Why did my black limestone patio turn grey?

This is a well-known issue in the trade, not a defect specific to your stone. Black limestone (often sold as Kota Black) is notorious for fading from deep black to a chalky steel grey within weeks to months of UK weather exposure. Colour-enhancing sealants slow it down and can restore some depth of colour, but they need reapplying periodically — they are maintenance, not a permanent fix. We tell every customer who asks for black limestone about this before they order it, because most people are genuinely surprised to hear it.

What is the difference between riven and honed sandstone, and does it affect staining?

Riven sandstone has a natural, textured, split-face surface; honed sandstone is mechanically ground smooth and flat. The texture on riven stone breaks up marks visually, so stains are far less noticeable. Honed stone, especially in pale colours, shows oil, wine, tannin and organic staining much more starkly because the flat surface has nothing to disguise it. If you want a smooth, contemporary look, go in expecting to seal it properly and reseal periodically — honed pale stone is the single most common staining complaint in the trade.

Can I supply my own paving stone or porcelain?

We generally don't install customer-supplied paving, and we'd rather turn a job down than lay material we have no control over. If a customer is worried about handing money to us for materials, we'll specify an approved supplier for them to buy from directly instead — that protects everyone, because we can still vouch for what's arriving on site. The risk with fully self-supplied material, especially from cheap online-only importers, is that any batch variation, warping or tolerance problems become impossible to resolve: we have no commercial relationship with that supplier, and the customer often has no real recourse either.

What is the difference between rectified and non-rectified porcelain?

Rectified tiles are fired slightly oversized, then precision-cut on all four edges to an exact, consistent size with true 90-degree corners. That allows tight, even joints, typically 3-5mm. Non-rectified tiles keep their as-fired edge and looser sizing, so they need wider joints, often 8-10mm or more, to visually absorb the variation between individual tiles. For exterior paving where a clean, modern look with narrow joints is wanted, rectified is the standard. Non-rectified porcelain being sold for garden paving is usually a sign it's repurposed wall or floor tile, not a genuine outdoor paver.

Why do cheap porcelain tiles crack or shatter when they're cut?

Genuine porcelain is fired to a very dense, consistent, low-porosity body (under 0.5% water absorption). Cheap or uncertified tiles are often unevenly fired, with weak points or trapped air voids in the body. A diamond blade or grinder that would cut a properly fired tile cleanly will find those weak points and shatter the tile instead. It is one of the clearest tells that a tile was never independently tested to the standard printed on the box.

Is 10mm porcelain suitable for a patio or driveway?

No. 10mm porcelain is an indoor floor tile product. Genuine exterior paving-grade porcelain is 20mm thick, specifically to handle the point loads and freeze-thaw stress of outdoor use — occasional furniture, foot traffic, and British winters. Some cheap suppliers sell thinner indoor-grade tile, or import 18mm rather than a genuine 20mm, into the outdoor market as a cost-cutting measure a homeowner can't easily spot by eye.

What jointing compound should be used for porcelain paving?

We use Fugabella and Mapei for porcelain jointing, both of which have performed reliably for us. Some resin-bound jointing compounds that were popular a few years ago failed after their first winter or two when laid over a standard 4:1 wet mortar bed, which isn't a permeable sub-base — a requirement the manufacturers themselves specify, but that a lot of installers didn't fully account for at the time. Get the sub-base build-up right for whichever jointing product you use, not just the product itself.

Paving Stone & Porcelain: The Honest Guide (2026)

What Suppliers' Brochures Don't Tell You

Most customers choose paving by price or by how it looks in a brochure photo, then find out six months later that the perfectly honed cream sandstone stains from the first spilled glass of wine. This page is what we'd tell a friend before they order anything — not what a supplier wants you to hear.

Why This Page Exists

Almost every supplier's website describes their stone in the same three ways: durable, low-maintenance, and beautiful. All three claims are usually true right up until the finish, colour, or install detail you chose works against you. We've laid most of the materials on this page hundreds of times. This is what actually happens on site, not what sells the pallet.

Indian Sandstone

The Most Common Paving Stone in UK Gardens — And the Most Misunderstood

Names like Raj Green, Kandla Grey, Mint Fossil, Autumn Brown, Modak and Camel Dust are trade names for colour ranges, not precise geological grades — quarry sourcing and quality vary within a single named colour, which is exactly why the same "Kandla Grey" can look different pallet to pallet.

