Breaking strength is the load a tile can carry before it breaks, measured in newtons. It is tested to ISO 10545-4 by supporting the tile at two points and pressing down in the middle until it snaps.
For porcelain tiles in group BIa, ISO 13006 and EN 14411 require at least 1,300 N for tiles 7.5 mm thick or more, and at least 700 N for thinner tiles. Good vitrified floor tiles often test well above that minimum.
Breaking strength vs modulus of rupture
The same test gives two results, and buyers often mix them up.
- Breaking strength, in newtons, is the actual load the tile carried. It depends on thickness, size and material.
- Modulus of rupture, in N/mm², corrects for thickness and span. It describes the strength of the material itself.
For BIa tiles the standard sets a modulus of rupture of at least 35 N/mm² on average, with no single tile below 32 N/mm². A thin tile can have a good modulus of rupture and still a low breaking strength, because there is less material to carry the load. That is why the breaking strength limit depends on thickness. See floor tile thickness.
How the test works
The lab uses whole tiles where possible, or cut pieces for large formats. Each tile is dried, placed face up on two support rods, and loaded through a third rod across the middle. The load rises at a steady rate until the tile breaks.
The report should show the result for each tile, the average, the tile size and thickness, and the span used. A single number with no detail is not enough to judge a product.
What the result means on site
The test supports a tile only at two edges, which is much harsher than a floor. On site, a tile sits on a full bed of adhesive and spreads its load into the base. A tile that passes the test performs well if it is laid correctly.
Most tile breakage on floors comes from installation, not weak tiles. Hollow spots under the tile, a soft or moving base, and point loads on unsupported corners are the usual causes. Good adhesive coverage matters more than an extra few hundred newtons.
Strength still matters for heavy loads. For trolleys, forklifts or vehicles, ask for thicker tiles with higher breaking strength and a proper base. See floor tiles for commercial and heavy traffic areas.
What to ask the factory
- A recent ISO 10545-4 report from an accredited lab for the exact size and thickness you are buying.
- Individual results and the average, not just a pass or fail.
- Both breaking strength and modulus of rupture.
- A lot test on your production for large or repeat orders.
Watch for test reports that relate to a thicker or smaller tile than the one quoted. Our founding guide on reading a lab certificate shows how to check the match.
Next step
Breaking strength is easy to test and easy to fake on paper. We have production lots tested at accredited labs and compare the report with your order. Book a free sourcing review to set this up.