Sintered Stone Countertop Thickness: 9mm vs 12mm vs 20mm

Standard Sintered Stone Thicknesses in Millimetres

The thickness is a nominal product specification, measured through the slab rather than through the cabinet, substrate or finished edge assembly. The five sizes below describe useful selection routes; the chosen design and format determine what can be supplied.

Common slab thicknesses

Slab thickness	Where it fits	Countertop implication
6 mm	Backed cladding, cabinet faces and decorative panels.	Use full backing; this is not the default self-supporting kitchen worktop.
9 mm	Light-duty horizontal surfaces and slim backed details.	Continuous support is central to the design, especially at openings and free edges.
12 mm	Funtek’s preferred starting point for kitchen worktops and islands.	Level cabinetry with a planned transverse support layout.
15 mm	Worktops, larger islands and furniture needing a more rigid section.	Support still matters; review the actual span and openings.
20 mm	A more substantial straight edge and selected project specifications.	Funtek lists this as custom production; confirm the selected format, finish, quantity and lead time.

Funtek’s current fabrication and installation manual identifies 6, 9, 12 and 15 mm as standard production and 20 mm as custom production. This does not make every thickness available in every colour. For drawings using imperial units, use the millimetres-to-inches conversion alongside the nominal millimetre specification.

9mm vs 12mm vs 15mm vs 20mm: What Actually Changes?

Increasing thickness gives the slab a deeper section, more mass and greater resistance to bending when the material and layout are otherwise comparable. It does not change the locations of cabinet openings or remove the load from a filled sink. Those loads still need a path into the cabinetry or frame.

Thickness, support and slab mass

Decision	9 mm	12 mm	15 mm	20 mm
Edge profile	Slim	Thin straight edge	Intermediate profile	More substantial profile
Primary kitchen worktop	A backed, project-approved assembly rather than the general starting point.	The first option to review for a supported residential worktop.	Worth comparing for larger parts or greater section rigidity.	Compare when the project specifies a heavier section or exposed 20 mm edge.
Support approach	Continuous backing/support.	Level frame; add transverse bearing and support at openings.	Level frame with the spacing approved for the layout.	A dedicated support plan remains necessary.
Relative slab mass*	0.75 ×	1.00 ×	1.25 ×	1.67 ×
What changes the decision	A substrate can dominate the assembled thickness and cost.	An island opening or overhang can require additional support.	Availability and format are checked on the selected product.	Custom production conditions and handling weight are part of the quote.

*Relative mass assumes the same slab area and density, with 12 mm as the reference. These are calculated ratios, not measured product weights or load ratings: thickness ÷ 12. For example, 20 ÷ 12 = 1.67, so the slab material is about 67% heavier before packing, backing or edge strips are included.

Choose 12 mm first for a conventional supported kitchen worktop. Compare 15 mm when a larger finished part, furniture frame or stiffness requirement makes the intermediate section useful. Consider 20 mm when its exposed edge is part of the design or the project specification requires it. Do not move automatically to the thickest option just because the countertop includes a sink.

For 9 mm, the useful question is whether the whole assembly suits the intended use. A slim slab bonded to a rigid supported substrate behaves differently from the same slab laid across open cabinet bays. Funtek’s manual places 9 mm in continuously supported, light-duty horizontal applications; that is a more precise selection rule than calling all thin countertops safe or unsafe.

The Support Under the Slab Changes the Choice

A countertop transfers loads through its bearing points. When those points are level and sufficiently close together, the slab crosses shorter unsupported distances. A local high spot or an open appliance bay changes that geometry, even if the overall kitchen looks level.

For Funtek worktops, the manual recommends transverse support at 400–500 mm for 12 mm slabs and 500–600 mm for 15 mm slabs. Add support at seams, openings and appliance voids. These starting layouts belong to the manual’s stated conditions; a heavy commercial counter or unusual span needs its own frame plan.

For the installation sequence after the specification is chosen, see the sintered stone installation guide. This page focuses on choosing the thickness; the installation guide covers preparation, contact, joints and handover.

Slab Thickness and Finished Edge Height Are Different

A straight edge exposes the slab’s own thickness. A mitred edge joins the horizontal top to a separate vertical strip with matching bevels. The visible strip can be taller than the slab is thick, so the designer can choose a deep-looking edge without ordering a solid slab of that height.

