The facade package — including cladding, curtain walling, windows and entrance systems — is frequently the largest subcontract on commercial and higher-density residential projects. It is also the most complex to coordinate, combining architectural intent, structural interface, waterproofing, thermal compliance and fire performance. Early engagement with your specialist glazing and cladding contractor is one of the highest-value actions a main contractor or developer can take on any project.
Aluminium Rainscreen Cladding
Rainscreen cladding uses an outer aluminium panel layer separated from the building's insulated structure by a ventilated cavity. The cavity allows water that penetrates the outer panel to drain away harmlessly, making the system highly effective in the UK's wet climate. The structural substrate behind the rainscreen — whether a structural framing system (SFS) or the primary structure — must be designed to transfer facade loads safely.
Aluminium rainscreen panels are available in a wide range of profiles — flat, cassette, hook-on, secret-fix — and finishes including powder coat, anodised, mill finish and Pvdf coating. Panel sizes can typically span 1.2m to 3.6m between fixings depending on panel thickness and wind load zone.
Unitised Facade Systems
Unitised facade systems are factory-assembled panel units — typically one-floor-by-one-bay — that are transported to site and craned into position floor by floor. Each unit interlocks with adjacent panels via pressure-equalised joints. The key advantages over stick-system curtain walling are programme speed (installation can follow the structure by just two to three floors), reduced site labour, and significantly better quality control through factory fabrication.
Unitised systems are the preferred solution for projects with tight programmes, large repetitive facade grids, or where site access is restricted. The higher fabrication cost is typically recovered through reduced installation time and lower site preliminaries.
Post-Grenfell Compliance for External Wall Systems
Since the Grenfell Tower fire, the specification of external wall systems has been fundamentally changed by the Building Safety Act 2022 and updates to Approved Document B. For buildings over 18m, combustible materials in the external wall are prohibited (subject to limited exemptions). Aluminium rainscreen cladding with a suitable core material (e.g., A2-s1,d0 or A1 classified panels) and non-combustible insulation is compliant. The ACM cladding implicated in the Grenfell fire has been removed from new projects.
- For buildings over 18m: all materials in the external wall must achieve A2-s1,d0 or better under EN 13501-1
- For buildings 11m–18m: Regulation 7 applies; limited combustible materials may be permitted with justification
- EWS1 forms (for mortgage lenders) require the external wall system to be assessed by a suitably qualified professional
- NHBC, BRE and LABC all publish guidance on compliant cladding specifications
Programme and Procurement Advice
- Engage a specialist facade contractor at RIBA Stage 3 — earlier engagement reduces design risk and improves programme certainty
- Allow minimum 16–24 weeks for unitised system fabrication and delivery from order
- Rainscreen systems typically require 8–12 weeks lead time depending on panel type and finish
- Structural framing systems (SFS) should be coordinated with the groundworks and frame programme — early information saves cost
- Include a mock-up requirement in the specification — this resolves interface issues before production commences
BDF Architectural delivers aluminium rainscreen, unitised facades and structural framing systems for commercial and residential projects across London and the UK. Contact us at RIBA Stage 2 or 3 for technical support.
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