The riven vs honed staining problem

Riven (textured, split-face) sandstone hides staining in its natural texture. Honed (smooth, ground-flat) sandstone — especially in pale colours like Mint Fossil, Kandla Grey and Camel Dust — shows oil, wine, tannin and organic staining starkly, because there's no texture to break the mark up. This single combination, honed and light-coloured, is the most common staining complaint we hear in the trade. If you want that smooth, contemporary look, go in expecting to seal it properly and reseal it periodically.

Other things worth knowing:

Delamination: cheap or "seconds" grade sandstone can flake into its individual layers when it's been laid wet or drains poorly. Genuine frost-resistant stone, properly bedded with good falls, doesn't do this — it's a materials-quality and drainage issue, not a property of sandstone as a category.
The crumble test: a quick way to sense-check quality on site — crumble a corner between finger and thumb. Poor stone disintegrates into loose sand grains.
Efflorescence: a white, cloudy salt bloom on newly laid stone is extremely common and almost always temporary — it's soluble salts migrating to the surface as the stone and bedding dry out, not a defect. Don't seal over it; let it run its course first.

Limestone — Light and Black

The conversation we have most often: a customer asks for black limestone because it looks striking in photos. We tell them it will fade from deep black to a chalky steel grey within weeks to months of UK weather — and almost every time, they're genuinely surprised nobody mentioned this before. Colour-enhancing sealants help, but they need reapplying, not a one-off fix.

Limestone is calcium carbonate, denser and generally harder-wearing than sandstone — but that same chemistry means it reacts with acid. Acid-based patio and lichen cleaners, brick acid, even bird droppings and some fertilisers, can etch or bleach the surface permanently. Never use an acid-based cleaner on limestone.

Light limestone stains and etches for the same reasons as honed sandstone, and performs poorly in shaded, damp, low-airflow spots — under trees, near ponds, north-facing patios — where algae and lichen take hold on the porous surface. It's a stone that rewards a sunny, well-drained position and punishes a shady one.

Slate, Granite & Clay Pavers

Slate

Naturally riven with strong slip resistance and a layered, textured look — usually Brazilian or Indian import, in Blue Black or multi-colour "Rustic" blends. Genuine colour variation batch to batch is normal, not a defect, so order from one batch and expect natural inconsistency. The same cleavage structure that gives slate its texture also makes thin edges and corners prone to chipping, especially during cutting — a real limitation worth planning around, not a reason to avoid it for feature areas and paths.

Granite

The hardest, densest stone commonly available — near-zero porosity, essentially permanent colour, and excellent freeze-thaw and load tolerance. It's rarely used for a full patio for three honest reasons: cost (noticeably above sandstone or porcelain for equivalent coverage), a cool grey/silver/black palette that lacks the warm tones of sandstone or porcelain, and weight — thicker slabs and setts are more labour-intensive to lay. Where it earns its keep is driveways, setts, kerbs and edging, where the strength justifies the price.

Clay Pavers

Kiln-fired clay is one of the most frost-durable paving materials available, and because the colour is fired through the body rather than applied to the surface, it doesn't fade the way stone can — a genuinely strong, defensible claim rather than marketing. Common in herringbone, basketweave and stack-bond patterns for period-property driveways and courtyards. New clay paving can show efflorescence same as stone, and narrow sand joints need 6-8 weeks to bind — an aggressive jet wash before then, or repeated over the years, will strip the joint sand and loosen the surface. Re-sanding periodically is normal maintenance, not a sign something's gone wrong.

Porcelain — The Deep Dive

Why "It's Just Porcelain" Is the Riskiest Assumption in the Whole Guide

Porcelain has a reputation as the safe, modern, low-maintenance choice. That's true of genuine, properly certified exterior porcelain. It is not true of a lot of what gets sold online to homeowners looking for the cheapest tile they can find — and the two can look identical in a listing photo.

Through-body vs printed surface

Most porcelain paving is manufactured with the stone or wood-effect pattern digitally printed onto the surface before firing, not coloured all the way through. Genuine through-body (or "full-body") colour porcelain, where the colour runs the entire thickness of the tile, is the minority product. This matters the moment a tile chips or gets cut: on printed porcelain, that reveals plain grey or buff ceramic underneath, visible as a pale ring around the damage or along every cut edge. On genuine through-body porcelain, a cut or chip shows the same colour through the material. If a supplier can't tell you which one you're buying, assume it's printed.

