What Is the Connection Solution Between UHPC Exterior Walls and Door and Window Openings? Coordinated Design of Watertightness, Airtightness, and Deformation

The junction between UHPC exterior walls and door/window openings is a critical node for waterproofing, condensation prevention, and deformation accommodation; the quality of its treatment directly affects the building's physical performance and living comfort. Qinglong Group adopts a systematic connection approach of "constructive waterproofing as the primary measure, material sealing as supplementary, and deformation coordination as the foundation," using multiple lines of defense and flexible connections to ensure the reliability and durability of this complex node over long-term use. In a high-end residential project in Nanning, this solution successfully achieved zero leakage around openings under typhoon and heavy-rain conditions.

The first line of defense is constructive waterproofing with pressure-equalization design. Between the UHPC wall panels and the door/window sub-frames, we design a continuous waterproofing cavity. The UHPC panel joints on the outer side of the cavity are sealed with weather-resistant sealant, while on the inner side, a complete waterproof and breathable membrane is installed on the door/window sub-frame and effectively lapped with the wall's waterproofing layer. This creates a "block outside, drain inside" construction: even if minute water seepage occurs through the external sealant joints, it will be blocked by the cavity and discharged through drainage holes at the bottom. All horizontal connection areas (such as window sills and lintels) must have their UHPC components set with a drainage slope of no less than 10%, and window lintels must include drip edges, fundamentally directing rainwater away from the interface.

The second line of defense is elastic material sealing. A gap of 8-12mm is reserved between the UHPC panels and the door/window frames, filled with highly elastic closed-cell foam backer rods, then sealed with a single-component silicone weather-resistant sealant with a movement capability of no less than ±25%. Sealant application must be carried out only when the UHPC panels and door/window units are securely installed and the substrates are clean and dry.

The most critical aspect is the deformation coordination design. UHPC panels and aluminum alloy door/window frames have different thermal expansion coefficients, and since the two are fixed respectively to the main structure and the UHPC framework, relative displacement is possible. Therefore, the connection cannot be rigid. We typically use "fixed-distance compression" clip-on cover profiles or decorative cover plates with slotted-hole connectors, which compress the sealing gaskets while allowing a certain degree of movement in three dimensions. Through this refined node design that combines rigidity with flexibility and sets up multiple lines of defense, UHPC exterior walls and door/window units achieve a seamless, safe, and reliable connection.