Sintered stone and large slabs,
from the standard to the A-frame.

What sintered stone is

Sintered stone is made by applying pressure and heat to mineral mixtures such as clay, feldspar and sand, with no resin binder. The UK Health and Safety Executive groups it with ceramic and porcelain, and environmental declarations for sintered stone slabs describe them as dry-pressed porcelain of group BIa, the lowest water absorption group covered in our porcelain tiles guide. In China it is sold as 岩板.

That makes it a different material from engineered quartz, which is crushed stone bonded with resin. The difference matters for how it is cut and, in some countries, for how it is regulated.

The Chinese standard: GB/T 44309-2024

China published a national standard for these slabs, GB/T 44309-2024 (陶瓷岩板, porcelain slab), on 23 August 2024, in force since 1 March 2025, under the national technical committee for building and sanitary ceramics. It is a recommended standard, the T in GB/T, so it applies to your order only if the contract says so: name it, with the tolerances you expect, so the inspection has a reference.

Sizes and thicknesses

Formats are set by each factory's presses and kilns, not by the standard. Large slabs such as 1600 × 3200 mm are a common trade format, and the same face size is often offered in several thicknesses. Check the exact format, thickness and weight with the factory before you design around them, and check that a slab fits the lift, the stairs and the truck at the other end.

In the North American standard ANSI A137.3, a panel or slab is a porcelain tile of one square metre or more. Many slabs carry a decoration printed on the surface: before choosing a mitred or profiled edge, ask whether the body is coloured to match, sometimes sold as full body. On a plain body, the edge shows a different colour from the face.

Uses

• Worktops and vanity tops: kitchen, bathroom and bar counters, with cut-outs for sinks and hobs.
• Wall cladding, inside and on facades. On a facade, the fixing system is an engineering decision for the local facade designer.
• Furniture and fittings: tabletops, stair treads and sinks.
• Flooring, where the large format reduces joints and asks for a very flat substrate.

Cutting and installation

Slabs are cut with diamond tools under water, ideally on a bridge saw, a waterjet or a CNC machine, with the slab fully supported on a flat table. Make cut-outs for sinks and hobs with rounded internal corners: a square corner concentrates stress and is where cracks start. Choose a fabricator who has already worked the product, or have the factory cut the tops to your drawings before shipping.

On walls and floors, thin panels need a flat substrate and full contact. The North American installation standard ANSI A108.19 calls for mortar on both the back of the panel and the substrate, and a substrate flat to within 3 mm over 3 m. Large panels are handled on purpose-made lifting frames.

Silica dust: the cutting hazard

Cutting, grinding and polishing sintered stone releases respirable crystalline silica, the dust that causes silicosis, lung cancer and chronic obstructive pulmonary disease. UK guidance puts sintered stone at usually around 5 to 25% crystalline silica, less than the up to 95% found in some engineered stone, but not zero. Ask the supplier for the silica content or the safety data sheet, and never let a slab be cut dry.

• United Kingdom: HSE guidance on stone dust expects control at source, with water suppression, local exhaust ventilation or both, plus respiratory protection with an assigned protection factor of at least 20.
• United States: OSHA's permissible exposure limit for respirable crystalline silica is 50 µg/m³ over an 8-hour day, and the 2026 OSHA and NIOSH hazard alert on countertop work calls for wet methods, water-fed tools and local exhaust ventilation.
• Australia: engineered stone benchtops, panels and slabs have been banned since 1 July 2024. Sintered stone and porcelain made without resin are outside the ban, but cutting them must still be controlled with water, on-tool extraction or local exhaust ventilation.

Transport: upright, on A-frames or in crates

Large slabs travel standing on edge, strapped to wooden A-frames or packed in made-to-measure crates, never flat. The faces are protected from each other, the frames are built for the weight they carry, and the load is braced in the container so it cannot shift. Laid flat, large slabs break.

Unloading is the dangerous moment. OSHA's bulletin on stone slabs reports workers crushed when bracing was removed during unloading and when they stood in the fall shadow of a tilting slab. Plan it: the right lifting equipment, braces removed in sequence, nobody standing where a slab would fall.

Inspection before crating

• Flatness and warpage, measured across the length and the diagonals, against the tolerance written in the contract.
• Size, thickness and squareness, on several slabs of the lot.
• Edges and corners: chips and cracks, checked slab by slab.
• Surface: print defects, pinholes, scratches, and gloss differences between slabs.
• Pattern: for continuous-vein and book-matched series, the slabs laid out in numbered sequence, with the veins lining up across the joints, photographed before crating.
• One production lot per area of the project, as with tiles, with the lot code marked on each crate.

Book-matched slabs are pairs or sets whose pattern mirrors across the joint, like the pages of an open book. They only work in the order they were produced, so a slab broken in transit can mean replacing the whole set.