Preface: For a long time, roof leakage has been a common phenomenon due to some factors of its own structure. In addition, the higher thermal conductivity and expansion coefficient of steel roofs make the temperature difference between colored steel plates in the roof in winter and summer, and the gap between various joints and overlapping joints is not a normal state. Therefore, the waterproofing of steel roofs has never been well solved. Below, we analyze the common structural defects and hidden dangers of steel roofs and provide a response waterproofing plan.

1. Waterproof structure and defects of color steel roof gutter

The structure of color steel roof gutters is usually in the following form:

For some projects, the water-blocking felt in the picture above was not designed.

When the slope of the color steel plate is large enough, theoretically rainwater flows down the color steel plate into the gutter without flowing outside the gutter. However, due to the large span of many roofs, they adopt a small slope from the perspective of cost. Under the influence of wind or airflow, many color steel plates will experience rainfall flowing along the lower edge of the color steel plate to the outside of the gutter, that is, inside the house. In order to avoid this situation, some roofs are specially matted at the joints of the gutter and color steel plates when designing steel structures, which is used to block the outflow of rainwater, that is, block the rainwater from flowing into the room. Although this design can partially block the outflow of water, it cannot fundamentally solve the problem of water leakage. Moreover, over time, the upper edge of the gutter will rust and rot under the action of the accumulated water felt.

Pictures of a construction site:

In the picture, we can see from the back of the gutter: the inner upper edge of the gutter has been rusted and accompanied by a lot of water stains; the gutter welds have been rusted and leaked under the soaking of rainwater (note the water droplets at the welds). This shows that traditional structural waterproofing cannot achieve perfect waterproofing, especially when the old roof is maintained or waterproofed, this structural structure brings a lot of inconvenience to subsequent work.

The picture below shows the shooting of the roof of the gutter:

In the above picture, the original design idea is to try to expose the gutter as little as possible to overcome the impact of wind or airflow on rainwater and allow the water to flow into the gutter smoothly. However, from the actual effect, the waterproofing effect is not good and affects the cleaning and maintenance of the gutters.

The gutter after sawing (photo taken after dirt is removed):

As can be seen from the figure, this semi-enclosed gutter cannot be maintained and cleaned, and the dirt inside the waterway blocks, causing serious rust in the gutter. Its service life is greatly shortened.

2. Structure and waterproof defects of colored steel ridges

Due to the edges and corners (crcrows) of color steel plates, the ridge tiles cannot be close to the wave bottom of color steel plates, which causes a certain gap between the wave bottom of color steel plates and the ridge tiles. As mentioned in the previous section, under the influence of wind, rainwater will flow into the room along this gap. Therefore, some steel structure designs also have a smaller gutter under the ridge tiles and colored steel plates. Practice has proved that even with this built-in gutter, the waterproof effect is still limited.

According to on-site observation, rainwater usually flows down along the back of the color steel plate, and the built-in gutter actually plays a very limited role. Especially for sandwich color steel plates, rainwater will penetrate down along the foam plate or rock wool, causing leakage in the entire color steel plate to occur. This brings a lot of unnecessary illusions and delays to the waterproof leak checking work.

summary:

Even with a newly built color steel roof, the gutter and ridge are its weaker links. The future waterproofing problem has actually been put in front of us the moment it is completed. In addition to some of the situations analyzed above, we can also find that the gutter has almost no slope, and long-term accumulation of dirt will cause local blockage, and rainwater will accumulate in certain parts of the gutter for a long time, so rust is inevitable. If the blockage is severe, rain may also overflow the gutter during heavy rain, and the situation is unimaginable. In addition, the water drop in the gutter is also a weak link in waterproofing.

In addition, as mentioned in the preface, various abnormal gaps (caused by temperature difference) will occur. Conventional waterproofing and leak repair methods, such as: silicone, waterproof rolls, and asphalt cannot effectively cure water leakage problems in the long run. The biggest weakness of these conventional materials is their poor weather resistance and cannot withstand the changes caused by long-term large temperature drop. In the figure below, a project used silicone glue to waterproof construction during the same period of construction, but the leakage repairs were not effective.

3. Yougu Company's gutter waterproofing plan and response method

The following figure is a schematic diagram of Yougu Company's gutter waterproofing solution. The entire waterproof system adopts coating waterproofing technology to form an overall seamless waterproofing system, overcoming the joint problems existing in waterproofing solutions such as coils.

4. Yougu Company’s Roof Waterproofing Solution

It is similar to the gutter waterproofing solution, and also uses coating waterproofing technology. Considering the harsh climate environment of the roof, a single-component waterproof coating for metal roofs with strong weather resistance was selected. In addition to having good waterproofing performance, it also has the characteristics of resistance to ultraviolet radiation. The gap between the crest and bottom of the color steel plate is filled with low foaming plastic to maintain a certain rigidity and flexibility as a whole, and can withstand the shrinkage, expansion deformation caused by hot and cold temperature differences. The application method is basically the same as the above ditch waterproofing scheme, and it also adopts a three-coating and one-fabric process.

Roof waterproof construction site diagram: