1、 Overview of roof maintenance system gutter

Gutter is an essential component in roof drainage system. It is mainly used to collect rainwater temporarily and drain it in time through downpipe.Try to use external gutter, small size, and can also be used as cornice trim.The color is suitable, the installation of exquisite gutter and veneer will undoubtedly add a lot of color to the decoration effect of the whole project.

2、 Common problems in gutter fabrication and installation

（1） Advantages and material selection of steel plate gutter

In a large workshop, the steel consumption of steel plate gutter is also a large part, but the steel plate gutter also has its own advantages, and the wind load in coastal area is generally large.If the color plate gutter is used, under the strong wind load, the color plate gutter appears weak and weak, and is easy to be lifted off by the wind suction. The design quality of the steel plate gutter also has a great impact on its durability, so the design and material selection of the steel plate gutter can not be ignored.

The most commonly used gutter materials are 1.2 mm, 2 mm or 2.5 mm thick stainless steel; 3 mm or 5 mm thick galvanized steel plate; it should be considered comprehensively according to the importance of the building, cost and the grade of other materials used.Generally, the depth of gutter in civil buildings should not be less than 250mm. It should be reasonably determined according to the clearance between the bottom of roof slab and the top of roof truss, and the space needed for slope adjustment of gutter should be considered.When determining the width, two factors should be considered: first, whether the drainage can pass through should be calculated; second, the commonly used gutter board width is 1.0m, 1.2m and 1.5m, so as to make rational use of the plate, and the gutter must be designed to be retractable in buildings with high requirements.

（2） Treatment of water leakage at lap joint of color board gutter

The gutter plate can be overlapped by 100 mm, and the lap joint is connected by rivets. If you want to ensure that the gutter is watertight, use waterproof glue.The specific method is to overlap the gutter of color board, apply two layers of neutral silica gel (acid glue and alkaline glue are not allowed to be used, and the compatibility and durability of the color board are both problematic), the sealing positions are respectively 10 mm away from the edges of the two overlapping boards, and the overlapping part is fixed with two waterproof rivets.

The center distance of each waterproof rivet is 80mm, and the two rivets are staggered. The rivets should be punched on the sealing line.Pay attention to that the rivet should be waterproof, and the rivet with penetration in the middle should not be used.

After such careful construction, the leakage problem may be that the silica gel is not fully filled; the rivets are rusted; the color steel plate at the rivet is rusted; and the silica gel is invalid.

The main reason for the failure of silica gel is the breakage of polymer chain caused by ultraviolet radiation. The life of good silica gel between steel plates should be very long.

（3） Sagging treatment of steel gutter

   In the construction of steel gutter, it is sometimes found that due to the larger column spacing and smaller gutter thickness, the gutter deflection will occur.The solutions are:

1.Under the gutter, a full-length tie beam is set to support the gutter to ensure that it will not sag, or the support is provided below.It’s better to weld gutter with a larger slope in the middle. When installing, try to avoid walking in the gutter to avoid downwarping.

2.This problem can be completely solved by using welded gutter, and the middle part of the gutter is arched to both ends with a certain slope, but the non straight gutter will increase the processing cost.

（4） Gutters and downpipes

The size of the steel gutter and the roof area is not too big, the height of the steel gutter and the purlin height should be consistent.The main thing is the number of rainwater pipes.The ponding area of rainwater pipe is generally based on the diameter of 110mm rainwater pipe, and the ponding area is not more than 180m2.The rest are calculated on this basis.It won’t overflow in this way.If accurate values are required, they must be calculated according to the formula.

