Why porcelain costs more to lay — and why it is still the cheaper patio

Every quote we issue for a porcelain patio sits alongside a cheaper number for Indian sandstone, and most people ask the obvious question: why is the porcelain so much more when the slabs are not that much dearer?

Fair question. The materials are closer in price than people think. The difference is almost entirely in the labour and the preparation — and once you understand why, you can also spot the installers who are quoting porcelain at sandstone prices because they intend to lay it like sandstone. That patio will fail.

The price gap, honestly stated

On a typical 30 square metre rear patio in St Helens, we are usually somewhere around a third more for porcelain than for Indian sandstone, all in. Not double, as some people expect, but not marginal either.

Why it is harder to lay

Porcelain is a vitrified, near-zero-porosity material. That is precisely what makes it brilliant underfoot and awkward to work with.

Sandstone is porous. Wet mortar grips it because moisture moves into the stone and the bond forms naturally. Porcelain does not absorb anything — which is why it never stains, and also why mortar will not stick to it on its own. Lay porcelain the way you would lay sandstone and within two winters you will have slabs that ring hollow underfoot and then lift.

It is also considerably harder to cut. Every cut is a wet diamond cut, slower and messier than running a disc through sandstone. On a patio with a lot of returns, steps and edges, that adds up to real hours.

The step cheap installers skip

Every slab is primed. A slurry primer is brushed onto the back of the tile immediately before it is laid, giving the mortar something to key into. Then it is bedded on a full mortar bed — the entire back of the slab supported, not five dabs of mortar under the corners.

That "dot and dab" method is quicker, uses less material, and is the single most common cause of failed porcelain patios in this country. It leaves voids under the slab. Water gets in, freezes, expands, and the slab cracks or debonds. On a cold Merseyside February it does not take long.

If a quote for porcelain is level with a quote for sandstone, they are not priming and they are not laying on a full bed. You are buying a patio with a two-winter life. Martin, MAE Landscapes

This is also why porcelain is unforgiving of a bad base. The full mortar bed sits on a compacted sub-base, and the whole system is only as good as the compaction beneath it. The relevant guidance here is the BS 7533 series, whose 2021 consolidation into Part 101 brought structural design for modular paving into one document.

Falls, drainage and the wall

A patio needs to shed water away from the house. We set falls at roughly 1:80 — about 12mm of drop per metre — running away from the building. It is enough to clear water, gentle enough that furniture does not rock and nobody notices it underfoot.

Two details matter more than the fall itself. First, the finished patio level must sit at least 150mm below the damp proof course. Bridging the DPC with a patio is one of the most expensive mistakes in domestic landscaping, and we have been called out to fix it more than once. Second, where a patio abuts the house against bifold or French doors, the level is usually tight — that is where a linear channel drain earns its keep.

Slip ratings and where they matter

Porcelain is sold with a slip rating, most commonly R11 for external use. It is worth understanding rather than ignoring, because the ratings are not interchangeable.

R11 is the sensible default for a general patio. If you are laying around a pool, on steps, or on any run with a noticeable slope, go to R12 or a textured finish. Some of the very smooth, high-polish porcelains marketed for indoor-outdoor continuity are genuinely slippery when wet and covered in leaf mulch in November, and we will say so if you pick one.

The flip side is that porcelain is easier to keep non-slip than sandstone, because algae has almost nothing to bind to. A sandstone patio in a shaded St Helens garden will go green every autumn. Porcelain in the same spot rinses clean.

Fifteen years of maintenance, costed

This is where the arithmetic turns. Take the 30 square metre patio above.

And at the end of the fifteen years, the sandstone looks fifteen years old and the porcelain looks like it went down last spring. That is before you price the weekends you did not spend jet washing.

Choosing a porcelain that will not date

A few things we have learned watching patios age.

Go large format. 900x600 or larger. Fewer joints reads as more expensive, and the joints are the part that looks tired first.

Be careful with heavy patterning. The decorative, encaustic-look porcelains are striking on a showroom floor and can feel busy across thirty square metres. Where they work brilliantly is as a defined zone — a seating area framed by a plainer surface.

