Roof windows are often an attractive option for homeowners due to their ability to fit into the line of the roof; thus not necessitating any restructuring of the roof itself. The installation of such windows will provide the loft space with substantial light. A roof window conversion can often be completed under permitted development rights and will not require planning permission, although they will always require building regulation approval (UK).
A dormer is a window-featured extension of the roof, usually installed to provide more space and headroom within the loft, in addition to improved staircase access. Dormers are also popular due to the aesthetic enhancement to a property that they provide. In the UK, the installation of a dormer is subject to planning permission requirements from the local authorities only when certain rules aren’t met. Most dormer conversions come under permitted development.