Pitsea Hall was added to the national list of buildings of special architectural or historic interest on 24 March 1950. It is now listed as Cromwell Manor at Grade II, recognising the importance of the surviving historic building.
Historic England describes Cromwell Manor as a sixteenth- to seventeenth-century timber-framed and plastered house. Although later alterations changed its appearance, parts of the older structure remain visible and help reveal how the building developed over several centuries.
The north side retains particularly interesting historic details. Its upper storey is jettied – projecting slightly beyond the floor below – and rests on a moulded horizontal beam known as a bressumer. Exposed timber framing with brick infill can be seen at ground-floor level, while two original moulded-mullion window openings survive in blocked form.
The south front changed considerably in later centuries. It was refronted in yellow brick during the nineteenth century and two large semi-circular, two-storey bays were added in the twentieth century. The front also includes sash windows and a nineteenth-century doorway with a cornice supported by console brackets.
The tiled roof has five gabled dormers on the south side. A wing extends northwards from the western end of the building. Taken together, the different materials, windows, bays and framing show that Cromwell Manor is not the product of one building campaign: it is a house altered and adapted repeatedly.
Listed status helps recognise and protect the building's special architectural and historic interest. In a part of Basildon transformed dramatically during the twentieth century, the survival of such an old structure is especially significant.