Analysis of the causes and prevention of water seepage in light Steel Structure Warehouses

China's economy and the rapid development of modern industry, the need to build a number of large-scale industrial plants, and lightweight Steel Structure Warehouse has a simple design structure, light weight, high strength, easy to produce and install, plant space span, construction period is short, inexpensive, etc., is most of the foreign investment in the first choice to build factories, however, the lightweight Steel Structure Warehouse, the history of large-scale construction in our country is not long, and some of the production technology, Problems in construction technology are not well solved, therefore, in the process of construction and use of plant, there are still some unsatisfactory aspects, such as water seepage in the plant is a major quality problem of light Steel Structure Warehouse project.

1. Steel roof form

Steel structure roof, wall and other enclosure structure, generally use color steel pressure plate, its thickness is generally in 0.3 ~ ~ 1.0mm, color steel pressure plate is rolled and shaped with galvanized (or aluminum zinc plating) and other pre-painted color steel plate, the exterior of the spray paint layer. For the requirement of heat preservation, heat insulation, sound insulation effect of the building, you can use double-layer color steel pressure plate, the middle of the filler insulation materials (such as glass wool, rock wool, foam, etc.); filler materials can be filled in the field, but also can be pre-composite molding with the color steel plate factory (known as color steel sandwich panel). Building roof as the top floor of the building load-bearing and external enclosure structure, its enclosure role and façade modeling role of the whole building is crucial, is the light steel structure enclosure system leakage of the most important parts. Its main role is to resist the wind, rain, snow and solar radiation, and to bear the self-weight of the roof and the roof of the wind, snow and the load of the people on the roof. According to the materials used, there are various types of lightweight steel structure roofs, such as color compression steel plate, color steel sandwich panel, colorful linoleum tile, various lightweight roofing panels, GRC board, metal arch corrugated roofing, composite compression steel plate and so on. Lightweight steel structure roof and wall materials, the main choice of color pressure plate or sandwich panel. I supervise the Steel Structure Warehouse project, the roofing materials are mainly used finished glass wool sandwich panels or color compression steel plate. Commonly used specifications of pressurized steel plate are YX173-300-600, YX130-275-550, YX70-200-600, YX38 YX173-300-600, YX130-275-550, YX70-200-600, YX38-175-700, YX21-180-900 and other 28 types of plates. In the above specifications, there are 360° rolled edge plates, concealed fastening plates with lap joints, and nailed plates, and the purlins are thin-walled C-type or Z-type steel purlins with lighter dead weight. The slope design is generally 1/10～1/15.

2.Connection of roof panels

Steel structure system building roof panel, there are 2 kinds of longitudinal connection and lateral connection on the roof. Longitudinal connection is mainly lap, that is, the upper slope plate pressure lower slope plate, lap set special waterproof sealant plus fixed special pressure strip, and lateral connection, there are mainly the following 3 kinds of ways:  

(1) lap connection to overlap the overlap side of the pressure plate, and with a variety of bolts, rivets or self-tapping screws and so on into a whole. The connection is divided into with sealant groove and without sealant groove 2 kinds of roof screws exposed, the crest are relatively low.  

(2) Concealed fastening type connection fixed support using flat head self-tapping screws fixed on the roof purlin, and then the pressure roof panel and fixed support buckle. There is no screw exposed on the roof, but the deformation of thermal expansion and contraction can not be controlled due to the direct screw connection with the purlin.  

(3) Biting concealed fastening connection, this is a more advanced roof panel connection, the roof system through the sliding bracket to fix the roof panel, not only is conducive to roof waterproofing and maintain the integrity of the roof, but also effectively control the deformation due to thermal expansion and contraction, the connection is divided into two types of 180 and 360.

3.Leakage cause analysis

The color steel plate maintenance system itself has certain strength and rigidity, the material generally will not leak, the maintenance system leakage reason mainly in the node processing improper, the quality of the material, the maturity of the system design, completeness, structural construction and installation technology and so on also directly affects the waterproof effect of the enclosure system. Color steel plate due to the environment, temperature changes and contraction, deformation, interface and lap connection parts produce displacement, ordinary sealing tape or silicone adhesive and color plate surface bonding can not synchronize displacement and produce detachment, resulting in color steel plate roof leakage. The degree of deformation and aging of different light boards in the same time is not the same. For the same rolled edge board, Butler system waterproof performance is far stronger than the same board type imitation products; the same nail plate, different construction team installation effect is also very different. Roof leaks can be attributed to the following causes.

3.1 design consideration

(1) Portal rigid frame lightweight housing roof slope should take 1/8 ~ 1/20, in the rain more areas should take the larger value. In the actual design of the project, the construction unit to save money or other reasons, the requirement to minimize the slope of the roof, the design unit is often rigid set of regulations, do not take into account the actual situation. Thus resulting in many projects roof slope is too small, the roof rainwater can not be discharged into the gutter in a timely manner, the roof water and cause roof seepage phenomenon.  

(2) designers do not understand the local rainfall is also an important factor in the design of the roof slope is too slow, the gutter cross-sectional area is too small.

(3) the lack of node design, the construction unit arbitrarily choose the node practice, the ridge of the daughter wall height is not enough, out of the roof of the pipeline, exhaust pipe location is not appropriate or not high enough to affect the waterproof layer construction difficulties.

(4) improper selection of board type, for concealed fastening type and bite type of board type, as long as the site is properly installed, there is generally not too big a problem. If the choice of direct self-tapping screws connected to the board type, even if the site is well handled, waterproof glue is also in place, but due to thermal expansion and contraction of the panel has the performance of the same will also appear leakage phenomenon.

(5) roof hole design is not well thought out. Do not cut holes and holes at the construction site, hole waterproofing should be done.  

(6) the enclosure part of the color plate is too thin, after a period of time, the outer plate corrosion or deformation by the temperature, the gap between the plate increases.  

(7) Roof rainwater system is not set up in accordance with the norms of overflow measures, rainstorm intensity exceeds the capacity of the rainwater system discharge will exceed the lap joints, and even diffuse on the roof, resulting in accidents.  

(8) The number of downpipes is insufficient, the rainwater flows along the gutter for a long distance and a long time, resulting in accumulation of water; the upper part of the outer plate of the wall surface is not added with L-type edge fittings, and there is a hidden danger of leakage in the inner side of the gutter.