Match the house, not the trend. Cool greys look sharp against render and modern brick, and can look cold against a warm red-brick Victorian terrace, where a sandstone-effect porcelain gives you the tone without the maintenance.

Buy the matching steps and coping. Nothing undermines a porcelain patio like a concrete step edge. Order them with the main run so they come from the same batch.

What goes under a patio

We have talked about the mortar bed, but the layer under that decides just as much.

A patio sits on a compacted sub-base, typically 100mm of MOT Type 1 on normal ground, more where the ground is soft or where a patio is being built over a former border or made ground. It is laid and compacted in layers, exactly as a driveway is, then the full mortar bed goes on top of that.

The common shortcut is laying slabs on a bed of mortar directly onto whatever was there — old lawn, soil, or the remains of a previous patio. It looks identical on handover day. Two winters later the patio has moved differentially, joints have cracked and slabs rock. With porcelain, where the slabs are rigid and the joints are narrow, movement shows up faster and more obviously than it does with sandstone.

Ask any patio quote what the sub-base is and how deep. If the answer is vague, the number is probably low for a reason.

Jointing compounds and why they matter

Porcelain is jointed with a proper jointing compound, not with a sand and cement mix brushed in.

Because porcelain does not absorb water, a traditional sand-cement joint has nothing to bond to on the slab edges and will crack and lift out within a season or two. We use a two-part or resin-based jointing compound designed for vitrified surfaces, applied wet and tooled into the joint.

Colour matters more than people expect. A joint noticeably darker or lighter than the slab draws the eye to the grid and makes the patio look smaller and busier. We generally go a shade closer to the slab rather than contrasting, and on large-format porcelain we keep the joint tight — 5mm is plenty.

The other detail is the perimeter. Where a patio meets a lawn or a border, the edge slabs need supporting and restraining or they will eventually tip. Where it meets the house, the joint against the wall needs to be flexible rather than rigid so that normal building movement does not crack it.

The questions we get asked most

Can porcelain be laid over an existing patio? Occasionally, if the existing base is genuinely sound, level and free-draining, and if the resulting height still leaves 150mm below the damp proof course. In practice we rarely recommend it. You are building a rigid surface on a base you cannot inspect.

Does it crack in frost? Correctly laid, no — porcelain has near-zero porosity so there is no water in the body of the slab to freeze. Cracking almost always traces back to voids under the slab from dot-and-dab bedding, or to movement in the base.

Is it slippery? Less so than wet sandstone with algae on it, which is the honest comparison. Specify R11 as a minimum outdoors and R12 for steps and slopes.

How thick should it be? 20mm for foot traffic. If you want porcelain on a driveway, that is a different product and a different build-up — usually 30mm and a much heavier base.

Sizes, layouts and the pattern trap

One decision people rush is the format, and it is the one you look at every day.

Single size, stack bond. Large-format slabs in a straight grid. Contemporary, calm, and the least forgiving of a wall that is out of square — every joint line reveals it. Our default for modern houses.

Single size, stretcher bond. Half-bond, like brickwork. Slightly more traditional, considerably more forgiving of a room that is not square, and it draws the eye along its length, which is useful in a narrow garden if you run it across rather than down.

Mixed size, patterned. Three or four sizes in a repeating pattern. It suits period property and rustic finishes, but on porcelain it can look busy because the material is so uniform. It also generates more cuts and more waste, which shows up in the price.

Two practical rules. Run the long dimension of the slab across a narrow garden, not down it — it widens the space visually. And set out from the house wall, so the full slabs are where you look and the cuts land at the far edge where planting will soften them. Setting out from the wrong end is a mistake you cannot fix later without lifting the lot.

Order ten per cent extra on any patterned layout and five per cent on a straight one. Batch variation in porcelain is small but real, and matching a slab from a different batch in three years is not realistic.

More on how we build them: porcelain patios. If you are weighing up the whole garden rather than just the patio, our completed projects with costs is the most useful page on this site.