21 St James Mansions, Mount Stuart Square, Cardiff, CF10 5LG

21 St James Mansions is a two-bedroom semi-detached house in Cardiff (CF10 5LG). It has a recorded floor area of 77 m² (around 829 sq ft), construction records dating it to 2003-2006 and council tax band E. At 77 m² this is the 20th smallest of 24 units on EPC record in the building, where floor areas span 39–92 m². The building's EPC ratings span D to B, with this unit at the bottom. The latest certificate (March 2021) shows a D (score 66), on the cusp of jumping into the C band. Earlier certificates rated it C (March 2009); the latest reading is one band lower. Between certificates, lighting went from Poor to Very Good; while roof efficiency dropped from Good to Average and hot-water efficiency dropped from Very Good to Poor. The recommended improvements would push it to C (score 80). Main heating runs on electricity.

It hasn't traded since February 2008, a hold of 18 years that's notably long for the area. That sale landed at the peak of the pre-credit-crunch market, which is a useful reference point when interpreting the price. At 77 m² the property is well over the postcode median (54 m² across 23 EPCs), placing it in the larger end of the local stock. Today's modelled estimate of £172,000 is 16.6% above the 2008 sale price.