Professional fees cover the design and certification team you need to obtain permission and build lawfully: architect or architectural technologist, structural or civil engineer, assigned certifier, quantity surveyor, BER assessor, site investigation and survey specialists, and your solicitor. Fees are usually quoted as a percentage of construction cost or as a fixed fee for a defined scope.
Under the Building Control (Amendment) Regulations, most new houses need a design certifier and an assigned certifier unless the owner validly opts out of statutory certification for a one-off house. These are defined statutory roles carried out by registered professionals, and they carry a fee separate from design work.
Fees are normally agreed in writing at the outset, setting out the stages covered — feasibility, planning, tender, construction inspection and certification — because a planning-only appointment costs much less than a full service through construction.