What is Poroton?
Poroton refers to heavily porosified clay blocks: clay mixed with polystyrene beads that burn away completely during firing, leaving a void everywhere they sat. The name comes from the German porösierter Ton — porosified clay.
The process was developed in the late 1950s by the Swedish engineer Sven Fernhof, who patented the fine porosification of the ceramic body using tiny expanded polystyrene beads. POROTON is a registered trademark — first registered in Germany in 1966, and today held by the Deutsche Poroton association. In everyday speech the name is often used as a generic term for any porosified clay block; legally it is not one.
What makes the block distinctive
- Low weight. Density typically runs at around 600-800 kg/m³ — roughly a third of an ordinary solid brick.
- Double insulation. The body insulates through its pores, and on top of that the block contains vertical air cells. In the highest grades those cells are filled with mineral wool or perlite.
- Large block formats. One block replaces a whole run of ordinary bricks, which speeds up laying considerably.
- Tongue-and-groove ends. The blocks interlock, so the perpend joint is not filled. Bedded in a thin-bed mortar a few millimetres thick, the result is a virtually thermal-bridge-free wall.
For the thickest, insulation-filled grades manufacturers quote thermal transmittance values reaching into the region of 0.13 W/m²K — a monolithic wall that can meet passive-house level without a separate insulation layer. Always work from the manufacturer’s current declaration of performance rather than a rule of thumb.
Points to watch
- Accuracy is everything. Thin-bed masonry forgives nothing. The first course must be level to the millimetre; every block after that follows it.
- Saw, do not chop. Cut closers with a block saw or an alligator saw.
- Plan the chases. Cutting into a perforated block weakens the structure. Follow the chasing rules in the applicable masonry code and run vertical services in a lining wall.
- Sound. Light and highly insulating means little mass. Separating walls need their own acoustic solution.
- Use the right fixings. Heavy cabinets and radiators need resin injection anchors with sleeves.
Related terms
- Porous brick
- Poriso brick
- Perforated brick
- Thin-bed mortar
- Thermal transmittance
- Monolithic masonry
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