1.Roof ridge part:

The main reasons for water leakage in this part are as follows: the wave crest at the ridge is too high, and the roof ridge cover plate can not be waterproof; the longitudinal lap is not laid with waterproof, forming a gap and water leakage; the longitudinal lap of the roof cover plate is connected with rivets, and the rivets are broken due to insufficient thermal expansion and cold contraction strength, resulting in water leakage; there is no plug between the ridge roof plate and the roof panel, or the plug falls off due to nonstandard placement. 

　　2.Lighting board position:

The waterproof of lighting board is an important part to maintain the waterproof of the system. The main hidden danger of roof water leakage is the clay laying and waterproof screw in the installation of the lighting board. The type of the lighting plate does not match with that of the roof panel, and the wave crest on both sides of the lighting plate is higher than the roof panel. After the installation, the air pressure difference between the inside and outside of the lighting board is formed due to too tight sealing, and the capillary water enters into the roof from the gaps on both sides of the day-lighting board.The results show that the longitudinal lap length of the plate is not enough, and the mastic is aging and losing viscosity; the longitudinal mastic falls off; the lighting plate and color steel plate are rigid lap joint, and the gap in the middle is not sealed. 

　　3.Roof opening position: 

The opening of color steel plate roof must not only solve the appearance problem but also the roof waterproof problem. These two problems should be determined according to the opening form and the color steel roof panel model.The main reasons for water leakage in this part are: the fan opening is not waterproof treated according to the design node, and the steel plug is not laid for waterproof; the reserved area around the fan opening is small, the rainwater flow is not smooth, and it is easy to accumulate water; there is no waterproof treatment for the lap around the opening; there is no structural member around the opening, forming low water accumulation; water blocking phenomenon exists in the waterproof construction. 

　　4.Cornice part: 

The main reason for water leakage at the eaves is that the water leakage is mainly caused by the fact that the outer panels are not installed with foam plugs, and the outer panels are not pulled down; the length of the outer panels is insufficient, and the cornice is not added with water. 

　　5, gutter part: 

Lap joint and closure joint are two key parts of water leakage. Compared with reinforced concrete roof, the depth of gutter of steel structure roof is smaller, and there is no continuous waterproof structure between gutter and roof. It is difficult to ensure no water leakage when gutter is accumulated.The main reasons for water leakage in this part are as follows: there is a gap in the welding joint of the inner gutter to form water seepage; the pipe diameter of the gutter and rainwater pipe is too small to match the slope length of the workshop; there is no head plate at the end of the gutter; the length of the roof outer plate extending into the gutter is insufficient, and the water will flow back into the plant. 

　　6.Connection between brick wall and light steel roof: 

This part is easy to form a hidden danger of water leakage. The main reason of water leakage at the joint of roof panel and cement wall is that the stress is not synchronous, which leads to the cracking of bonding surface between structural wall and steel plate. 

　　7.Aluminum alloy window part: 

The connection part of aluminum alloy window with color steel wall and brick wall is one of the difficult problems of waterproof. The main reasons for water leakage in this part are: there is a gap between the wall purling and the aluminum alloy; the sealing between the lower opening of the window and the steel structure, the brick wall and the window glass and the profile is not tight; there is a large gap between the windowsill and the platform or there is reverse water phenomenon; there is no waterproof during the installation of the flashing edge closing part of the window upper opening. 

　　8.In the process of use: 

Rainwater castor has a lot of pollution and water blocking.The waterproof glue and sealant are aging and lack of necessary maintenance during use.