Rooflights, Skylights and New Roof Structures
Where a house already has a rooflight or skylight above a kitchen or extension, a new veranda or glass room roof close by needs to be planned around it rather than in isolation. Shadowing, drainage and structural fixing all come into play.
Shadowing an existing rooflight
A new roof fitted too close to or too high against an existing skylight can reduce the light it originally let in, particularly if the new structure sits above the skylight's sightline to the sky. This is worth checking with a straightforward sketch or site visit before finalising the design.
Drainage between the two roofs
Water running off a new veranda roof shouldn't be directed towards an existing skylight upstand or its surrounding flashing, since that can overwhelm details never designed to take extra flow. Gutters and falls need planning with the existing roof's drainage in mind.
Structural fixing near roof penetrations
Fixing a new frame close to an existing rooflight kerb or flashing needs care to avoid disturbing the seal around it. Where possible, fixing points are kept clear of the rooflight's structural opening rather than tied directly into it.
Solid roofs and lost daylight
If the new structure has a solid insulated roof rather than glazing, it will block more of an existing rooflight's outlook than a glass or polycarbonate roof would, which is a specific reason some customers choose glazing for a new roof positioned near a skylight.
- Map the rooflight's sightline before fixing the new roof height
- Keep new drainage clear of existing flashings
- Consider glazed rather than solid roofing near an existing skylight
Getting it checked on-site
Because every extension and roof shape differs, this is one area where a photograph and a tape measure at survey stage is worth far more than general guidance, particularly on older extensions with non-standard rooflight positions.
Common questions
Will a new veranda roof always block an existing skylight?
Not necessarily — it depends on the height, angle and position of both structures, which is why it's checked individually at survey rather than assumed either way.
Can an existing rooflight be removed if a new roof makes it redundant?
That's a decision for the homeowner and may involve separate building work beyond the veranda itself, so it's worth discussing early if the rooflight will end up shaded.
Does the new roof's drainage need special planning near a skylight?
Yes, falls and gutters should be arranged so runoff doesn't discharge towards an existing rooflight's flashing or upstand.
Should I mention an existing skylight before booking a survey?
Yes, it helps the surveyor plan roof height and drainage correctly from the first visit rather than needing a return trip.
In short
A new veranda or glass room roof positioned near an existing rooflight or skylight needs careful planning around shadowing, drainage and fixing points to avoid compromising either structure.
What to do next
Mention any existing rooflights or skylights when you book your survey.
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