What is Poroton?
'Poroton' is the trade name for a fired-clay block (or 'jumbo brick') manufactured to a high degree of accuracy. These blocks are formed with a honeycomb structure of vertical perforations, that reduce the material in the block (and thus the weight), whilst maintaining adequate strength and increasing the thermal resistance (lambda value) of the block. The non-face ends of the brick are keyed with vertical tongue & groove, eliminating the need for mortar between vertical faces. The high accuracy to which the block is finished makes in suitable for use with thin-joint mortar. Additional thermal resistance is possible, if the clay has been mixed with sawdust before firing, resulting in micro-pores in the finished block, and most suppliers offer such a 'thermal block'. The inner and outer face of the block is keyed ready to accept plaster.

Due to the accuracy of the blocks manufacture (a tolerance of better than one millimetre), Poroton blocks are suitable for thin-joint mortar systems, leading to a decrease in construction time, reduced mortar usage, better accuracy and higher thermal resistance (U-value) of the finished wall. Poroton blocks can be readily chased to accept wiring, can be easily cut accurately on site, and allow secure attachments to be made into the wall (pictures, shelves, etc).

In widespread use in mainland Europe for over fifty years - in Germany one in every four houses is built of Poroton blocks. Using Poroton, it is relatively economic to achieve the insulation levels of a 'passive' house (U-value better than 0.2 W/m2K- that is, one that does not need a central heating system). Even with 100mm of high-quality insulation, a conventional cavity wall would have to be over 1m thick to equal a 0.48m Poroton single leaf wall. Poroton can also be used in cavity walls and in conjunction with an exterior insulation/cladding system, to achieve high values of insulation.

Use of thin-joint mortar in constructing Poroton walls also helps to reduces heat loss as a smaller proportion of the wall's face is composed of mortar - which has less favourable thermal properties than the block. The single leaf wall is faster to build both because only one leaf is required and because thin-joint mortar can be used. The insulation applied externally is both faster and less prone to cold bridging as it covers all elements equally.