(previous RIBA stages D & E)
These stages are dedicated to developing the key criteria for the façades and identifying the principal performance demands. The individual façade systems are identified and rationalised into main types. We often find that it makes sense to combine types by systems that can be designed and delivered as a single entity, even with quite extensive variations.

We produce a Design Criteria report to capture our proposals for the façade systems, the structure, materials, loading requirements and maintenance. This is carried out as early as possible and circulated in draft as a significant coordination tool.

The structural coordination is essential throughout Design Development as this part of the design progresses to site first. Coordinating movements and tolerances, as well as support and restraint for the façade, is essential during this stage. Coordination with the services strategy and into the detail of the services models is also key. This allows close coordination of the criteria allowing for economic solutions to be identified and agreed between disciplines that fit the architectural intent and achieve the required standards.

Interface see the façade design workshops as a key method of maintaining a well coordinated and achievable design. The interfaces are set out in an initial interface schedule developed at this stage to highlight potential ‘risk spots’ to be actioned. We know that the detailing of the façade should always be informed by its most challenging aspects. We work closely with the architects on each project, reviewing system proposals and details and preparing options and variations to identify the optimum solution. We also work at 1:5 detail level for systems at this stage, but specific details will be at 1:10 or even 1:20 to allow zone and continuity review.

We carry out specific initial engineering analyses during this stage on areas where this is particularly required. This ensures that performance and structural drivers of the design are understood and resolvable at an early stage. Analyses of the Developed Design Stage promotes efficiency whilst preserving the architectural intent.

Our initial engineering analyses include structural and thermal analysis of key areas and determining structural sizes and calculating required U-Values to determine the wall zones needed. We would also carry out a solar study of the buildings to understand the solar incidence on each of the facade and identify the necessity for solar shading on each area and provide the input data needed to evaluate the effectiveness of any solar shading devices at a later stage.

A facade with a complex geometry often has a variety of key construction solutions to be compared. It may be that there is an advantage to present more than one solution, each option presenting different fabrication or installation benefits to the different cladding contractors, but each with its own significant pitfalls. Early identification of these allow close scrutiny and detailed discussion with the team and with cladding contractors.

During the Developed Design Stage interface aim to initiate discussions on material options. We advise at this stage on their suitability by refining the selection with appearance, durability, application and cost being considered and scored. We have developed a system that allows considered, rational selections to be made.

This ‘decision matrix’ allows the team to not only be sure the various aspects are considered and weighted correctly, but captures this information so that it can be easily referred to at later stages should re-appraisal be needed. We carefully review proposed materials with particular attention to durability maintenance and replacement in mind. We include all of these considerations and advise in our Design Criteria report.

We regularly distribute our consolidated information within our Design Criteria report to all related disciplines, requesting particular feedback from specific teams to progress the facade design and maintain the programme. Within this document we also capture the Design Risks. These are documented along with the suggested mitigation opportunities and any ‘close out’ solutions. Being part of the Design Criteria report allows this register to be regularly updated and where necessary carried through the next stage.

(previously RIBA stages E, F, G & H)
Coordination of the façade continues right through Stage 4 (previous RIBA stage E) and on towards tender. The Façade Design Criteria report continues to be used to capture changes and allow the design team to coordinate with the façades. This allows efficient working across the team as well as a lean design and the close out of any design risks that remain.

The interface schedules and façade types mark-ups are updated and expanded to include the key interfaces and all the main types. This invaluable and simple tool facilitates an organised approach to the design of different potential design systems and the cost plan and packaging of the contract for tender. System development and interfaces are prioritised to allow the more complex areas to drive the design, which results in ultimately simpler solutions.

We would expect any wind tunnel testing required to be completed early on in this stage. This will allow our structural analysis to be commenced and for accurate sizing of facade members to be carried out for each of the identified facade types. These are needed to confirm the facade zones and are particularly critical for long span elements in atria or lobbies and the more complex facade types such as pre-stressed cable facades. We are involved in the briefing of the testing and produce an interpretative report to inform the design of the facades.

Thermal analysis is also advanced early in this stage to ensure the design conforms to the required u-values needed for the overall facade and for each element, to be sure that we have a sensible thermal solution. Where difficult interfaces are identified in the interface schedule, the detailing of these can be advanced early to allow our isothermal analysis sufficient time to influence the overall detailing and make sure robust details are developed for tender. The necessary g-values for glazing would be determined and any solar shading devices would be analysed and optimised.

We assist with the materials sampling and review the options available with a keen eye on durability and maintenance as well as price, again using a decision matrix to assist in the decision making process and to capture the outcome. As part of the expansion of the Design Criteria report we would include the material details and the necessary testing regimes.

We also include the areas of any prototype testing required. The development of the facade details is continued through workshops and a review and sketch over process. We recognise the importance of preparing for procurement where it can be crucial to ensure the number of suitable facade contractors who can tender for the job is not compromised by the design.

We resolve the detailing in such a way that it becomes both rational and recognisable to a range of facade contractors. This would ensure that the job is awarded to a facade contractor with both the right factory capacity and design capabilities at the time for the building in question. The interface schedule and facade types mark up are expanded and the interface details developed are also expanded and tested with manufacturers.

