A sandwich panel is held in place by one of three methods: self-drilling screws, structural adhesive bonding, or a concealed interlocking clip system. The fixing method is part of the specification, not an afterthought - and each method has its own installation sequence, strengths and failure points.
Self-drilling screws
This is the most common method for roofs and industrial walls. The screw drills through the steel facing, passes through the core, and bites into the purlin behind. A sealing washer under the head seals the hole.
The advantage is speed and strength. Screws give immediate mechanical fixing and are easy to inspect. If a panel is damaged, it can simply be unscrewed and replaced. The disadvantage is that every screw is a potential leak point if the washer is crushed or missing, and metal screws create localized thermal bridges through the insulation.
Installation steps:
Position the panel square to the building line, with the correct eave overhang.
Mark the purlin lines. Screws must hit the centre of the purlin, not the edge.
Drive the screw in the panel valley (not on the rib) using a depth-sensitive screw gun.
Tighten until the washer compresses against the steel - not so tight that it deforms.
Overlap the next panel along the rib to cover the screw heads and seal the joint.
Best for:
Roof panels, industrial walls, high-wind areas, and any project where fast installation and structural strength are the priority.
Notes:
Never over-tighten. A crushed washer is the most common cause of roof leaks.
Use stainless steel screws in coastal or corrosive environments.
Follow the manufacturer's spacing pattern. End fixings need to be closer together than intermediate ones.
Structural adhesive bonding
Instead of mechanical fasteners, the panel is bonded to the frame with structural adhesive. The adhesive forms a continuous connection along the panel length, distributing load evenly rather than concentrating it at screw points.
The advantage is a clean surface with no visible fasteners and no holes for water to enter. The adhesive bond also acts as a thermal break, since there is no metal screw conducting heat through the insulation.
The disadvantage is that the bond depends entirely on surface preparation. Dust, moisture or oil on the steel facing or the frame will weaken the bond. Adhesive also has a curing time, which slows installation, and repairs are difficult - a bonded panel cannot simply be unscrewed and replaced.
Installation steps:
Clean both surfaces. The panel facing and the frame must be dry, dust-free and oil-free.
Apply adhesive in a continuous bead or pattern to the frame.
Press the panel firmly into place, allowing the adhesive to spread at the edges.
Clamp or prop the panel until the adhesive reaches handling strength.
Clean squeezed-out adhesive immediately before it cures.
Best for:
Architectural facades, walls where appearance matters, and applications where drilling is not practical or desired.
Notes:
Surface preparation is everything. Adhesive will not bond to a damp or dusty surface.
Temperature affects curing time. Follow the adhesive manufacturer's limits.
Plan the installation sequence. Once cured, repositioning is impossible.
Concealed interlocking clips
This method uses a shaped edge profile on each panel that locks into the adjacent panel. A clip is fixed to the frame, and the panel edge engages with it, hiding the fixing behind the panel surface.
The advantage is a continuous surface with no exposed holes, giving better weather tightness. The disadvantage is precision - the panels must be aligned accurately, installation is slower, and removing one panel usually requires disengaging the adjacent panels.
Installation steps:
Fix the base clip to the frame at the starting edge, level and aligned.
Engage the first panel onto the clip - this sets the alignment for the whole wall.
Fix the next clip along the free edge of the first panel.
Engage the second panel onto the clip, then repeat in sequence.
Check plumb and level every few panels, not just at the start.
Best for:
Exterior facades, commercial buildings, and projects where a clean, uninterrupted surface is required.
Notes:
Panels must be installed in sequence. You cannot insert one into the middle of a completed run.
The clip must match the panel profile exactly. A clip for a 50mm panel will not fit a 100mm panel.
Check alignment frequently. A slight error at the start compounds down the wall.
