The thickness of the webs (6) between the holes is 3.5 mm or less and the ratio fo the largest to the smallest internal widths of the hole cross-section is between 1:1 and 1:2. The distance (1) of the hole rows is 17 mm or less. The hole portion is 60 per cent or more. The holes are hexagonal and in honeycomb formation.The honeycomb pattern arrangement is such that the webs (6) are vertical to the view surface of the brick. In the mfr. of the bricks a fibre-type medium producing porosity is used and pref. involves paper fibres. The outer walls (7) of the bricks on the abutment surfaces have at most three times the thickness of the webs (6).