Rectified vs non-rectified

Rectified tiles are fired oversized, then precision-cut on all edges to an exact size with true square corners, allowing tight 3-5mm joints and a crisp finish. Non-rectified tiles keep their as-fired edge and need wider joints, often 8-10mm+, to visually absorb the size variation between tiles. Non-rectified porcelain marketed for garden paving is usually repurposed wall or floor tile, not a genuine outdoor paver.

✔ The standard for porcelain tiles (BS EN 14411) permits real tolerance — up to roughly ±2mm on non-rectified tiles and ±1.5mm on rectified, and warpage that can technically comply at up to around 6mm of bow across a large 1200×600mm tile. A properly certified product from a reputable manufacturer will typically sit well inside that ceiling. Cheap, uncertified stock often exceeds it — which is exactly what shows up on site as the 2-3mm corner-to-corner difference and visible bowing we regularly see when a customer brings us cheap online tiles.

Why cheap porcelain fails on site:

Cracking when cut: uneven firing leaves weak points in the tile body. A blade that cuts a properly fired tile cleanly will shatter one with trapped air voids or inconsistent density.
Warping causes lippage: a bowed tile can't sit flush with its neighbours, leaving proud, rocking edges after laying — a trip hazard and a comeback waiting to happen.
Thickness matters structurally, not just visually: genuine exterior paving-grade porcelain is 20mm thick, built for the point loads and freeze-thaw stress of outdoor use. 10mm porcelain is an indoor floor tile. Some cheap suppliers sell thin indoor-grade stock, or 18mm instead of a genuine 20mm, into the outdoor market — a difference a homeowner can't easily spot by eye.

Slip resistance

Look for an R11 rating (the oil-wet shod-foot ramp test) as a sensible minimum for a UK patio that will regularly be wet, or a pendulum test value (PTV) of 36 or above. R9-R10 is too low-grip for a garden. There's no independent UK body checking that every imported pallet actually delivers the rating printed on the box — a genuine certificate from the manufacturer is worth asking for.

Jointing: The Part Nobody Asks About Until It Fails

The stone gets all the attention, but the jointing compound between it decides how the patio looks after its first winter. A few years ago, resin-bound jointing compounds became the default choice across the trade — quick to lay, tidy finish. A lot of installs failed after their first winter or two. The manufacturers' own guidance is that these products need a genuinely permeable sub-base underneath — but the standard build-up most installers actually used, a 4:1 wet mortar mix, isn't permeable. That mismatch, not the products themselves, is what caused most of the failures — it's just been kept fairly quiet since.

What we actually use

Flowpoint — reliable, but sets very fast in summer heat, which can leave a haze if it's not worked and cleaned off promptly.
Steintec — a newer option we've started using with good early results. We're reserving full judgement until it's been through another year of British winters.
Fugabella and Mapei — our go-to jointing compounds specifically for porcelain, both consistently reliable.

Whichever jointing product goes down, the sub-base build-up underneath it matters as much as the product itself. Ask your installer what the manufacturer actually specifies — not just what's quick to lay.

Can You Supply Your Own Paving?

In most cases, we don't install customer-supplied material, and we'd rather not take a job than lay stone or porcelain we have no control over. If a customer is uneasy about handing money to us for materials, the middle ground is that we specify an approved supplier for them to buy from directly — that way we can still vouch for what actually turns up on site. We've never had anyone refuse that arrangement, but if someone insisted on using a supplier we hadn't approved, we'd walk away from the job rather than install it.

The reason isn't control for its own sake. If material turns out to have a batch shade mismatch, poor tolerance, or warping, and we supplied it, that goes straight back up our own trade relationship with a supplier we have leverage with. If a customer self-supplied it from a cheap online importer, there's often no real recourse for anyone — and the customer understandably, but incorrectly, tends to blame the installation rather than the material.

We've used London Stone for years — reliable, genuinely helpful, and their showrooms mean customers can see and feel the actual stone before it's ordered, not just a photo. For small jobs using a common, popular stone like Kandla Grey or Autumn Brown sandstone, we'll sometimes use a cheaper local supplier where the sourcing risk is lower because it's such a widely available product.

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