Metal roofing is a form of roofing that uses metal sheets as the roofing material, combining the structural layer and the waterproof layer into one. There are many kinds of metal sheets, including galvanized sheets, aluminized zinc sheets, aluminum alloy sheets, aluminum-magnesium alloy sheets, titanium alloy sheets, copper sheets, stainless steel sheets, etc. The surface of the sheet can be painted, mainly PE/PE, SMP/PE, HDP\PE, and PVDF\PE four kinds of paint treatments, paint can strengthen the use of the sheet life, respectively, 5–8 years, 10–15 years, 15–20 years, 20 -25 years or more.
Zinc roofing sheet design factors are to be considered.
Load-bearing
Bearing construction load, rain, dust, snow pressure, and maintenance load. zinc roofing sheet’s load-bearing performance is related to the cross-sectional characteristics of the sheet type, the strength and thickness of the material, the way of force transmission, and the spacing of purlins (sub-purlins).
Wind pressure resistance
Resisting the maximum local wind pressure, the zinc roofing sheet will not be pulled off by the negative wind pressure. The wind resistance is related to the clamping force of the metal roofing sheet and the fixed seat, and the spacing of the fixed seat.
Sound insulation
Sound is prevented from being transmitted from outside to inside or from inside to outside. The sound insulation effect is expressed in decibels of sound intensity difference between the two sides of the metal roofing layer, which is filled with sound insulation material (usually filled with insulation wool). The sound insulation effect is related to the density and thickness of the sound insulation material. It should be noted that sound insulation materials do not have the same blocking effect for different frequencies of sound.
Anti-percolation
Rainwater is prevented from seeping into the zinc roofing sheet from the outside. Rainwater enters the metal roofing sheet mainly through the lap joints or nodes. To achieve the function of impermeability, it is necessary to use sealing washers at the screw openings and then adopt concealed fixing, treat the lap joints of the sheets with sealant or welding, preferably with through-length sheets to eliminate laps and carry out tight waterproof treatment at various node parts.
Lightning protection
Lead lightning to the ground to prevent lightning from penetrating the zinc roofing sheet into the room.
Daylighting
Improve indoor lighting during the day through skylights to save energy. Arranging light panels or light glass at specific locations of the zinc roofing sheet, the service life of the skylight should be considered to be coordinated with the metal roofing sheet, and the water-proof treatment should be done at the connection between the skylight and the metal roofing sheet.
Safety devices
Set up fixed facilities on the metal roofing sheet to protect the safety of construction personnel and maintenance personnel.
Anti-ice column
Prevent rain and snow from forming icicles at the gable ends.
Aesthetics
Zinc roofing sheet has a good texture and pleasing color.
Control of thermal expansion and contraction
Control the shrinkage and direction of the zinc roofing sheet. Ensures that the metal roofing sheet will not be damaged by the stress caused by thermal expansion and contraction in areas with large temperature differences.
Thermal insulation
Stops heat transfer on both sides of the metal roofing sheet to stabilize indoor temperature. Insulation function is achieved by filling insulation materials (commonly used are glass wool and rock wool) under the zinc roofing sheet, the insulation effect is expressed in U value, and the unit is W/M2K. insulation performance is determined by the following factors: insulation cotton raw materials, density, thickness; insulation cotton humidity, metal roofing panels and the lower structure of the connection method (to prevent the “cold bridge “ phenomenon); metal roofing layer of the repeated ability of heat radiation.
Sound absorption
Reduce the reflection of sound and reduce the echoes in the room. Sound absorption function is achieved by laying sound-absorbing cotton on the bottom layer of metal roofing and punching holes in the bottom plate. The sound absorption performance of metal roofing is expressed by the sound absorption coefficient a.
Damp-proof
It prevents water vapor from condensing in the bottom layer of the zinc roofing sheet and the metal roofing layer and drains the water vapor from the metal roofing layer. The solution is to fill the metal roofing layer with insulation wool, lay a waterproof membrane on the metal roofing bottom sheet, and have ventilated nodes on the metal roofing sheet.
Fire Protection
In case of fire, the metal roofing material will not burn and the fire will not penetrate the metal roofing panels.
Ventilation
Air is exchanged between the interior and exterior. Vents are provided on the metal roof.
Avalanche prevention
Snow barriers are installed on metal roofs in snowfall areas to prevent the sudden sliding of snow.
Non-pollution
Metal roofing materials do not produce environmental pollution, and there is no light staining on the surface of metal roofing panels.
Normal service life
The service life of metal roofing should be equal to the main building, such as 25 years, 50 years, or 100 years.
Maintenance
It is convenient to maintain the metal roofing during the service life and reduce the maintenance cost.
Cost
Control the construction cost of metal roofing.