Rainscreen Substructures: Aluminium, Galvanised and Stainless Steel
A rainscreen substructure is a metal framework fixed to the load-bearing wall that holds the cladding away from the insulation, forming the ventilated gap. It consists of brackets, rails, anchors and cladding fixings and is made of aluminium alloys, coated galvanised steel or stainless steel.
The main selection criterion is calculation: the substructure must carry the weight of the cladding and the wind load of the particular building with a margin, must not corrode in service, and must have confirmed compliance with the requirements for facade systems. The choice depends on the cladding, building height, climate and substrate. All articles on the topic are in the section Ventilated rainscreen facades.
Types of substructure
Rainscreen substructures are classified by several features.
By rail layout:
• vertical — brackets and vertical rails; the most common layout for porcelain stoneware and panels;
• horizontal — rails run horizontally; used for certain cladding types;
• cross (slab-to-slab) — vertical and horizontal profiles; lets the system bear on the floor slabs when the wall between them is weak (for example, aerated concrete infill in a frame building).
By cladding fixing: visible (clips, rivets) and concealed (agraffes, undercut anchors, cast-in fixings in panels, adhesive systems covered by a technical certificate).
By material: aluminium, galvanised steel with polymer coating, stainless steel, and combinations.
The market offers systems from various manufacturers — among the well-known brands people often search for are Grand Line, Metall Profil, Hilti and others. Each system has its own range of brackets, profiles and fixings and its own scope of application confirmed by documents. Elements of different systems must not be mixed: calculations and tests are carried out for a specific kit. Angles, brackets and fixings are selected only from the range of the chosen system.
A porcelain stoneware ventilated facade without a substructure does not exist: cladding glued directly to the wall or insulation is a different construction, with no ventilated gap and with its own limitations.
Materials
The substructure material determines weight, corrosion resistance and cost.
| Material | Pros | Limitations |
|---|---|---|
| Aluminium alloys | Low weight, resistance to atmospheric corrosion, precise profile geometry | Greater thermal movement, lower melting point — important for fire safety; thermal expansion must be accommodated |
| Galvanised steel with polymer coating | High strength, lower cost, better behaviour when heated | Corrosion where the coating is damaged, at cuts and holes; heavier |
| Stainless steel | High strength and corrosion resistance, fire resistance | Highest cost, harder to work |
Combined solutions are common: stainless steel brackets and fixings with aluminium or galvanised rails. Stainless steel washers, rivets and anchors reduce the risk of corrosion at the most heavily loaded points.
Contact between dissimilar metals without isolating pads must be avoided — it causes galvanic corrosion. Exact profile properties and permissible loads are given in the system manufacturer's documentation.
Load calculation
A substructure is selected by calculation, not by analogy with the building next door. The calculation is performed by the designer based on data about the building and the system.
What is taken into account:
• self-weight of the cladding — porcelain stoneware, GFRC and natural stone give different mass per square metre;
• wind load — depends on the wind zone, building height and terrain type; it is higher at corners and parapets, so bracket spacing is reduced there;
• ice and seismic loads — in the relevant zones;
• thermal movement — especially for aluminium, accommodated by sliding fixings and breaks in the rails;
• substrate capacity — anchors are selected for the wall material and verified by on-site pull-out tests.
The result of the calculation is the spacing of brackets and rails, the type and number of anchors, and profile sections for each facade zone. Design loads are defined by the current Russian code of practice on loads and actions.
Certification
Facade systems are structures on which people's safety depends, so the use of a substructure must be supported by documents. A system usually has:
• a technical certificate or equivalent document confirming the system's suitability for use in construction, with its scope and limitations;
• fire test results for the complete facade system with specific cladding and insulation, with the fire hazard class of the construction;
• a technical solutions manual — details, schemes, component range;
• certificates and data sheets for profiles, fixings and anchors.
Importantly, the documents cover the system as a whole: replacing the cladding, insulation or substructure elements with ones not covered by the documents can take the facade outside its confirmed scope of application. At the selection stage it is worth checking that the technical certificate is valid and covers the required cladding type, building height and fire hazard class of the building.
Choosing by cladding
Matching the substructure to the cladding is the main task of rainscreen facade design.
| Cladding | Typical substructure | Features |
|---|---|---|
| Porcelain stoneware | Vertical, aluminium or galvanised steel, clips or concealed fixing | Low weight, standard solutions |
| Glass fibre reinforced concrete (GFRC) | Reinforced, fixed via the panels' cast-in fixings | Large and three-dimensional panels, custom details for decor |
| Natural stone | Reinforced, often steel or with stainless steel clips | Heavy, reduced bracket spacing |
| Fibre cement, metal cassettes | Light vertical or horizontal | Minimal load |
For GFRC panels that combine cladding and decor (cornices, pilasters, window surrounds), the substructure is designed together with the division of the facade into products: the positions of the cast-in fixings in the panels and of the brackets must coincide. TECHNOFORMA carries out design, insulation, rainscreen substructure installation and cladding in GFRC, natural stone and porcelain stoneware with its own resources.
Examples on TECHNOFORMA projects
TECHNOFORMA installed a rainscreen facade clad in GFRC and FRONTEK on the RUBLEVO BUSINESS PARK business centre in Moscow (15,000 m² of GFRC, 5,000 m² of FRONTEK). A combination of GFRC and porcelain stoneware on a rainscreen system was used on the Dominanta residential complex in Makhachkala (14,000 m² of GFRC and 13,000 m² of porcelain stoneware, 18 storeys). On both projects the company carried out design and installation.
All projects are in the TECHNOFORMA projects section. The specifics of GFRC panel cladding are covered in the article Rainscreen facade clad in GFRC.
FAQ
What is a rainscreen substructure?
A metal framework of brackets, rails, anchors and fixings that holds the rainscreen cladding away from the insulation.
What substructure is needed for porcelain stoneware?
Usually a vertical aluminium or galvanised steel system with clips or concealed fixing; the spacing is determined by calculation.
Can a porcelain stoneware ventilated facade be built without a substructure?
No. Without a substructure there is no ventilated gap — it would be a different type of facade with its own limitations.
Which is better: an aluminium or a steel substructure?
Aluminium is lighter and does not rust; steel is stronger and behaves better when heated. The choice is made by calculation, cladding and fire safety requirements.
Can elements of different systems be combined?
No, the documents and tests apply to a specific system kit.
