Invisible Induction Cooktops Under Sintered Stone and Porcelain

Invisible induction is one of the few kitchen trends that lands squarely on the fabricator's bench. Instead of dropping a glass cooktop into a cutout, the induction coils are mounted directly under the slab, and the pan sits on a protective mat on top of an uninterrupted porcelain or sintered stone surface. The homeowner sees one clean plane from backsplash to waterfall. The fabricator sees a slab that now has to act as a cooking surface, carry an appliance on its underside, and meet a set of rules written by two different manufacturers who each want their warranty protected. That is a very different job from a standard cooktop cutout, and it rewards shops that read the paperwork before they cut.

The best-known system in North America is Invisacook, which is sold through dealers and installers and mounts under compatible porcelain and sintered slabs. TPB Tech, a Spanish company, is a separate brand that builds invisible induction into its own technical worksurfaces, and Cooking Surface offers a concealed induction hob tied to a specific porcelain product. This article focuses on the under-slab retrofit style of system, Invisacook in particular, and walks through which surfaces are approved, what thickness is allowed, how to lay out and fabricate the top, how heat is handled, where warranties can be lost, and what the install looks like from the shop to the jobsite. Every brand publishes its own guide, and those guides do not always agree, so treat the numbers below as a map to the documents, not a substitute for them.

How Invisible Induction Works Under a Slab

Induction does not heat the stone directly. An alternating magnetic field from the coil induces current in the ferrous base of the pan, and the pan becomes the heat source. That is why the system can work through a slab at all: porcelain and sintered stone are not magnetic and do not block the field, so the coil can sit underneath and still drive the cookware above. The catch is distance. Every millimeter of slab between the coil and the pan weakens coupling, which is why approved thicknesses are thin and why the unit has to be pulled tight and level against the underside of the top. A thick slab or a sagging bracket shows up as weak, uneven cooking long before anything looks wrong.

Heat still reaches the stone, just indirectly. The hot pan conducts heat down into whatever it touches, so the slab under a pan gets warm and can become hot to the touch during a long cooking session. Caesarstone's own guidance for its porcelain says the surface may become hot during use and that the system should not be treated as a warming plate for extended periods. This is the reason every manufacturer insists on a silicone mat or raised risers under the cookware. The mat keeps the pan bottom from sitting directly on the slab, reduces scratching from sliding cookware, and limits the heat transferred into the top. Without it, you are asking a decorative surface to behave like a hot plate.

Material choice matters because the slab has to tolerate repeated heating and cooling right next to the coil. Engineered quartz is excluded across the board: Caesarstone does not approve the system on its quartz, mineral or outdoor lines, and Invisacook's own literature has long listed quartz as an unacceptable surface. Invisacook dealers also describe granite, marble and quartzite as not recommended. Older Invisacook manuals were looser about natural stone, which is one more reason to work from the current document set rather than a brochure someone saved years ago. In practice, the approved field today is porcelain and sintered stone, and only from brands and series that have signed off on the pairing.

Practical Guide: Specifying, Fabricating and Installing

Confirm the approval on both sides

Start with two lists: the system maker's list of approved surfaces and the slab maker's own guidance for that specific appliance. Invisacook dealers list a long roster of porcelain and sintered brands, including Dekton, Neolith, Sapienstone and Caesarstone Porcelain, but a name on the cooktop maker's list is not the same as the slab maker approving it. Cosentino, for instance, publishes a dedicated Dekton specification sheet for Invisacook that approves most active colors but excludes certain ones, and Caesarstone approves its porcelain while excluding its other surface families. Approval can also be layout-specific: the Dekton sheet addresses particular burner layouts by name. Where the guides conflict, Invisacook's own manual says the countertop maker's instructions take precedence, and retrofits into existing tops are rarely practical. Write down the exact slab brand, series, color, thickness and unit model, then find each one in the documents before you quote.

Thickness and slab build

Thickness is where published guidance varies most. Invisacook product literature describes undermount installation on 12 mm porcelain as its standard, and dealer pages describe a 12 to 20 mm range. Cosentino approves Dekton in 12 mm and 20 mm for its listed layouts. At least one installer describes 12 mm as the maximum for Invisacook, while the competing Cooking Surface hob is approved only on a specific 20 mm porcelain. The safest reading is that 12 mm is the common denominator and that 20 mm is acceptable only where both manufacturers say so for that exact unit. Never laminate or build up the edge above the coil area, and do not add a substrate or backer under the cooking zone; anything between coil and pan reduces performance.

Backing materials need the same scrutiny. Many porcelain and sintered slabs leave the factory with a mesh or fiberglass backing on the underside, and slab makers do not treat it the same way. One major sintered brand prohibits its reinforcing mesh under the system, while one porcelain brand says its fiberglass backing does not need to be removed. That difference affects how the unit seats against the slab and whether the warranty survives, so confirm the backing rule for the exact slab you are cutting before the slab goes on the saw, and photograph the underside before installation for your job file.

