The question of insulation came up in discussion with a friend and he mentioned insulating the cavity. On my encouragement he is going to look into his roof insulation before he does anything, but what then puzzled us is that this is a brick built house (cca. 1905) but the total wall thickness is the best part of 600mm - allow say 75 to 100mm for the strapping and plasterwork, but that still leaves 400 to 500mm of brickwork and cavity which I find difficult to explain in terms of a standard 125mm brick and cavity wall.
Can anyone explain please ?
Rob