Reasons for roof leakage in lightweight steel structure factory buildings

Due to its simple design, lightweight, high strength, easy production and installation, large spatial span, short construction period, and low price, lightweight steel structure factory buildings have become the first choice for many enterprises. However, the large-scale construction time of lightweight steel structure factories in China is still relatively short, and some production technology and construction process problems have not been well solved. Therefore, in the construction and use of factories, there will still be a major quality problem of factory water seepage.
According to the causes of roof leakage, there are mainly the following points.
Design factors
1) According to the Technical Specification for Steel Structures of Light duty Buildings with Gabled Frames (CECS 102:98), the roof slope of light duty buildings with portal frames should be taken as 1/8~1/20, and the maximum value should be selected in areas with heavy rainfall. In practice, due to cost saving and other factors, the construction party has made efforts to minimize the slope of the roof as much as possible. At the same time, designers often apply standards and ignore the actual situation of the building. This has resulted in many projects having roofs with too small slopes, preventing rainwater from entering the ditches in a timely manner and causing the roof to accumulate water, leading to roof leakage.
2) Due to the lack of understanding of regional rainfall in the design, the roof slope is relatively gentle and the cross-section of the gutter is small.
3) Lack of node design, arbitrary selection of nodes by various construction companies, insufficient height of roof parapets, improper or insufficient position of pipes and exhaust ducts outside the roof, resulting in difficulty in constructing waterproof layers.
4) Improper template selection: Two types of templates, namely hidden buckle and bite, are usually not a problem if installed properly on site. If the board is directly connected using self tapping screws, even if the on-site treatment is good and the waterproof adhesive is good, it will still leak due to the thermal expansion and contraction of the panel.
5) The design of the roof opening is not comprehensive enough. During the construction process, it is not allowed to cut holes arbitrarily, and waterproof work should be done inside the holes.
6) The thickness of the color plate in the enclosure area is too small. After long-term use, the outer plate may be corroded or deformed due to temperature, resulting in an increase in the gap between the plates.
7) The roof rainwater pipe network is not equipped with drainage devices according to the regulations. When the rainfall intensity exceeds the drainage capacity of the drainage system, it will cross the lap joint and even overflow the roof, causing safety accidents.
8) The number of sewage pipes is insufficient, and the distance and duration of rainwater flowing along the gutter are long, resulting in water accumulation; There is no L-shaped closure added above the outer panel of the exterior wall, and there is a risk of leakage in the ditch.
9) The design of the color steel flashing device is not reasonable enough to achieve the purpose of waterproofing.
Construction factors
1) During the construction period, there was no attention paid to the protection of the roof, and the roof was trampled indiscriminately, resulting in a decrease in its flatness and the formation of cracks. The amount of sealant used was insufficient, the position was incorrect, too many rivets were used, and waterproof measures were not taken properly.
2) The drainage ditch has not undergone anti-corrosion treatment, and some construction companies only spray anti rust or asphalt coatings on the drainage ditch. After a certain period of time, the drainage ditch is greatly eroded.
3) Due to the large span, the roof panels of the steel structure factory have overlapping joints. Although polyurethane sealant and 138900 stitching nails are used at the overlapping joints, it is often difficult to meet the design theoretical standards during installation, resulting in rain leakage.
4) The gutter has no slope horizontally, and at least 0.5% of the slope should be left during production.
5) At critical nodes, the construction was not carried out seriously. The corners of the parapet walls and other roots are not made into arcs according to the specifications or the arcs are too small. The end of the rolled edge is not sealed properly, and the white iron sheet on top has deformed. There are few fixing points, and the sealing agent is not well sealed. The root of the pipe extending out of the roof is not tightly blocked, and the leveling layer around the pipe is not higher than the nearby leveling layer. The waterproof layer has insufficient water overflow height. Due to rainwater encountered during the construction of the insulation layer, the drainage channel got stuck and the exhaust outlet was improperly arranged, resulting in the insulation layer being soaked for a long time. Cracks appeared on the rigid roof, and at the location of the dividing joint, the waterproof adhesive was not firmly bonded to the side wall of the joint, resulting in leakage.
Construction factors
1) Due to the construction workers increasing the load without authorization during the construction period, the roof was deformed. Especially when adding loads arbitrarily to the roof purlins, causing deformation of the purlins and resulting in water accumulation on the roof area.
2) Waterproof adhesive and sealant are severely aged and lack necessary maintenance in practical applications.
3) Blockage plays an important role in preventing leakage caused by wind. It is necessary to ensure the installation position of the colored steel plate and ridge cover blockage. The blockage head between the lighting board and the ridge cover plate should be coated with organic silicon. On the roof ventilation opening, a steel blockage head should be added at the peak end of the colored steel plate.
4) When overlapping, the gap is easily affected by temperature and should be left with sufficient overlap length.
5) Water should be drained rather than blocked. Generally, sealant should be applied on the inside of the steel plate during installation, and more is better.  
6) Sufficient attention must be paid to the adverse effects of thermal expansion and contraction of the steel structure roof enclosure system, and reasonable structural measures should be taken.
Material factors
1) Plastic pipes used for rainwater pipes have poor strength, and steel structure factories are prone to damage from installation to operation.
2) Due to the thin steel plate gutter, welding seams are prone to problems.  
3) Due to the failure to select appropriate lighting and color board types according to the roof slope, the wave peaks are too small and there is too much horizontal overlap, which is not conducive to drainage.
4) The thickness of the color plate in the outer cover area is too small. After long-term use, the outer frame may be corroded or deformed due to temperature, resulting in long gaps between the plates.
5) The quality of the galvanized layer on the profiled sheet substrate is poor, and the thickness of the coating is too thin, resulting in a shorter lifespan of the profiled sheet and easy corrosion and damage.
6) The quality of self tapping screw washers is poor and prone to cracking, while glass washers are prone to aging.
7) The buckle plate has significant deformation, and the height and spacing between adjacent plates are different. The rivets of the buckle plate should be waterproof.