Aluminum Roof Panel Installation Checklist for Overseas Projects: What to Verify Before Work Starts

When the contractor is local and the panels are imported from 8,000km away, installation errors become expensive problems. There’s no factory rep you can call for a same-day site visit. The crew interprets the drawings as best they can, and you find out about the problem when water comes in at month 18. This checklist is for buyers and project managers who need to get it right the first time.

Before panels arrive: what to specify in the contract

Purlin spacing must be in the structural drawings and confirmed against the panel span capacity before steel erection starts. For 0.7mm face sheet Great Wall panels: maximum 1,200mm purlin spacing at standard wind loads. For 1.0mm face sheet: 1,500mm. If your structural engineer has specified purlins at 1,800mm centres for cost reasons, and you’re installing 0.7mm panels, that combination will fail under the first significant windstorm.

Roof slope needs to be confirmed at minimum 5° (approximately 1:12 pitch) for standard panel joints. Below 5°, capillary action can draw water backward through the lap joint against the drainage direction. This is not a sealant question — it’s a geometry question. A slope change requires structural modification, not a caulk gun.

Ridge and eave details need to be designed before panels are ordered, not improvised on site. The standard ridge cap, eave closure piece, and gutter connection are not complex — but they need to be specified and included in the order. Improvised site-fabricated details with sheet metal offcuts are how roofs fail at their perimeters.

On delivery: what to verify before installation starts

Check panel lengths against the cutting list. Panels should arrive at the ordered lengths — but measure 10% of panels in each delivery batch. A 5mm length error on a 6m panel compounds across a row and causes the ridge cap to not fit correctly.

Check the panel profile for transit damage. Great Wall panels are bundled face-to-face in the factory, but a container that shifts in rough seas can bend the rib edges at the bundle ends. Bent rib edges don’t lock correctly into adjacent panels. A rib edge that’s bent more than 3mm needs to be either straightened carefully (cold, not heated) or set aside — trying to force-lock a deformed edge compromises the weathertight joint.

Confirm fastener specification matches the site environment. If the project is coastal and the BOM says galvanised screws, replace with 316 stainless before installation starts. Retrofitting fasteners after the roof is on means drilling out every fixed point — which is a disaster. The upgrade cost is minor at procurement; it’s a major remediation at year 3.

The five installation mistakes that cause most failures

Wrong lap direction. Panels must be installed so that the weather-face lap runs away from the prevailing wind direction. Installing upwind means wind-driven rain is pushed directly into the lap joint. The installation drawing shows the correct orientation — follow it, even when the crew thinks they know better.

Over-torquing fasteners. The EPDM washer compresses to seal the fastener penetration. If the screw is driven until the washer deforms visibly beyond the screw head diameter, the washer is damaged and the seal is compromised. Hand-tight plus quarter-turn is the right torque for EPDM-backed screws. Power driver with torque-limiting bit is the right tool.

Missing end laps sealant. Where panels are joined end-to-end along the slope (on runs longer than 12m), the end lap needs two beads of neutral-cure silicone applied before the upper panel is placed. This is often skipped because the crew assumes the overlap itself is weathertight. It is not — end laps are the most common source of leaks on installed roofs.

Cutting panels with abrasive discs. Steel burr from abrasive cutting deposits on the aluminum surface and causes immediate rust staining and accelerated corrosion. Use carbide-tipped circular saw blades or nibblers for panel cutting. Any abrasive-cut edge should be cleared and sealed before installation.

Walking on the panel flat. Foot traffic on the flat of the panel causes oil-canning (permanent surface waviness) and in thin-gauge panels can crack the foam core. All foot traffic during installation must be on the ribs only — specify this to the site foreman before work starts, and check it on the first day.

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