（5） Is the slope of inner gutter needed

Theoretically speaking, the steel plate gutter can be used for slope making, and the specification stipulates that it is 5 / 1000.However, few steel structure companies will go to the slope, and it is more troublesome to deal with the unequal height of nodes only.In fact, I always think that the concept of concrete gutter is to find the slope of gutter. Because the friction coefficient of concrete gutter is large and the drainage is not smooth, it is required to make slope.The steel plate surface is much smoother than the concrete, and the resistance to water is very small (the friction coefficient is small). Moreover, due to the steel plate gutter stiffness is large, if the stainless steel gutter, the gutter bracket is generally added, and the water will gradually drain out, the load is small, and the deflection will not be very large. Therefore, even if there is water accumulation, it will evaporate quickly.In addition, the rainfall in Northwest China is quite small, so it is not necessary to find slopes for gutters.In addition, the outer gutter plays an aesthetic and decorative role. It is difficult to make the gutter neat and uniform when installing its outer edge after slope finding, so the outer gutter does not need to be sloped.

In fact, it is very difficult to find the slope of the inner gutter. Especially when the steel plate gutter is used around 9m, there will be deflection in the middle of the span, and the part placed on the top of the column will be higher. It is impossible for downpipes to be made in the middle of the span. Even if the chloroprene rubber waterproof layer is used to find the slope, it can only be slightly flat. Generally, if you go to the roof after raining, there will be water accumulated in the depression,Therefore, we have repeatedly asked that the corrosion resistance of steel gutter must be better.However, it is not easy to find the slope for the colored board gutter at all. Such data can be obtained by calculation. If there is a downpipe of 9m, the height difference between the two ends of the gutter needs to be 45mm.This is very difficult to make, and the overlap of gutter is also very difficult to deal with.

If it is in rainy areas in the south, it is recommended that the slope of the inner gutter should be 2%. In this way, attention should be paid to the design and fabrication. When designing, the cross sections at both ends of the gutter should be divided into high and low sections. The steel plate cutting should be cut according to the slope. During fabrication, the high section and high section should be welded, and the low section and low section should be welded, so as to make a full-length inner gutter with slope.

In a word, whether to find the slope of the gutter depends on the local climate conditions. In the rainy area in the south, it is not allowed to refuse to find the slope because of the difficulty in finding the slope. Only by combining with the construction specifications and according to the actual situation of the project can we make a suitable scheme to achieve perfection.

（6） Design improvement of steel gutter

In the field construction, many design defects can be found, which brings great trouble to the processing, manufacturing and installation. For example, in the design of steel plate combined gutter, the gutter designed with old design ideas sometimes brings inconvenience to the construction. Why does the bottom plate and outer plate of the gutter have to be 90 degree straight? When the upper edge of the gutter is strengthened by brace, the bottom plate and outer plate of the gutter must be connected vertically,The middle of the outer plate of the gutter is slightly raised, and the decorative panel of the gutter cannot be close to each other during installation.When welding the outer plate and the bottom plate, a certain angle will bring convenience to the installation of gutter hemming. After the installation of the large edge under the gutter, the height of the uplift can be ignored, and the soil dust is not easy to adhere, so the cleaning times are reduced.Although it is a small discovery, it has reduced a lot of human and financial resources.

（7） Envisage the development of new material gutter

At present, stainless steel plate is one of the most commonly used components in the factory building. I think the most difficult one is the steel plate, which is not good for corrosion protection.In fact, the problem of gutter in engineering has been difficult to deal with. Due to the nonstandard fabrication and installation of steel gutter, the problem of waterproof and leakage has been unsatisfactory.So it is necessary to develop new material gutters.Whether the structure of gutter can be completed by adding purlin under plastic steel.I think it’s possible to cover the steel gutter with hot sprayed hard plastic to complete the required process.

3、 Conclusion

To sum up, in the steel structure roof maintenance system, to make the gutter play its due use function and play a good decorative effect, the following principles should be followed:

1.The rationality of the design.According to the local environment and roof area, practical, economical and beautiful gutters should be designed.

2.Strictly control the quality.From the lofting to calculate the size, reduce the error, to avoid the deformation of components in the production and transportation.

3.Fine installation.Skilled and meticulous installation will make the decoration effect natural.

The above summary is from the experience and discovery of the construction site, the building structure also often shows the individual characteristics, so the appropriate construction scheme should be formulated according to the actual project.Only by accumulating experience and being good at innovation can we make excellent projects.