Stage 4: Technical design

(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.

Wind Tunnel Testing1

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 on 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 during this period.

Isotherm Model1

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.

Stage4During 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.