How to cut a sandwich panel and protect the exposed edge

A panel can be easy to cut even where an alteration would compromise the wall. Check whether the proposed change is permissible. In an existing building, locate cables, pipes and concealed parts on the far side. Access to both faces makes it easier to plan and control the work safely.

Follow the panel manufacturer’s instructions for tools that cut without heat damage to the coating. Depending on the work, you may need a dedicated panel saw, a saw with a suitable blade or a tool for cutting the sheet facing alone. Match the tool to the core thickness and the guidance for that particular product.

Avoid an angle grinder with an abrasive disc. It heats the cut edge and scatters hot particles that can damage both the paint finish and the underlying metallic coating. Sparks pose a further risk with combustible cores. Coating damage can occur even if there are no visible scorch marks.

Rest the panel on stable supports and support the offcut so that its own weight cannot tear the facing away. Position the supports to suit the panel length and the direction of the cut. Check that every contact surface is clean. Even a metal shaving or a small stone beneath the facing can scratch it.

Mark out the cut from the finished detail. Allow space for flashings, installation clearance and seals as required. Shield the surrounding area from swarf. Follow the tool and material instructions when selecting eye and hand protection and any additional protection needed for dust.

Before cutting, set aside a place for sharp sheet-metal scraps and larger pieces of panel. Keep them clear of walkways and away from the finished façade. Remove loose core material and swarf in the way specified for the material and the work. Clean the supports between cuts so debris from one opening cannot scratch the next panel. This is especially important when a run of identical openings is being cut.

Use the blade, cutting speed and feed appropriate to the tool and panel. A worn blade may snag the sheet and wander off the marked line. If the tool struggles, check the selection and condition of the blade before applying more force.

After cutting, examine both facings and the core. Look for separation, chipped areas and distortion around the corners. If the blade has overshot a corner or left an unintended sharp notch, check the specified detail to see what correction is needed. Assess any damage to the bond before covering the edge with trim.

Collect metal shavings from both faces of the panel, the surface beneath it and all joints. Stray particles can rust on the coating and leave stains. Clean without scratching the finish. Rubbing the particles across it with a stiff brush can make the damage worse.

Prepare and protect the edge as specified for the type of facing. Fit the intended closure over the exposed core. Touch-up paint on the steel protects only the treated area. To seal the entire perimeter, use the specified arrangement of flashings and seals and select the sealant to suit that detail.

Once the opening is finished, check the frame fixings, the seals and the path for water to drain. On a façade, inspect the junction after wind-driven rain. In a room that is washed down, observe it during routine cleaning. Check how the detail performs under the conditions it actually faces.

Update the building records and keep photographs taken before the trim went on. A future repairer will then know where the panel ends and how the opening is supported. Taking care with the cut and finish now costs less than opening the junction again months later to deal with leaks or corrosion.