Installing solar panels on a roof? Read the roof covering instructions first

Check the coating, joints, flashings and substrate. If the roof needs repairs, plan them before the modules are installed. A later repair may mean removing part of the array. Allow for access to chimneys, roof outlets, gutters and inspection points. If records are missing, the profile designation cannot be reliably identified from a photograph alone. The covering may need to be measured and identified on site before a mounting system is selected and alterations are assessed.

Read the roof covering instructions together with the mounting system documentation. Check the substrate, sheet thickness, permitted fixing area and anchorage method. The screw count on a neighbouring building is no basis for the design. Fixing spacing depends in part on wind loads, roof geometry and the zones near the edges of the roof.

Some systems transfer loads through the sheeting. Others use brackets anchored to the supporting structure. Confirm that the proposed system suits the application and assess the existing fixings holding the roof covering in place. Even new sheets need to be checked for adequate load-bearing capacity before an array is installed.

A roof penetration must remain watertight as temperatures change and the structure moves. Use the specified sealing washer and connection detail. Applying an arbitrary sealant over a screw cannot take their place. Follow the instructions for gasket selection, compression and bracket geometry. Excessive tightening may deform components and impair the seal.

With sandwich panels, protect the core and maintain continuity of the seals. In a built-up roof, pay attention to penetrations through the airtight layer on the inside. Hidden leaks can allow moisture into the insulation. A roof that stays dry in the first shower still needs its connections checked.

Use tools and cutting methods approved by the supplier for coated sheet. Hot swarf can damage the coating, and metal particles left on the roof can become corrosion sites. Remove drill swarf as instructed. Protect the surface from sharp edges and avoid dragging mounting rails across the roof.

Check that materials touching the roof covering are compatible. Contact between different metals, contamination and trapped water can accelerate corrosion. Use cleaning agents suitable for the coating. If damage occurs, agree on a repair method before handover. A scratch remains vulnerable to corrosion even when a module covers it.

Warranty terms may specify permitted mounting systems, prior approval and inspection requirements. Read the warranty for the product and coating actually purchased. A general web page may differ from the terms that applied on the purchase date. Check which edition of the installation instructions was used for the design.

If the documents do not cover a particular connection, request written clarification from the warranty provider and the mounting supplier. Include the covering specification, a drawing of the bracket and the proposed anchorage. A reply addressing those details is more informative than a general assurance. The installer’s own statement cannot extend another party’s warranty.

Keep the module layout, fixing specifications, instructions and handover record. Photograph connections before they are covered. Record who is responsible for the roof, the PV installation and the interface between them. Agree how leaks should be reported and how service personnel can reach the roof. These records will help trace the cause of a later fault.

Use the records to set inspection dates, identify the connections to check and specify permitted maintenance methods. The long-term performance of a rooftop PV installation depends on a mounting design compatible with the covering, careful installation and ongoing maintenance.