Layout: safety zones, seams and cutouts

Every guide defines a keep-out zone around the cooking area, but the distances differ. Invisacook's general installation manual calls for burners at least 10 cm from any open end, edge or cutout and a larger clearance between a sink cutout and the unit frame. Caesarstone asks for a minimum of 20 cm from any corner or join. Cosentino's Dekton sheet is stricter, with a 300 mm safety zone measured from each induction zone centerline to any edge, joint, cutout or drilled hole, plus an additional restricted band before any cutout or joint. Cooking Surface sets 40 cm from any joint or cut. Lay out to the strictest document that applies to your job, and draw the zones on the shop drawing so the client signs off on them.

Fabrication details

Cut and drill only in the areas the guide permits, using tooling made for porcelain and sintered material. A blade designed for ultra-compact surfaces and a properly cooled thin wall core bit reduce the chipping and micro-cracking that can turn into failures once heat cycles begin. Cutout corners must be radiused as the slab maker specifies; the Invisacook manual defers to the slab material's fabrication rules for corner rounding. Hidden edges matter too. The Dekton guide requires sharp edges on concealed joints, holes and cutouts to be removed with a small chamfer or sanding, and the Cooking Surface guide says edges and cutouts must be polished even when hidden. Do not skip edge finishing under the top just because no one will see it.

Several guides also prohibit work you might otherwise do routinely. Back-side milling or blind recesses on the underside are not permitted in the Dekton guide, and the Cooking Surface guide keeps recesses and inserts away from the hob by the same clearance as cuts. Do not rout channels for the controller cable or relieve the underside to help the unit sit flat. The only marking normally expected is a light locating mark for each induction zone centerline on the underside, made as a superficial mark rather than a groove, so the installer can position the unit exactly. Keep the underside clean and flat, protect it from scratches during handling, and label the slab orientation clearly for the install crew.

Electrical and controller

The electrical rough-in should be confirmed at the design stage. Larger multi-zone units run on a dedicated 220 to 240 V circuit in the US, while some one- and two-zone units are also offered in 110 V. The Cooking Surface guide likewise requires a dedicated supply line serving only the hob. All of this is work for a licensed electrician, and the circuit size depends on the unit model, so get the electrical requirement from the exact spec sheet rather than guessing from burner count. The controller never goes in the countertop. Every guide reviewed puts it on the cabinet front or inside a drawer, so the cabinet maker needs to know which drawer front or panel is losing space before boxes are built.

Install sequence on site

Invisacook units mount under the counter with adjustable rails or clip-style brackets, much like an undermount sink, and the Dekton guide lists approved support methods by thickness. The Dekton guide also says the system must be installed after the countertop is set on the cabinetry at the residence, and it must sit perfectly level against the slab. That means flat cabinets, a top that is fully supported and leveled, and brackets bonded and tightened exactly as the system maker describes. Caesarstone asks that a certified Invisacook installer do the work. Before the crew leaves, confirm each zone powers on, check the controller, and leave the mats and the care instructions with the homeowner.

Advanced Tips for Fabricators and Installers

Ventilation below the unit is easy to overlook in cabinet design. The induction module has its own fan, and both the Invisacook manual and the Dekton sheet call for adequate airflow underneath the countertop. Older Invisacook documentation tells owners to keep drawer contents clear of the fan and not to store small metal objects or paper in drawers below the cooking area. The Cooking Surface guide goes further, with vent and clearance requirements when an oven sits below. Coordinate with the cabinet maker so the drawer box below the cooking zone is shallow enough to leave breathing room, and so a built-in oven is not stacked directly under the unit unless the guide permits it.

Maintenance and Long-Term Considerations

Most long-term problems come from use, not fabrication, so the handoff conversation matters. The homeowner needs to understand that the mat or risers are part of the cooktop and must be used every time. Cosentino's sheet makes the mat mandatory and warns against heating empty pots and pans, and older Invisacook manuals say never to cook without the risers. Remind the client that the slab under the cookware can get hot, that the system is not a warming plate for long holds, and that they should clean the cooking area only after it has cooled. Leave written care instructions from the slab maker, because cleaning products and practices vary by brand.

Warranty is really two warranties that touch at the slab. The appliance maker covers the induction unit, and the slab maker covers the surface, but only for applications and installations it approves. Cosentino states that its warranty does not cover damage from improper use, and Caesarstone conditions coverage on following its guidelines and the appliance guidelines together. Coverage terms for the unit itself differ between dealers and model years, so give the client the current written warranty for the exact model rather than quoting a number from memory. Register the unit, file the approval sheet, the shop drawing and photos of the underside, and keep them for the life of the job.

For the fabrication side of an invisible induction top, start with the right cutting and drilling tools for ultra-compact material. The Italdiamant EvoGres Next 16" bridge saw blade and the Zenesis Carbon 2 bridge saw blade are built for sintered stone and porcelain, and the Alpha CNC core bits for porcelain and sintered slabs handle faucet and accessory holes outside the safety zone. For seams elsewhere in the run, the Tenax Mastidek color-matched cartridge adhesive is formulated for Dekton and sintered stone. Browse the full thin wall core bit collection for more options.