Corners and openings in sandwich panel walls: when to specify bespoke flashings

Compare the design dimensions with the prepared opening. Check straightness, diagonals and frame position before fabrication. Custom flashings should fit the agreed detail, not hide an unresolved discrepancy in the steelwork. Resolve significant deviations before ordering the complete set of trims.

The type of corner determines the bend direction and which face is visible. A section that looks right in outline may show the back of the sheet after installation. Mark the exposed face, both leg dimensions and the actual angle if the corner is not square.

Cover the intended joint without restraining movement that the facings need. A long vertical joint may need a different solution from a short return beside a door. Do not replace a folded three-dimensional trim with a flat strip without checking what the joint must do.

The head flashing works with the cladding above to keep runoff out of the joint. A sill or drip flashing below needs a clear discharge edge. Jamb pieces join the two zones. Detail their ends as carefully as the straight runs: an open corner can let water track behind an otherwise sound surround.

Set the sequence of assembly by the runoff direction and the frame detail, not just ease of access. Arrange laps accordingly. The metal trims do not replace specified tapes and seals. Show each layer in section before the surround hides the panel edges.

The structural frame around the opening and the door or window fixings must carry their design loads independently of the decorative trim. The same distinction applies at the wall base, where a starter support and a thin cover strip serve different purposes. Several folds and a stiff appearance are no proof of capacity.

Ask the fabricator to confirm that a special section can be folded as drawn. Structural parts also require design checks; manufacturability alone does not establish capacity. State the intended use on the order so a cover is not supplied where the project needs a support or frame member.

Choose galvanised, aluminium-zinc-coated or colour-coated sheet for the location and exposure. If both faces of a reveal are visible, specify the finish of each. A deep recess can expose a return hidden in a front elevation. Marking the fold orientation avoids surprises on site.

Verge trims, ridge caps, gutter aprons and chimney flashings can share a colour scheme without requiring identical materials. For an interior subject to washdown or deposits, also check compatibility between the coating and the cleaning agents in use.

Give every flashing type a reference linked to the drawing and installation position. Add the grid line or opening number on larger buildings to distinguish similar and mirrored pieces. Before proceeding with repetitive work, inspect a complete first opening, including its seals.

Inspect ends, fixings, cut panel edges and drainage paths. Photograph the layers that will be hidden, then remove swarf and waste after installation. With the parts and photos linked to the drawings, maintenance staff can identify the precise corner or opening on later inspections.