wooden block houses up to 45m2 Venezia Tarragona Marbella Granada Ibiza Livorno Madrid Barcelona wooden block houses up to 75m2 Milano Valencia Ravenna Rhodos Seville Malaga Creta wooden block houses above 75m2 Corfu Karpenisi Firenze Atene Nikos Santorini San Marino technical characteristics of block houses introduction tongue-and-groove joint construction durability fireproof construction impregnation logs wall insulation and heat transfer underlying construction floor roof structure roof windows doors