Application of roof cushion in slope roof waterproofing

Most sloping roofs are not waterproof by themselves. The purpose of the pitched roof is to drain water, and the formation of an ice dam will cause water to accumulate on the roof, and the water will find its way into the house. When the moisture from the ice dam seeps into the gaps in the exterior walls, the walls and insulation become wet, which is the ideal environment for mold growth.
Roof bedding entered the U.S. market in the late 1870s as a means of protecting traditional pitched roofing from leakage due to ice DAMS in cold environments. Problems can arise in cold weather when water accumulates beneath the shingles after ice DAMS form.



Later, bedding materials began to be applied to buildings in mild climates to prevent roof leakage caused by wind and rain accumulation, or to protect complex joints that might leak even under normal conditions.

Before the cover plate is installed, the cushion is placed on the base of the roof panel. The sticky roof cushion has become a standard component of many high-grade slope roof systems. When the roof design changes to the non-traditional direction, the role of the roof cushion material becomes more critical. The correct use of bedding materials accelerates the construction process and ensures that the roof is protected from the effects of climate change.

Not all bedding materials are made to the same standard. When choosing a product, three key indicators need to be considered: exposure time limit, lap integrity, and dimensional stability.



Exposure time limit:

The roof bedding material is not designed for permanent exposure to sunlight, and beyond the specified time limit, ultraviolet light will cause the degradation of the physical properties of the bedding material. To choose a bedding material wisely, it is necessary to consider how they will perform their intended function within the roofing assembly system.



Lap integrity:

Metal plates, or any pitched roof cover, need to be mechanically fixed to the structural plates. In many cases, this means that the cushion material will be penetrated by most of the screws. Under normal circumstances, the waterproof layer should be avoided as far as possible, but many times it is inevitable. However, if the roof bedding material is well designed with a high quality self-adhesive layer, it can seal the penetration. Astme 1970 is a test standard for self-adhesive polymer modified asphalt coil used as protective cushion for anti-ice dam on slope roof. In this standard, the self-sealing performance of the nail is tested by placing the penetration in a water head at a depth of 127mm to see if there is leakage.



Dimensional stability:

Heat resistance is a problem in all roofing, and is becoming a real concern in some metal roofing, especially those with complex shapes. Copper, zinc and some alloy roofing panels often cause abnormal temperatures and can exceed 93 ° C, even in mild climates. In other types of roofing, such high temperatures may also occur when sunlight is reflected and focused on the roof if it is located under a row of Windows or in an area where the surface is curved or sunken.



This effect is more pronounced at higher elevations, where the bedding material must be able to withstand the same amount of heat as the main roof for a certain amount of time. Heat resistance is determined by the temperature at which the material melts. To fully solve the roof problem of high temperature heating, it is best to consider the use of butyl rubber bonding layer of coil, rather than using SBS as the bonding layer. Butyl rubber has high heat resistance compared with SBS, forming a long-term stable waterproof film. In essence, it is more reasonable to consider the use of cushion materials that can be comparable to the life of other components of the roofing system.



When roofing is used on a non-metal base, such as a concrete or wooden base, dimensional stability means that the coil itself cannot produce any wrinkles, thus ensuring the integrity of the lap area. Because any wrinkles in any part of the lap area, no matter if they are severe or small, are potential weak spots that can form a leak channel.

Building owners or developers must understand the need for high-quality waterproofing, which not only protects the structure itself, but also extends the life of the structure and preserves its value.