Outdoor kitchen: which stone to choose

An outdoor kitchen lives in conditions no indoor worktop ever meets. Before choosing the stone it pays to list the enemies, because every material fears a different one:

• Sun and ultraviolet light: they heat the surface, fade materials that contain resins and dull polished finishes.
• Frost: water that has entered the pores expands as it freezes and, cycle after cycle, flakes the more absorbent stones.
• Rain and standing water: they leave rings and limescale deposits and feed moss and staining on porous stone.
• Salt air: by the sea, salt-laden air corrodes ordinary metals and works its way into unprotected surfaces.
• Kitchen acids and grease: lemon, wine, vinegar, tomato and hot oil are the harshest test for marble.
• Live heat: embers, flame and oven impose temperature swings that most building materials simply cannot take.

Granite is the most trouble-free natural stone for outdoor use: an igneous rock, dense, barely absorbent, indifferent to frost and to kitchen acids. An absolute black or grey granite worktop stays as it was for decades, and a flamed or brushed finish also makes it slip-resistant. Its one limitation is aesthetic: it lacks the veining of marble.

Quartzite brings the two worlds together: born of quartz sand compacted under pressure, it is harder than granite and resists acids, yet offers veining and translucency that recall the finest marbles. Mind the name, though: some stones sold as “quartzite” are in fact marbles or dolomites, and sensitive to acid. The test is done on a sample, with a drop of lemon juice.

Marble is calcium carbonate: beautiful, but it reacts to acids and absorbs liquids. Outdoors it is used with three precautions: a honed or brushed finish rather than a polished one (under sun and rain a polish dulls within a few years), a water- and oil-repellent sealer renewed over time, and a place on serving surfaces and side panels rather than where the lemon is cut. Roman travertine, an open-pored limestone, must be filled and sealed: treated that way it holds up superbly, as the baths and palaces of Rome attest. Pale stones, finally, heat up far less in the sun than black ones.

Sintered stone (Dekton, Laminam and ultracompact surfaces in general) is made from natural minerals pressed and fired at very high temperature: it has no pores, does not absorb, fears neither frost nor ultraviolet light, will not stain with wine and tolerates a hot pan set down on the surface. It is today the most recommended material for outdoor kitchen worktops, in slabs of 1.2 or 2 cm; marble-effect colours give you the veining without its demands. The edge is its one delicate point: it is drawn with a small chamfer and protected during installation.

Stainless steel is the choice for the working parts: sink bowls, grills, drawers and cabinets beneath the worktop. By the sea it must be grade 316, which resists salt far better than grade 304, prone to pitting. As a worktop, steel gets very hot in the sun and scratches: we therefore recommend it alongside stone, not in its place.

Here the choice is not a matter of taste. A lit barbecue goes from air temperature to several hundred degrees in minutes and is cold again by night; in winter the frost finds it. Cement and traditional masonry contain bound water and aggregates that expand at different rates: with every heat cycle the inner structure micro-cracks, the mortar joints open and after a few seasons cracks, spalling and settlement appear. That is why for outdoor kitchens and barbecues we use neither cement nor masonry.

Refractory stone was born for fire: it is the very material of bread ovens and of the fire chambers of fireplaces. Its thermal expansion is minimal, it takes the temperature swing without cracking, and it stores heat and gives it back slowly, which makes for more even cooking. Our refractory stone kitchens bring together a wood-fired barbecue, an arched-mouth oven, a sink, worktops and log stores in a single architecture, with a steel hood to carry the smoke away. Above, the worktop may be granite, quartzite or sintered stone; in direct contact with the flame, refractory stone only.

An outdoor kitchen is a small building, and it is designed as one.

• The structure: either a stainless steel or aluminium frame clad in stone or porcelain, or a solid block of marble, travertine or granite carved as one piece, like the monolithic islands we design in Aprilia. Solid stone fears nothing, but it is heavy: the base must be calculated for it.
• The worktop: a typical thickness of 2 or 3 cm for natural stone, 1.2 or 2 cm for sintered stone; a barely perceptible fall towards the outer edge lets water run off, and a drip groove cut beneath the overhang stops it creeping back onto the side panels. Joints between slabs are sealed with flexible products, never with rigid mortar.
• Built-in elements: grill, gas hob, fryer, sink, outdoor refrigerator. Every cut-out is made in the workshop on numerically controlled machines, with rounded internal corners so as not to create weak points, and with the air gap the appliance maker prescribes around heat sources.
• Water and power: drains with a trap and a stopcock for draining down in winter, sockets and lights rated for outdoor use, certified gas supply.
• The base: a perfectly level, drained plinth, because water pooling beneath the kitchen is the first cause of staining and frost damage.

At the poolside the stone lives with chlorinated or salt water, wet feet and the midday sun. It needs slip-resistant finishes (brushed, bush-hammered, sandblasted) and pale stones that do not burn underfoot: travertine, pale quartzite and sintered stone are the best suited, and the pool coping itself can be worked in the same stone as the kitchen, as we do for our stone-clad pools. The counter and the cooking zone are kept at a distance from the water, out of reach of chlorine splashes.

On a terrace the first question is weight: a 2 cm slab of marble or granite weighs roughly 55 kg per square metre, and a solid-block island several hundred kilos. Before drawing anything we check the load-bearing capacity of the floor, then choose: thin sintered stone on a light frame where the capacity is limited, solid stone where the structure allows it. The route for the slabs (stairs, lift, crane) and the waterproofing beneath the base, which must not be pierced, are checked too. Wind at height, finally, calls for doors and drawers with secure catches.

Michelessi has been working marble in Aprilia, between Rome and Latina, since 1976, and builds bespoke outdoor kitchens for gardens, terraces and poolsides in Italy and abroad. If you are planning yours, write to us or call us: we will advise you on the right stone for your climate, prepare the 3D design and agree lead times and a quotation with you.