In most cases loft conversions can take anywhere between 6-8 weeks, depending on the scale and amount of construction required. However, Velux loft conversions are the easiest to build and can usually constructed within only 4 weeks.
Velux are actually a window manufacturer and are the most commonly used windows in Velux loft conversions. Another way to refer to this build is as a Rooflight loft conversion. This design is comparatively easy to install, with only one of the existing rafters needed to be trimmed out per window. The existing roof structure remains intact and the windows then slot in at an angle to the roof, rather than vertically. Not only is the build time shorter on this style, but due to the minimal alterations, the costs are considerably lower.