Record the slab thickness, finished edge height and substrate or cabinet level separately on the drawing. The finished countertop elevation includes the supporting build-up, so replacing one thick-looking edge with another can also affect appliance and backsplash alignment.

A mitred strip is an edge detail, not a substitute for the support beneath an island. Keep the joint, reinforcement and bearing arrangement in the fabrication drawing rather than treating the visible edge height as a load rating.

See how a sintered stone mitered edge is made when the finished apron height must be specified separately from the slab thickness.

Sink Cutouts, Cooktops and Island Overhangs

Openings interrupt the slab section. A wide sink can leave a narrow stone strip at the front; a nearby seam or another opening can shorten the remaining load path further. Choosing 15 or 20 mm does not restore the material removed by the cutout.

Funtek recommends R10 mm as the default countertop opening radius. Its manual specifies at least 70 mm from an opening to the finished slab edge, with 100 mm preferred, and at least 120 mm between adjacent openings, with 150 mm preferred. Have the fabricator review narrow strips and seam positions before cutting.

An undermount sink needs an independent mechanical cradle or rails. These carry the basin, water and any disposer into the cabinet assembly; the stone perimeter and adhesive alone should not carry that combined load.

Use the overhang value for the actual thickness and assembly

For level, uniformly supported cabinetry and normal residential loading, Funtek’s manual gives these starting values:

Funtek overhang starting values

Thickness	Without added reinforcement	With steel/aluminium reinforcement
12 mm	Up to 100 mm	Up to 150 mm
15 mm	Up to 150 mm	Up to 200 mm

A seating projection longer than these values needs a bracket, subframe or reinforced cabinet design. Concentrated loads, commercial use, waterfall ends and mitred aprons require a specific frame plan. Do not apply another brand’s larger overhang allowance to a Funtek slab.

For example, a 300 mm seating overhang is not approved merely by choosing 12 mm: it is beyond both 12 mm starting values above, so the support must be designed before the slab is ordered. Draw the projection and its bearing points together.

Does a Thinner Countertop Cost Less?

Compare complete assemblies, not only slab prices. A thin sheet can reduce stone mass, but a continuous substrate, added framing or a mitred apron adds material and fabrication. Conversely, a straight exposed edge can avoid the work of cutting, bonding and finishing a deep fascia.

A useful like-for-like quote includes the same finished dimensions, colour, finish, sink and hob openings, edge profile, support scope, packing and destination. A 12 mm top with a tall mitred edge can involve more edge work than a plain 15 or 20 mm top; the thinner slab alone does not settle the total.

Use the weight-by-thickness guide when the handling route or shipping load is part of the decision. The relative-mass row above compares slab material only; it excludes the substrate, metal frame, sink and packaging.

Confirm the Selected Funtek Product Before Ordering

Thickness belongs to a specific product and format. For example, the current Hermes Grey product options list 6, 9, 12 and 15 mm across several formats. A design shown in those options does not establish a matching 20 mm stock item. Review custom production separately when 20 mm is required.

The same colour name also does not replace sample and drawing approval. Check the chosen finish, actual face direction and usable slab size together with thickness, especially where an island and waterfall must meet visually.

What to Send When Requesting a Quote

Send the project conditions with the thickness you are considering. They let Funtek compare available slab options and identify the factory-review points that belong in the quotation.

• Countertop size, island size, and total square meters or square feet
• Preferred thickness: 9mm, 12mm, 20mm, or unsure; include 15mm when it is being compared
• Sink type, cooktop type, and all cutout dimensions
• Overhang depth and whether seating is required
• Edge profile: straight edge, mitered edge, waterfall side, or built-up edge; include the finished edge height
• Color direction: marble look, concrete look, neutral stone, dark statement, travertine look, or mineral color
• Finish: polished, honed, matte, textured, or anti-slip if relevant
• Destination country, quantity, packing needs, and project schedule

Use Funtek’s countertops and kitchen islands project page to review the supply route. The next useful result is a matched material option and quotation with the relevant drawing-review points, rather than a price for thickness alone.