Specialist contractors are
defined as those subcontractors who provide a design input as well as undertaking
manufacture and construction. With the exception of some simple window
contracts all building envelope contracts have a design element within
Even a plain wall of stick
construction will have bespoke components designed by the envelope contractor.
Penetrations through the envelope
Most building envelopes are specified using a performance specification. This transfers certain
design resonsibility to the specialist contractor. The specialist contractor will exercise engineering
judgements when interpreting a performance specification; in particular how performance
requirements are to be met. There are many design solutions that may be used to meet a project specification.
Selection of components
The specialist contractor will select the components and materials to be used in the building envelope
unless they are specified prescriptively, for example, the specialist contractor will select the glass type,
operating hardware and so on. They may even select the framing system to be used.
The specialist contractor will produce workshop drawings and site drawings. They will always decide on joint
locations, bracket design and other bespoke elements of the building envelope. They will detail additonal elements
of the building envelope such as brise soleil. It is important that a specialist contractor with appropriate
design skills is employed.