Abstract: An environmentally conservative and more cost-effective apparatus and method for protecting architectural-building construction work in progress from potential damaging effects of rain-storms, temporarily sealing-off exposed roof and wall structures from penetration by water; -heretofore only facilitated by use of awkward to handle disposable plastic-film sheets or general use tarpaulins. The new specialized tarp-system employs a modular array of prefabricated rectangular tarp-panels fabricated from flexible imperforate light-weight/high-strength material sized both for easy one-man handling which proportional dimensions are quickly and easily assembled over exposed-framing of a building. Each identical tarp-panel and optional ridge-panel employs either a linear anchoring-strip device, or a plurality of spaced apart perimeter and field-area grommethole reinforced points, either of which accepting easily removable nail or screw fasteners.