Waterproofing Construction and Maintenance of Airport Terminal Roofs II

1. Waterproofing Detail Nodes

Due to their complex shapes, high wind loads, and significant thermal deformation, airport terminal roofs require reinforced treatment at areas such as eaves, gutters, flashings, expansion joints, and pipes protruding from the roof.

1) Roof Expansion Joints: Local Shanghai codes require that metal roof panels be equipped with an expansion joint every 30–40 meters, with additional joints required at ridges, eaves, gutters, and the junctions of high and low roof sections. Waterproofing for metal roof expansion joints must address both “deformation” and “waterproofing” functions: allowing roof panels to expand and contract freely under temperature changes while ensuring that rainwater cannot penetrate under any circumstances. This can be implemented using a five-layer defense system: “grouting – waterstop – sliding support – secondary waterproofing – metal cover plate.”

2) Waterproofing layers at the flashing areas of eaves gutters, roof gutters, skylights, downspouts, and pipe penetrations extending through the roof should include an additional layer orundergo multi-layer waterproofing treatment. An additional layer should be added beneath the waterproofing layer of eaves gutters and roof gutters; the width of this additional layer extending onto the roof should not be less than 250 mm. The inside and outside corners where the roof gutter meets the roof should be rounded with a radius of 50 mm or greater, and an additional waterproofing layer should be installed to enhance the strength and flexibility of the waterproofing system. The waterproofing layer for the eaves gutter should preferably be the same as the roof waterproofing layer and laid continuously. Alternatively, waterproofing materials that are easy to install and have strong adhesion may be selected based on the specific requirements of the eaves gutter, ensuring proper overlap with the roof waterproofing layer. When two or more waterproofing layers are installed in the eaves gutter, the concrete surface of the gutter may be sloped using polymer-modified cementitious waterproofing mortar, which also serves as one of the waterproofing layers.

3) Ends of Ridge/Eave Standing Seam Panels

The ridge ends shall be sealed with prefabricated end caps to ensure a tight fit with the roof panels. The gap between the end caps and the roof panels shall be sealed with butyl tape to prevent rainwater ingress. The edges of the ridge cap panels shall be upturned to enhance weather resistance. A waterproof and breathable membrane shall be installed beneath the ridge to prevent condensation penetration. The ridge cap is made of metal sheets of the same material (e.g., aluminum-magnesium-manganese alloy) and is secured to the roof panels via 360° standing seam fastening using a specialized seaming machine. In areas prone to strong winds, the density of ridge fastening points is increased, and wind-resistant strips are used for reinforcement. In extremely cold regions, a double-layer insulation layer is added to prevent freeze-thaw cracking.
The eave ends of standing seam panels must be sealed with specialized closure components (such as aluminum alloy end caps), and the gaps must be filled with weather-resistant sealant. A drip edge (metal or PVC) should be installed at the lower end of the eave to direct water flow outward. Within 800 mm of the eave, roofing membranes (such as TPO membranes) must be fully adhered, secured with metal flashing, and sealed with sealant. Install flashing (aluminum or stainless steel), extending ≥100 mm into the eaves and overlapping the roof deck by ≥200 mm. The longitudinal slope of the eave gutter must be ≥1%, and the slope within 500 mm of the downspout outlet must be ≥5% to prevent water accumulation.

4) Bases for Equipment such as Fans and Photovoltaic Panels

For bases of fans, cooling towers, air conditioning units, and similar equipment that are cast in place with the roof structure, the construction sequence is: structural slab → slope formation layer → insulation layer → waterproofing membrane extended up to the top of the base → metal flashing + sealant. For bases of photovoltaic racks, water tanks, and small equipment placed directly on the existing waterproofing layer, the sequence is: structural slab → waterproofing layer → membrane reinforcement layer → 50mm fine-aggregate concrete load-bearing pad → equipment base → weatherproof sealant applied between the base bottom and the pad.

5) Curtain Wall–Roof Interface

Metal Roof + Glass Curtain Wall: Install a drip edge aluminum plate at the base of the glass curtain wall’s aluminum frame. Apply two layers of sealant between the aluminum plate and the metal roof panel: an outer sealant joint + an inner foam backing. The metal roof’s upstand height must be ≥250 mm. After the roof waterproofing layer is extended to the top of the upstand, fold it 50 mm into the curtain wall mullion cavity and apply sealant. If the roof consists of standing seam panels, an “Ω”-shaped flashing strip must be added to the top of the seam. After riveting the aluminum drip edge to the flashing strip, seal the entire assembly with sealant.
Stone curtain wall + concrete roof: A 2mm aluminum sheet is hung on the back of the steel studs of the stone curtain wall to serve as a secondary waterproofing layer. The aluminum sheet and the roof upstand form a “Z”-shaped fold, with a fold height of ≥100mm. A 5% inward-sloping water drainage slope is provided at the bottom of the stone panels, sloping toward the roof. A 20mm expansion joint is left between the roof’s fine aggregate concrete protective layer and the stone curtain wall, filled with polyurethane sealant.
Aluminum panel curtain wall + skylight: A stainless steel flashing plate is installed at the lower edge of the skylight glass frame; the flashing plate is continuously compressed against the aluminum panel curtain wall studs using EPDM rubber strips. The skylight drainage channels are connected to the vertical cavities of the aluminum panel curtain wall to form a structured cavity drainage system. Drainage holes with a diameter of ≥Φ8 mm are provided at the bottom of the channels and covered with insect screens.

2. Maintenance and Management of the Terminal Roof Waterproofing

Waterproofing construction follows the principle of “addressing details before large areas, starting from distant to near, applying coatings before membranes, and welding before sealing.” After the waterproofing layer is completed, a water retention test or water spray test shall be conducted to verify the waterproofing effectiveness. During roof operation, damage to the waterproofing layer must be avoided, such as by refraining from stacking heavy objects on the roof or performing welding operations.

1) Strengthen routine inspections; during flight operation downtime, conduct visual inspections of key areas such as eaves gutters, downspouts, the perimeter of skylights, equipment foundations, and lightning protection strip supports;

2) Perform seasonal maintenance: Clear debris from gutters and inspect drain grates before the rainy season; after typhoons or heavy snowfall, check for翘边 (curling) of edge flashing and cracked welds; immediately perform hot-air welding repairs for cracks exceeding 2 mm; in cold regions, test the resistance of snow-melting cables before winter and inspect eave snow guards for deformation after icy weather.

3) Periodic inspections: Conduct infrared thermal imaging surveys every two years to identify areas of water accumulation in the insulation layer; perform random peel-back inspections (2m × 2m) every five years to assess membrane aging and weld strength; establish a “Roof Health Record” to document the results of each inspection and maintenance history.

4) Repair Techniques: For minor leaks, apply a 0.8mm PVC/TPO patch with an overlap of ≥120mm and perform a full-circumference hot-air welding. For major leaks, partially remove the metal panels and reinstall a new membrane section of ≥1m × 1m. For gutter leaks, address cracks in stainless steel welds by performing TIG welding repairs followed by a re-water retention test.

3. Conclusion

Roof waterproofing for the terminal building is a critical component in ensuring its normal operation and structural safety. Based on factors such as the terminal’s operational requirements, climatic conditions, and structural form, select waterproofing materials that offer excellent durability, strong resistance to aging, and superior waterproofing performance. Emphasize multi-layered protection and the combined use of waterproofing materials, while simultaneously addressing the roof’s fire safety requirements. Give full consideration to the organic integration of waterproofing and thermal insulation.