The roof of daylighting tile adopts water collecting tank as the indoor drainage system, but the design between the roof of daylighting tile and the water collecting tank does not specify the leakage prevention measures; at the same time, restricted by the span of the bottom steel beam, the water collecting tank needs to be installed in sections between the steel beams, while the water collecting tank and the steel beams do not specifically put forward the leakage prevention measures.

In the design, the upper part of the glass inclined roof is directly connected with the main structure, and only the silicone weather resistant adhesive is used as the surface waterproof, while the poor bonding effect between the weather resistant adhesive and the structural surface will directly lead to the occurrence of the leakage of the glass layer.

The connection between steel beams on both sides of the glass inclined roof and the wall, and between the steel beams on both sides of the glass inclined roof and the lower wall are designed with weather resistant adhesive as the anti leakage treatment method, but the bonding effect between the weather resistant adhesive and the wall plastering surface layer is limited, so the leakage phenomenon is serious during the inspection in rainy season.

In order to prevent the sliding of the inclined roof glass, the design requires adding aluminum alloy cover plate at the vertical joint of the two glasses (i.e. the top of weather resistant adhesive), and connecting the lower aluminum profile with waterproof screws. The safety problem is solved, but the possibility of water leakage is increased.

Before sealant is applied between two glass rooms and between glass and steel beams, the contact surface shall be thoroughly dusted to ensure the quality of sealant application. However, it is easy to be ignored in the construction and this key link is omitted, resulting in loose sealing and leakage.

It is another important link to cause leakage that the details between the water collecting tank and the glass room, between the water collecting tank and the adjacent steel beam are not handled properly.

Anti leakage measures

1) Before applying sealant, clean the two sides of glass, steel beam and other contact surfaces in contact with the sealant with a cloth filled with detergent, then dry the surface with a second clean cloth, and require workers to install and seal within 1h; clean the two layers of sealant with a cleaning cloth.

2) During installation and construction, the sealant between glass and glass shall be full, and the thickness of cushion sealant shall not be less than 35mm; the upper aluminum gland shall be connected with the bottom aluminum alloy grid by waterproof screws, and the two sides of the gland shall be waterproof by sealant.

3) For the connection part of glass and steel beam, the sealant is first extended into arc shape on one side of steel beam to avoid aging of sealing material caused by local water accumulation.

4) The connection part between the glass and the water collecting tank, i.e. the turning point of the aluminum-plastic plate and the connection part between the glass and the aluminum-plastic plate, is provided with cross braces under it, so as to ensure the sufficient strength of the connection part and facilitate the maintenance in the future.

5) For the connection part between the glass and the upper concrete beam, a cement mortar groove shall be made at the corresponding part of the gluing when plastering the concrete beam, and the upper part shall be made into water drop, so that the colloid can be injected into the plastering layer to closely connect with the concrete base, and the circular arc shape shall be made at the joint of the cemented concrete, so as to enhance the waterproof effect.

6) For the connection part between the water collecting tank and the exposed steel beam, the steel sheet with the same material as the water collecting tank shall be welded with the steel beam and the water collecting tank respectively, and a flow gradient of 10% shall be made to ensure smooth flow and prevent water accumulation.

7) For the connection part between the aluminum-plastic plate and the glass and the wall below the terrace, in addition to adding steel cross braces at the bending part of the aluminum-plastic plate and the bottom of the glass connection part, the aluminum-plastic plate shall extend 10cm below the plastering surface of the wall, and the surface joint between the two shall be caulked with silicone weather resistant adhesive.

8) The joint of I-beam and its lower wall on both sides of the glass inclined roof shall be bricked to 5cm at the bottom of the steel beam, and the top surface shall be plastered with waterproof mortar to an outward slope. After the steel beam is installed, the gap between the two shall be sealed with building ointment.