An alternative to a hip dormer conversion, a hip-to-gable is where the existing roof is extended to meet the gable end and the gable wall is then built up.
A Velux loft conversion is when the new room is formed within the existing loft space meaning that the actual profile of the roof is not altered. Velux roof-lights are installed into the roof slope for natural light and ventilation.
This combines a hip-end dormer and a rear dormer so that the internal space is significantly improved. Typically, a large master bedroom with an en-suite is created although often two good-sized bedrooms and a bathroom are opted for.