## 4 A Progressive Chronicle of Masonry Provisions in Turkish Earthquake Codes (1940-2018)
### Gable Walls, Heavy Earthen Roofs, and Special Roof Systems  
Previous Turkish earthquake codes paid only cursory attention to gable walls and traditional earthen roofs, largely accepting them as local cultural norms rather than rigorously controlled design features. From 1944 [47] through to the 1961 [50] revision, references to gable geometry were effectively absent, and massive earthen roofs remained tolerated so long as single-story or low-rise contexts prevailed, as was common in rural Anatolia. Due to this hands-off approach, older documents merely advised that \"excessive heights\" or \"unstable shapes\" be avoided yet provided no numeric specifications to prevent out-of-plane tipping of gable walls or dangerously heavy roof structures. Consequently, occupant expansions frequently raised the overall roof mass or added new gables in an unregulated manner, thereby exacerbating the potential for partial or total collapse during seismic episodes. By 1975 [51], the code grew more explicit about limiting tall, unsupported gable walls. It stopped short of enumerating an absolute gable wall height, but it encouraged ring beams (hatl) at the eaves level or the top perimeter. As for earthen roofs, the 1975 [51] text vaguely warned that \"excessive roof mass\" significantly raised inertial demands on masonry walls, yet enforcement hinged on local building departments, which rarely forced rural homeowners to abandon the heavy earthen tradition. Occupant expansions that extended or modified roof lines often went beyond official scrutiny, enlarging roof mass with additional earth layers or partial second floors, while ignoring ring beam continuity at the ridges. The 1997 [52] code identified gable wall detachment as a recurrent failure mode. The text specified that gables in moderate-/high-seismic-risk areas should maintain limited height, recommended an eave-level ring beam, and if feasible, required tie columns at corners. Nonetheless, these clauses remained only partially mandatory, and occupant expansions continued to spawn non-compliant gables, especially where expansions introduced an entire second pitched roof. As for earthen roofs, the 1997 [52] document acknowledged their cultural entrenchment but recommended that multi-story masonry rely instead on lighter systems or ensure ring beams that confine the top walls. In practice, local enforcement remained minimal, allowing occupant expansions to reinforce the older pattern of heavy earthen roofs with minimal structural ties. A schematic illustration of a heavy earthen roof is given in Figure 18.  
Figure 17: Allowed unsupported wall lengths according to TBEC (2018) [3]: **(a)** Maximum allowable spans of unsupported wall segments between lateral supports, **(b)** Reinforcement requirements using vertical bond beams, **(c)** Configuration of openings within wall spans. Figure 18: Schematic of a heavy earthen roof. A more rigorous stance on gable walls and heavy earthen roofs emerged in the 2007 [54] code. The code nominally capped the height of gable walls, often requiring they remain below two meters above the last ring beam. It also advocated rebar anchorage to connect the gable apex to the underlying wall system. Simultaneously, the 2007 [54] text took a firmer line against heavy earthen roofs in moderate-/high-risk zones, except under \"special heritage\" exemptions. Occupant expansions that added or raised pitched roofs were thus theoretically obligated to follow these new numeric restrictions, but in practice, occupant expansions typically proceeded without official notice in many rural communities, preserving the cycle of top-heavy roofs or tall, unconstrained gables. Finally, the TBEC (2018) [13] completed a shift to a more performance-oriented approach, explicitly restricting tall gable walls to around 0.8 to 1.0 m above the last horizontal beam in areas of higher seismic risk and pushing occupant expansions that altered pitched roofs to incorporate ring beams or partial steel ties if the roof mass exceeded certain recommended thresholds.