Skylight and rooflight questions, answered
One question, one clear answer. Find yours in the list, or ask us about your own roof.
Start hereSkylight or Rooflight: What's the Difference?The two words mostly overlap. Where a real difference exists: trade usage, product names and the Part L limits.5 min readChoosing and planning
How Long Does It Take to Fit a Skylight?Fitting is the short part. What decides the time: roof type, a new opening or a swap, made-to-measure lead time, weather and the finishing inside.5 min read
When Should a Skylight Be Replaced?The signs that point to replacement, which are glazing, frame and flashing faults, and what a survey checks before recommending a new unit.5 min read
Roof lanterns
Do Roof Lanterns Need Building Regulations?Yes, almost always: a lantern alters the roof structure and its energy performance. Structure, Part L, safety glazing, ventilation and who files the notification.5 min read
How Is a Roof Lantern Kept Watertight?A lantern stays dry through layers, not one seal: a raised upstand, a membrane dressed up it, a sealed base, drained bars and a flat roof that falls.6 min read
Can a Roof Lantern Go on an Existing Flat Roof?Usually yes. The roof must carry the weight, the opening must be framed, the covering must be sound enough to join, and the fall must drain.6 min read
Flat roof rooflights
What Pitch Does a Flat Rooflight Need?A flat rooflight needs a roof that drains, a level kerb and glass with its own slight slope. What the fall does, and what we check.5 min read
Can a Rooflight Go in a Felt or Rubber Roof?Rooflights fit felt and EPDM roofs. How the covering is joined to the kerb, when the roof is too tired, and what we check at survey.5 min read
How Big Can a Flat Rooflight Be?What sets the largest flat rooflight: glass weight, the roof structure, joint positions, safety glass and energy limits.5 min read
Roof windows
Can a Roof Window Be a Fire Escape?When a roof window counts as escape, the 4.5 m height limit, the clear opening sizes and why most two-storey lofts need a stair.5 min read
What Size Roof Window Do I Need?How to size a roof window: read the size code, work within the rafter gap, allow for escape and glazing, and see the room before you decide.5 min read
Can Roof Windows Go in a Low-Pitch Roof?Low-pitch roofs and roof windows: the maker's minimum pitch, why water is the issue, special flashings and the flat rooflight alternative.5 min read
VELUX windows
Can a VELUX Window Be Replaced From Inside?Sometimes yes. It depends on whether the flashing can stay, whether the new window matches the old size and what the surround looks like.5 min read
How Do I Find My VELUX Window Size?Open the sash and look for the data plate on the frame. Failing that, measure the outer frame and match it to the nearest standard code.5 min read
Can Blinds Be Added to a VELUX Window?Yes. Blinds are made to fit each window size and series, and the choice depends on whether you want darkness, glare control or heat retention.5 min read
Electric & opening rooflights
What Happens to an Electric Rooflight in a Power Cut?An electric opening rooflight normally stays in its current position when power fails. What manual release and battery backup can do about it.6 min read
Does an Electric Rooflight Need an Electrician?The mains side of an electric opening rooflight is electrical work under Part P. Who does what, what gets certified and how to plan the cable.6 min read
Can an Opening Rooflight Ventilate a Bathroom?An opening rooflight clears steam well, but a bathroom usually still needs an extract fan. What the rules expect, and where to place the vent.6 min read
Energy efficient rooflights
Double or Triple Glazed Rooflight?Double glazing meets the Part L limit and keeps more light. Triple adds warmth at the cost of weight and brightness. When each suits.5 min read
Does a Rooflight Make a Room Cold?Glass loses more heat than roof, but a modern unit fitted well adds little cold. What causes the chill and how to avoid it.5 min read
What Is Solar Control Glass?Glass with a coating that limits solar heat. What it does, what it costs in light and winter warmth, and when a rooflight needs it.5 min read
Misted rooflight replacement
Can Just the Glass in a Rooflight Be Replaced?Sometimes, when the frame is sound and the glass is a separate unit. How we tell, and why many rooflights go as a whole.5 min read
Does a Misted Rooflight Need Replacing Straight Away?No emergency, but no recovery either. What waiting costs, and the signs that mean acting sooner.5 min read
Will Replacing a Rooflight Mark the Ceiling?What is protected, what can be disturbed, and what a like-for-like swap leaves around the opening.6 min read
Walk-on rooflights
How Much Weight Can a Walk-On Rooflight Take?There is no single figure. Each unit is designed for a stated load, and the answer depends on the glass, the span and the support under it.5 min read
Are Walk-On Rooflights Slippery?Smooth glass is, especially wet. A proper walk-on rooflight carries an anti-slip finish, and the choice of finish is a trade-off with light and cleaning.5 min read
Do Walk-On Rooflights Need Building Regulations?Usually yes. Cutting a new opening alters structure, insulation and safety, and replacing glazing is controlled work too. Planning is a separate check.5 min read
Conservation rooflights
Do I Need Consent for a Conservation Rooflight?Which jobs need listed building consent, planning permission or Building Regulations approval, and which fit permitted development.6 min read
Do Conservation Rooflights Sit Flush?Nearly flush, not perfectly flush: how close the glass sits to the tiles, why a small step remains and how it is sealed.5 min read
Can Conservation Rooflights Open?Fixed or opening: how an opening conservation rooflight works, when it counts as an escape window and what the planning rules say.5 min read
Sun tunnels
How Much Light Does a Sun Tunnel Give?A sun tunnel gives a soft, even pool of daylight. How much depends on tube width, length, bends and what shades the dome.5 min read
Can a Sun Tunnel Run Through a Loft?Yes, that is the usual route. What decides it is the clear path through the roof void, the roof structure, and how the cold section is insulated.5 min read
Does a Sun Tunnel Need Planning Permission?Usually not for a house, under permitted development. Flats, listed buildings, Article 4 areas and Building Regulations are the exceptions to check.5 min read
Each answer is short on purpose. It gives you the fact, the reason and, where it matters, the next step. If a question needs more room, the answer links to a longer page.
Common starting points are the difference between a skylight and a rooflight, whether Building Regulations apply, how long a job takes and when a rooflight needs to be replaced. Questions about a particular product sit within that product's service page, such as roof lanterns.
If your question is about your own house, an answer in general terms can only go so far. A roof's covering, structure and position change the advice, which is why we survey before we quote. Send us a photo and we will tell you what we see.