south porch circa early C15, then with north aisle and porch, later all 3 extended to east, finally in the C19, vestry added to north of east end, north porch rebuilt, gable ends partially rebuilt, re-roofed, and new window mullions and tracery inserted.
All windows, except nave west window which is entirely C19, are C15 Perpendicular with C19 Perpendicular style mullions and tracery.
North wall is C15 with original plinth and coved wallplate cornice.
Later C15 ashlar walling to east.
Inner chamfered doorway with 4-centred arch is circa late C15.
Otherwise C15 plinth, walling and outer frames of windows.
Windows enlarged, C15, and mullions and tracery replaced, C19.
Porch doorway is circa early C15 with convex moulded jambs (similar to earlier piers inside church) and 4-centred arch.
Inner doorway is circa late C15 with wide chamfer and stepped stops.
Interior has fine C15 granite arcades (the second tallest in Cornwall) of 5 bays between nave and aisles and 2 bays between chancel and aisles.
Arches are 4-centred over moulded or moulded and carved capitals.
Some memorial windows with coloured glass.
C19 polished marble font to the Reverend John Rogers, father of Canon Saltern Rogers, Vicar of Gwennap 1856-1893
Monuments: West wall (nave) has marble urn within vertical oval to Henry Beauchamp, only son and heir of Joseph Beauchamp, and slate tablet with shaped pediment (over north door) and angels and vine carving by Northey Burnard in 1829 when aged 15.
North wall has monument to James Whitburn, mine agent and marble monument with angel wings to William Henry Tregoning, died 1875 aged 59.
South wall has several marble-monuments to the Williams family including one to Caroline Elizabeth Williams, died 1849 aged 24, of carved figure with urn on pedestal
and marble aedicule with carved sargophogus over tree to Benjamin Sampson Esq. of Tullimaar, died 1840 aged 70.
To east end of south aisle is slate slab to James Pearrowe of St Burian, died 1691.