Open-Joint vs Flush-Joint: Choosing an ACP Installation System

Every ACP cladding project starts with one decision that shapes everything downstream — the joint system. Should panels sit flush against each other in a continuous plane (flush-joint, 密拼), or be separated by a deliberate gap (open-joint, 离缝)? The choice affects fabrication, substructure, weather performance, installation speed and how the building will look in ten years.

Flush-joint (密拼): the seamless look

Panels are fabricated with folded edges (-router-grooved and bent, typically 90°) and mounted so adjacent panels touch. The visible face becomes one continuous surface — no gaps, no shadow lines.

• Visual effect: Monolithic, flat, clean. Works best with matte and solid colors.
• Weather sealing: Excellent. The folded edges and closed corners shed water; combined with sealant at key points, the system protects the substructure completely.
• Fabrication: More work per panel — each panel needs four routed and folded edges, and dimensions must be precise. A 2mm error shows up as a visible step.
• Cost: Higher fabrication labor per panel, offset by simpler substructure.
• Best for: Low and mid-rise buildings, column covers, soffits, interior feature walls, signage.

Open-joint (离缝): the rhythm of shadow lines

Panels are cut flat (no folding) and hung on a clip or hanging-ball system, leaving a deliberate 8–16mm gap between panels. The gaps create strong vertical or horizontal shadow lines that give the facade rhythm and scale.

• Visual effect: Structured, architectural, modern. Metallic and mica finishes come alive — the joints break up reflections that would otherwise highlight every panel's slight oil-canning.
• Weather sealing: The gap is intentional, so the weather barrier lives one layer behind: a waterproof membrane or sealed back-pan over the substructure. This must be designed in — it is not optional.
• Fabrication: Much simpler. Flat-cut panels, no folding, and dimensional tolerance is far more forgiving — a 2mm error disappears into the joint.
• Cost: Lower fabrication cost, but you add the cost of the back-pan or membrane layer.
• Best for: High-rise curtain walls, large-format facades, buildings designed around strong lines, ventilated rain-screen systems.

Side-by-side

• Installation speed: Open-joint wins. Flat panels on clips go up 30–40% faster than folded panels that must be aligned to a perfect plane.
• Wind resistance: Flush-joint systems with continuous folded edges generally test stronger. For typhoon regions we recommend flush-joint with stiffeners, or open-joint with verified clip pull-out tests.
• Maintenance: Open-joint gaps collect dust and can streak after rain on light colors. Flush-joint is easier to keep looking new.
• Thermal movement: Aluminum expands. Open joints absorb movement naturally; flush joints need to be engineered with adequate panel counts and fixing flexibility or the seams will zipper open over time.

Our recommendation by project type

• Interior / retail / signage: Flush-joint, PE or HDPE coating. The seamless look sells indoors, and there is no weather to fight.
• Low-rise commercial exterior: Flush-joint with PVDF. Sealed, durable, classic.
• High-rise or large facade with metallic finishes: Open-joint with PVDF or FEVE and a designed weather barrier. The shadow lines flatter metallic colors at scale.
• Coastal / typhoon zones: Either works, but the fixing system matters more than the joint. Ask us for wind-load calculations for your project's zone.

The joint system is decided on the drawing board, not on the scaffold. Changing it after fabrication is nearly impossible — decide it together with your panel supplier, early.