Technical Portal for Sustainable Architecture
Concealed fixing engineering: structural safety and large-format management in ventilated facades
The evolution of contemporary architecture is pushing the use of seamless cladding and large surfaces (XL panels and larger). While eliminating visual constraints enhances the design of the building envelope, it also introduces complex static and dynamic challenges.
In over 30 years of building envelope engineering, VM Group has developed concealed fastening systems that combine a purist aesthetic with the most stringent structural safety standards, eliminating the risk of detachment and localized breakage.
The limits of traditional poses and the physics of large formats
For large slabs (porcelain stoneware, HPL, or stone), traditional direct-glue installation on a masonry substrate presents insurmountable structural limitations. Cladding materials and the building's load-bearing structures have different coefficients of linear thermal expansion. When the surfaces are large, differential movements caused by seasonal and daily temperature variations generate immense parasitic stresses at the bonding interface.
In traditional facades, this stress cuts through the rigid adhesive layer, causing cracks and, in the worst case, sudden detachment of the slab.
The VM Group ventilated facade system solves this critical issue at its root: the external cladding is completely decoupled from the load-bearing structure. The substructure absorbs the building's deformations, leaving the slabs free to move and breathe within their technical joints.
Anatomy of the VM Group Hybrid Disappearing System
To ensure maximum stability on large formats, VM Group uses cutting-edge structural chemical fastening systems, integrating silent mechanical restraints only where engineering challenges require it.
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Structural Chemical Fastening (Standard Configuration): The back of the sheet is secured to the aluminum alloy profiles using beads of permanently elastic structural adhesive (MS Polymer or high-modulus polyurethane) coupled with technical double-sided tapes. This system is ideal and widely certified for the vast majority of applications: it distributes loads evenly along the entire length of the profile, absorbs vibrations, and eliminates the stress concentrations typical of point fastenings.
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Mechanical Integration (Hybrid System for High Heights or Specification Requirements): The chemical system can be transformed into a hybrid system by inserting hidden mechanical anchors on the back of the sheet (undercut systems with a truncated conical section, keep-nut bushings, or kerf grooves). This option is not a standard requirement, but is implemented by VM Group as a necessary solution in the case of significant building heights (strong wind loads) or at the explicit request of the designer and construction management, offering a geometric relief constraint that is invisible from the outside.
The Chemical Component (Elastic Adhesion)
The back of the sheet is attached to the aluminum alloy profiles using a system of double-sided technical tapes and beads of permanently elastic structural adhesive (MS Polymer or high-modulus polyurethane).
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Function: The adhesive distributes loads evenly along the entire length of the profile, eliminating the stress concentrations typical of point fastenings. Furthermore, its elasticity acts as a shock absorber against vibrations and micro-settlements.
The Mechanical Component (Hidden Geometric Constraint)
To support chemical fixing, mechanical systems invisible from the outside are integrated, chosen based on the material:
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Undercut Systems (Keil or certified equivalents): For porcelain stoneware and natural stone, countersunk holes with a truncated cone section are drilled on the back of the slab. A geometrically expanding anchor is inserted into the hole, which anchors without generating internal stresses in the material.
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Keep-Nut Systems: Mechanical press-fit inserts with flexible crowns that anchor into the back of even thin materials.
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Kerf Systems: Continuous or partial milling along the thickness of the slab's edge, into which concealed stainless steel brackets are inserted.
These mechanical anchors on the back of the slab are then clamped directly to the vertical uprights of the substructure. In this way, even in the extraordinary event of chemical failure, the mechanical constraint geometrically prevents the slab from falling.
Active prevention of slab detachment and load calculation
Every single XL panel installed by VM Group is not simply "installed," but is an engineered element. The density of the mechanical fastenings on the back and the spacing of the aluminum profiles are analytically calculated during the detailed design phase based on three stringent variables:
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Local wind load: Calculated in accordance with NTC (Technical Construction Standards), considering the building's height and its ground roughness class.
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Material self-weight: This affects the shear and bending forces on the back anchors.
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Seismic forces: The hybrid system's decoupling ensures that, in the event of an earthquake, inter-story movements of the building's skeleton are not transferred to the cladding, eliminating the risk of brittle fractures and cascading detachments.
All the components used by VM Group are covered by European Technical Assessments (ETAs) and the structural adhesive application processes follow strict temperature and humidity control protocols on site or in the pre-assembly plant.
The advantages for the Designer and the Client
Choosing the VM Group engineered concealed system offers concrete certainties:
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Absolute Freedom of Expression: Seamless surfaces, clean joints, and the absence of exposed clips or brackets, preserving the aesthetic value of the architectural project.
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Certified Safety: Dual safety (chemical + mechanical) statically calculated to last beyond the building's useful life (over 50 years).
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Improved Acoustic Insulation: The interposition of the elastic structural adhesive dampens impact and wind sound frequencies, breaking down acoustic bridges between the exterior cladding and the structure.
