Everything about your roof, explained by the roofer himself

A roof window gives daylight and is a simple, low-maintenance job. A dormer gives standing height and usable floor area, but has considerably more connections that have to stay watertight and more often needs a permit.

Condensation on the inside of the pane is usually a matter of too much moisture and too little airflow, not a defect. Condensation between the panes means the double glazing has failed, and then replacement is the only solution.

A roof window on the rear roof slope is often permit-free if it does not stick out, or hardly sticks out, above the roof surface. At the front, on a listed building, in a protected townscape or in a flat with an owners' association (VvE), different rules apply and an assessment is needed.

Velux and Fakro both supply solid roof windows, and for most homes the difference in quality is not the deciding factor. Where the difference does lie: availability of parts in the long term, the range of accessories and the sizing that suits your roof.

A roof window needs replacing when the glass stays misted on the inside, the frame is soft or rotten, the window sticks or no longer closes, or it has single glazing or old double glazing. Replacing it in the same opening is a straightforward half-day job.