Blaen Senni is situated east of the Afon Senni and minor road running from Heol-Senni to Ystradfellte, 2km south of Heol-Senni. It is a gentry house, largely of the 18th century, of a long-house derivative type plan ' with no direct access between the house and byre. But the northern Hall end of the building may date from the 17th century. Because the house is wide, the staircase beside the stack is unusually spacious. It is a red house with a white byre of 2 storeys and an attic. The house has a pitched slate roof, steeply pitched and descending to ground floor level on the southern side, with a byre with a hipped slate roof. The 17th century newel staircase rises to the full height of the house, with nails used in the construction. The roof trusses are morticed with chisled numbering in Roman. There is a box bed with a separate wardrobe in the parlour. There are ogee stops to the plain chamfers on the beams and moulded cornices around the parlour.
(Sources: H Brooksby, 8 January 1969, NMR Site Files; Brycheiniog 1968-9, Jones and Smith, 'The Houses of Breconshire', p. 58, 61).
Ian Archer, RCAHMW, 7th March 2005