a few failed slates can be repaired by lifting sound ones from a hidden slope or by buying matching reclaimed stock. With a man-made roof you need the exact product, in the exact colour, and a batch that has aged the same way as the one on the roof. That can be difficult if the product has been discontinued.
It is tempting to mix, using man-made slate on the rear slope where nobody sees it to save money. It can be done, but the colours often drift apart in a few seasons, and on a semi or terrace the join with the neighbours is visible. Our page on mixing old and new slates explains what to look for. If you must mix, keep each material on its own slope with a clean break at the ridge or hip, never in the same plane.
Moss, maintenance and ageing
Neither roof is maintenance free, whatever a brochure suggests. Moss and lichen grow on both, usually first on the shaded north slope and under overhanging trees. Dense natural slate holds less water in its surface, so growth tends to be slower, and the stone itself is not harmed by it. On fibre cement the surface is more porous, so growth takes hold faster, and harsh cleaning can strip the coloured finish or roughen the face. Gentle hand cleaning and a biocide wash are kinder than a pressure lance on either material, and a lance can also drive water up under the laps.
The bigger ageing issue is in the fixings, not the face. A natural slate roof usually fails at the nail first, while the slate stays sound. A manufactured roof tends to fail in the sheet, through surface crazing, edge chipping or loss of colour. That difference matters when you plan ahead. A natural roof can be re-fixed and kept going. A tired manufactured roof usually has to be replaced whole. Keep the gutters clear, check after storms for slipped or chipped slates, and have a roofer look at the roof every few years from the ridge.
Where each material belongs
Natural slate is the right choice in four situations. The first is a listed building or a house in a conservation area, where the council expects like-for-like replacement. Check with your council's conservation officer before changing the material, because a switch to manufactured slate may need consent. The second is any house where the roof is a visible feature, such as a period terrace, a farmhouse or a prominent corner plot. The third is a house you mean to keep for a long time, where the longer life offsets the higher price. The fourth is a roof where reclaimed slate is available and the structure carries the weight.
Man-made slate is the right choice in a different set of cases. A modern house with a plain roof and no planning restriction, a budget that will not stretch to stone, a deck that struggles with weight, or an extension roof where a slate look is wanted but the cost has to stay down. It also suits a replacement where the roof was already covered in a similar manufactured product, and the owner wants consistency.
Planning is worth a check in any case. A change of covering in a conservation area or on a building with an Article 4 direction can need consent even when the house is not listed. Historic England publishes useful background on traditional roof coverings at historicengland.org.uk, and your council's planning team can tell you what applies to your street.
How we help you choose
You do not need to settle this from a brochure. Our free survey includes photographs of your own roof, the existing covering, the rafters and the details around the edges, and the report says which material we would use and why. If your slates are sound and the real problem is the fixings, we say that before we talk about replacement. Where a new covering is the right call, you get a price in writing that does not move, and the work carries our 10-year workmanship guarantee. For the full range of work, see slate roofing in Basingstoke, or message us on WhatsApp or ring 01256 213956 to arrange a visit.
