VCONST02720 - Zero-rating the construction of buildings: services excluded from zero rating: design and build
Architectural or design services supplied as part of a design and build contract can be treated as part of the zero-rated supply of construction services.
A typical design and build contract will require the contractor to complete the design for the works and complete the construction of the works.
In such circumstances HM Revenue & Customs (HMRC) sees the design element as a cost component of the construction and not as a separate supply of architectural services which would be liable to VAT at the standard rate.