Regular roof checks help catch problems before a leak shows up in the attic. For many metal coverings, the manufacturer recommends an inspection at least once a year, and an extra check is justified after a severe gale, hail or chimney work. Maintenance covers the sheet surface, fixings, flashings and drainage, while cleaning frequency should suit the coating and the building surroundings. Even a new covering needs attention: cutting swarf or foil scraps left in the gutter can be washed by rain into places you cannot see, so handover should include clean slopes and clear outlets.

Roof flashings safeguard the edges and junctions of the covering, channelling water away so it cannot get beneath the roof. They include eaves strips, bargeboards, valleys and components around the chimney, matched to the slope and sheet metal. Though sometimes decorative, their shape, laps and fixing determine tightness. The sheet alone is insufficient at terminations, openings and bends – flashing sets a controlled drainage path, even in wind-driven rain.

Flashings close edges and transitions, but above all they guide water. It is worth preparing their list together with the cutting plan for the covering. The length of the roof edge is not yet the number of finished elements. Allowance must be made for laps, separate sections, bends and the installation sequence. Some flashings must be in place before the sheet metal. Mark all eaves, gable edges, ridges and corners. Separately mark roof valleys, chimneys, walls and service penetrations. Each of these lines or obstacles needs its own solution. Not every roof slope has a roof valley, and a mono-pitch roof does not have the same ridge as a duo-pitch roof. The list should correspond to the actual roof form.

A roof valley needs stable support, a continuous underlay and a sufficiently wide drainage path so that water from both slopes can flow freely to the eaves. The most common problems arise from screws placed in the water course, cut pieces that are too narrow, and leaves blocking the valley. Before covering, it is worth checking the geometry where the slopes meet, the evenness of the cut line and the placement of fixings outside the main flow. Also make sure the lower end of the valley discharges water correctly into the gutter and that the membrane beneath the covering has no gaps.

A roofer is responsible above all for the roof covering and the details that protect the building from precipitation, not merely for fixing the sheets. Before work begins, check whether the contract clearly separates carpentry work on the roof structure from roofing work, that is, preparation of the substrate, protective layers and the covering itself. The scope depends on the contract and the team's competence, so one company may carry out both stages, but this should not be assumed without agreement. It is also worth asking who is responsible for assessing the substrate and any consultation with the designer.