The five victorious schemes were selected from 109 entries, which were submitted by architects in the south of England.
Run by RIBA South East and RIBA South, and sponsored by Ibstock Brick, the Ibstock Downland Prize is awarded to architects for projects under £750,000 total cost.
The five winners are:
Overall winner: Lap Chan, Morgan Carn Partnership, Brighton, for a pair of villas which are a new take on the traditional semi, in a conservation area of Lewes.
Winner, domestic: Simon Cottell, CCD Architects, St Peter Port, for a new garden room wrapped around a Victorian house, near St Martin, Guernsey.
Winner, small project: Jeremy Spratley, Spratley Architects, Henley-on-Thames, for a refurbishment and extension of a 1960s estate house, Marlow Bottom, Bucks.
Winner, historic context: Damien Blower with Robert Blower, Stedman Blower, Farnham, for the seamless joining of two parts of a 17th century farmhouse near Binsted, Hants.
Winner, commercial: Douglas Riach, Riach Architects, Oxford, for an office and apartments scheme on the site of a butcher's shop in Headington, Oxon.
David Falla, Chairman of RIBA South East, said: 'The clients revealed their dream projects to their architects; and their architects translated those dreams into bricks and mortar.
'It was the mutual trust and understanding between architect and client that created innovative, exciting buildings. It is particularly good, too, to acknowledge that the planning authorities shared their vision.
'Now is an excellent time to commission smaller buildings in the South East,' he added.