28. 外维护结构和屋顶工程。外维护结构和屋顶工程包含项目一些费用估计数最高的细列项目。门窗幕墙的费用历来根据市场状况大幅波动，而地震等自然灾害都可能影响到市场状况。此外，外维护结构可能由智利国外的其他国家制造，因此采购、制造和进口需要较长的前导时间。幕墙通常是大楼建造工程风险最高的项目之一，因为幕墙可能有制造缺陷和组装困难，导致漏水或其他维修问题。大楼屋顶工程和上层结构要求(如太阳能电池板和天窗)也尚待设计。作为风险缓解措施，牵头咨询公司将包括一名幕墙工程咨询顾问协助管理大楼幕墙的设计、制造和组装。此外，牵头咨询公司将加快外围护结构和屋顶工程的设计，以更好地确定上层结构的需要、布局、天窗以及与太阳能电池板设计的结合。咨询公司还将进行详细的实地调查以减少现场情况不明的风险及加快设计公司的聘用和有关幕墙的采购工作。
28. Exterior enclosure and roofing. The exterior enclosure and roofing comprise some of the highest cost-estimate line items for the project. The cost of window wall facades has historically fluctuated significantly on the basis of market conditions that may be affected by natural disasters such as earthquakes. In addition, the exterior enclosure could possibly be manufactured in countries other than Chile, thus requiring a longer lead time for procurement, manufacturing and importation. The facade is typically one of the highest-risk items for building construction as it is susceptible to manufacturing defects and assembly challenges, which can lead to leaks or other maintenance challenges. The roofing and the superstructure requirements (such as solar panels and skylights) for the building have also yet to be designed. As a risk mitigating measure, the lead consulting firm will include a facade engineering consultant to assist with the management of the design, manufacturing and assembly of the building facade. In addition, the lead consulting firm will accelerate the design of the exterior enclosure and roofing to better define superstructure requirements, layouts, skylights and integration with the solar panel design. It will also perform detailed site surveys to reduce the risk of unknown site conditions and accelerate procurement of the design firm and facade-related procurement.