During this stage intensive workshops give value and we drive the process forward promptly and allow necessary discussion. At the end of the stage the Design Criteria report has information appended to it and becomes our stage report. This provides an efficient and coordinated reporting system that is already embedded in the working practice of the team.

During Technical Design the issues and opportunities will have been identified aiding the coordination and identification of the suitable cladding contractors. This is a key process for the success of the overall project. With a tight set of information available from the previous stage, this stage concentrates on the “particulars”. Individual interfaces are intensively interrogated without prejudgement to deliver buildable, working solutions that adhere to the design intent.

The Design Criteria report acts as the coordinated base document for the specifications. We make sure that all information from the Design Criteria report is successfully transferred into the specifications, that the materials, testing and acceptance criteria are coherent and sufficient for the project and that the document captures the particular requirements of each individual project.

Once the tender returns are received we carry out a technical tender review which captures the key technical issues and delivers these in a concise and understandable way. This would be accompanied with an issues log which allows the tenderers to respond to questions and any inadequacies identified and allows the team to gain confirmation of items that are unclear. The target is to get an equivalent tender response to allow proper comparison and to close out as many of these areas prior to contract.

(previously RIBA stages K & L)
The cladding contractor design programme is the most important initial document for review. This allows the team to coordinate with the cladding contractor in a meaningful way and assists greatly the smooth development of the design. This is particularly important where multiple cladding contractors are involved and coordination between programmes is essential to avoid delays.

Contractor design workshops are encouraged as a concise method of working. This must include coordination sessions with multiple cladding contractors where present. We aim to establish key designer relationships to allow clear, easy lines of communication for faster, simpler resolution of issues. This is essential for complex detail or engineering issues where direct discussions are necessary to achieve prompt resolution.

The first period for all packages is the system design. This is a critical period and one in which the design team know the project better than the cladding contractor team and need to impart that information into the developing design. The understanding of individual interfaces developed during the earlier stages is essential for the design of the systems to be carried out correctly. We take a very hands on approach to this critical high level design period and expect the contractor to produce details and detailed structural and thermal analysis of the systems proposed. We like to have System design as a stage within the programme so that this can be seen as the milestone that it undoubtedly is.

When this stage is complete, the detailed information is developed for the variations around the project. Our familiarity with the systems allows the review to be carried out efficiently and in detail. We encourage the cladding contractors to prepare schedules of their design works for circulation to the team indicating progress and status. If these are not forthcoming, we have our own simplified versions that allow us to monitor the design process and to assist in the concurrent development of the differing strands of the design.

We encourage early submission of materials information. This is often difficult to achieve as it can limit the commercial opportunities for the cladding contractors. However it does allow essential assessment of the materials for their performance and their compatibility with each other. This is particularly important for items that are the link between cladding packages where compatibility checking takes greater time. Early factory visits to potential key suppliers would be carried out at this time. This would include the glass processor which is always key to the project’s success.

Quality samples submission should then follow and allow the early agreement of the acceptance criteria and make sure that the suppliers are fully aware of the quality requirements of the specification.

Prototype testing is a key stage of the project. With residential buildings it is likely that there will be interfaces between different cladding contractors and this will be the first time they have put their respective designs together. We generally insist on testing within the UK, this may take a little longer for non-UK contractors, but will involve the installers who will be carrying out the installation on site. It is vital that this is used as a learning exercise for construction as well as a confirmation of performance. We always attend the dismantle as this is a key to the assembly and  confirms that the installation was carried out in accordance with the design – or not. We usually provide an initial report on testing. This allows the project to move forward with confidence that the test has passed, whilst the test house completes their report.

Glass processing factories are visited to review the first batch ahead of a large order. An earlier visit can also prove beneficial to be sure that the quality requirements are fully understood and will be adhered to. Key areas are edge quality and the visual acceptance criteria. We have developed a clear methodology for confirming agreement of visual acceptance criteria as this is currently proving to be problematic with many processors due to the variability of bespoke orders.

We would expect to carry out assembly factory visits early on in the production. This allows review of the components being procured as well as the assembly processes and quality. Most importantly, it can catch any errors early on in the production, where they are most likely to occur. Factory visit reports and issues logs are prepared and used as a tool to allow confirmation that the issues are dealt with and closed out promptly.

Pre-installation review of components is carried out during our site visits. These allow close inspection of elements which may only be reviewed much later from the BMU when it is available. We take a proactive approach to site, raising issues as soon as they become apparent to us even on incomplete works. This is to prevent repetitive errors occurring through the works.

Our aim on site is to be part of the delivery team, assisting to maintain the quality and  resolving difficult issues. We understand the complexities of site and the pressures of programme and we engage actively in the resolution of site issues. Our people have all learned that our early intervention and close involvement gives quicker resolution to issues and ultimately delivers our clients a better product.

We schedule all major issues through to close-out and handover. This assists us in closing out the issues and ultimately speeds up the process. Our logging systems prevent us revisiting issues already resolved. We actively support continuity of our staff throughout the project as it gives efficiency to us and to the wider project team.