He trained as an architect before entering the WM ministry. He used to tell of the occasion when King George III, at his own request, accompanied him to a class meeting. After ill health forced him to retire in 1810, he practised from Red Lion Square, London and was involved in building a number of chapels in London (including China Terrace, Lambeth (1807-8), Long Lane, Southwark (1808), the first Hinde Street (1810) and Great Queen Street (1817)) as well as in the provinces (e.g. Carver Street, Sheffield (1804) and Waltham Street, Hull). His designs are carefully proportioned and often feature delicately detailed Classical porticos placed centrally on otherwise flat façades. He is listed in the Minutes as a Supernumerary in the London West Circuit from 1810 until 1840; but the absence of any obituary suggests that he may eventually have resigned from the ministry to concentrate on his architectural work. He died on 19 June 1844 and was buried at Wesley's Chapel.
His eldest son, William Wesley Jenkins (died 1864) was also an architect and is said to have won second prize in the competition for Westminster College, Horseferry Road (1854) and the English Wesleyan chapel at Carmarthen (1861-2). He is credited with what 'were considered model chapels, built on one uniform plan,' and modelled externally on Wesley's Chapel, London. Bethel, Rochester (1810) and St. Peter's Street, Canterbury (1812) are examples. In other examples there is some confusion in the sources as to which were designed by father or by son; e.g. Great Queen Street, Hinde Street, Southwark, King's Cross and Lambeth are variously ascribed to each architect, as are Waltham Street, Hull and Carver Street, Sheffield, Walcot, Bath and The Mint, Exeter.
A younger son, John Jenkins (c.1798-1844(?), was a surveyor, a trustee of the first Hinde Street chapel. He had produced a first draft of the chapel, which was developed by his father.