1. Pay attention to the waterproof seal of the joint.

Traditional buildings used relatively small wall and roof components, making joints along matching edges easier to waterproof. As building materials diversify, components become thinner, openings and curtain-wall areas become larger, and joint movements increase. Modern buildings also have greater heights and spans. The widespread use of precast wall and floor components makes careful joint treatment and sealing increasingly important.

Older approaches paid limited attention to joint width and the choice of sealant. Some designs did not calculate joint movement or assess the sealant’s movement capacity, simply specifying an elastic joint sealant and assuming that this would prevent leaks. This approach also appeared in some specifications and standards, reflecting insufficient attention to joint design and material selection.

Curtain-wall construction places strong emphasis on joint sealing, especially structural bonding, joint-stress analysis, and calculations of bond width and thickness. Structural-sealant application is subject to strict quality control. Waterproof joint seals, however, may receive less attention and be treated simply as silicone-sealant applications. Construction, inspection, and maintenance may not receive the same care as structural bonding. Weather sealing should be treated as an important part of the curtain-wall system.

2. Analysis of waterproof joint sealing in glazed curtain-wall roofs

(1)The joints of daylighting roof are mainly located between glass panels of building curtain wall. Because of the small thickness, slot width and relative size of the panel, the temperature change, dead weight deflection and local concentrated load may cause larger tension-compression displacement. For example, 18mm thick safety building curtain wall glass is used in daylighting roof, and the surface layer is heat reflection building curtain wall glass (heat absorption coefficient 0.83, heat capacity constant 56) . The ambient temperature range is -16 ° C ~ -33 ° C, the length of long side is 2000 mn, and the length of short side is 1500 mm. When the edge of the panel is unrestrained, the large temperature difference displacement (L) of the glass joint of the building curtain wall can be calculated as follows:

Considering wind load, snow load, earthquake, deflection of self-weight (calculated on the basis of 160) , 1.20 mm displacement of seam edge, 2.93 mm displacement of temperature difference in consideration of error and other factors, set the Factor of safety above 1.1, the displacement of seam was 3.22 mm.

(2) Joint movement inevitably deforms the sealant, which can change shape but not volume (cross-sectional area). The resulting stress may be localized. As the hardness of the sealant increases, stress becomes more concentrated at the corners, which can lead to peeling.

(3)Environmental corrosion and the potential for accidental damage from sealants are also worth considering.