Ask someone which room needs a skylight and they say the kitchen, the landing or the box room. Ask them to stand where the light matters and the answer gets smaller and more useful. It is the worktop by the hob. It is the top stair. It is the desk, the basin, the foot of the bed. That one place is where every later decision starts.
This page explains how the spot you use shapes the rooflight above it, in the order we work through it on a survey in Derby and the towns around.
Start here
A room is too big a question
A kitchen can be four metres long and still have one dark corner where the chopping happens. A landing can have a window at one end and a black hole at the other. When the question is "light for the room", the easy answer is a bigger rooflight somewhere in the middle. When the question is "light for this worktop", the answer has a position, a size and a reason.
So we ask you to point. Stand where you cook, read, wash or climb, and we mark it on the floor plan. The rest of the survey is measured from that mark. It costs nothing to do, and it changes what we put on the roof more than almost anything else we learn that day.
The same habit helps you decide before anyone visits. If you are not sure which spot to pick, our guide on where to put a skylight walks through the common places room by room.
Position
The spot sets where the opening goes
Daylight from a rooflight does not drop straight down and stop. It spreads out below the opening, and the light well (the shaft between roof and ceiling) shapes how far. A rooflight placed directly above you gives the strongest light. One placed a metre off to the side still helps, but the brightest patch lands on the floor beside you rather than on the page, the board or the basin.
That is why a rooflight dropped into the middle of a room for neatness can leave the real spot dim. Our job is to find where the opening can sit so the light falls where you stand, then check that the roof allows it. Rafters, purlins, a chimney stack or a valley can all push the opening a little. When they do, we tell you what moves and what it does to the light, before you agree anything.
Why the roof gets a vote
The roof is not a blank sheet. A pitched roof has timbers at set intervals, and cutting one means framing around it with trimmers. A flat roof has joists running one way. Either can take an opening where you need it, and we plan the framing at the survey rather than discovering it on the day.
What gets marked at the survey
- Your spot
- pencilled onto the plan
- Ceiling height above it
- measured at that mark
- Roof timbers overhead
- positions checked from the loft
- Obstructions
- stacks, valleys, services
- Which way the roof faces
- noted for glare and warmth
Size
How the spot sets the size
Size follows from what you do in the spot, not only from the floor area around it. Reading a recipe at a worktop needs steady, even light across a small area. A hallway needs enough light to see the stair edge clearly. A bathroom basin needs light on a face. None of those asks for a huge opening, and a huge opening brings its own costs in heat gain, in heat loss and in the framing around it.
Where one is needed, we work from the spot outward. Start with how far the room sits below the roof, because a taller space can take light from a smaller opening before it fades. A shallow light well from a flat ceiling lets the glass do more with less. A long, deep shaft loses some of the light on its walls, so the opening may need to grow, or the shaft may need splaying and a pale finish.
We would rather tell you a smaller unit will do the job than sell a bigger one that leaves the spot no brighter. If a second unit would serve two spots better than one large one, we say that too.
One big opening or two smaller ones
One larger rooflight
- One cut in the roof
- Even light over a wide area
- Works when spots sit close together
- More glass to manage in summer
Two smaller rooflights
- Light lands on each spot
- Suits spots far apart
- Two openings to frame
- Easier to shade one at a time
Type
How the spot picks the type of rooflight
Once the position and size are settled, the type follows from the roof and from what the spot asks of the glass. These are the questions we ask, and the types they point to.
Is the roof pitched or flat?
On a pitched roof the usual answer is a roof window, fitted into the pitch. Many people think first of a VELUX window, which is one well-known make of roof window and often a sensible choice. Flat roofs suit flat rooflights, lanterns or walk-on units. If the roof is flat and the room below is an extension, a roof lantern can give height and light together. If a flat roof only needs a plain opening, flat roof rooflights are the direct fit.
Can you reach it?
A rooflight over a stair or above a high ceiling is out of arm's reach. An electric opening rooflight opens from a switch or a remote, so you can vent the room without a pole.
Does the room lack a window altogether?
A landing or hallway in the middle of the house, with no outside wall, may suit a sun tunnel. It carries light down a tube from a small dome on the roof, which suits a space where a full rooflight would need too much structural change.
Is there something particular about the building?
A house in a conservation area, or a listed one, may need a conservation rooflight, which sits flush and slim. A deck or a floor that people stand on points to a walk-on rooflight. And where an old unit has failed, a misted rooflight replacement keeps the opening and renews the glass.
From the spot to the type
| Spot | Roof | Type to look at |
|---|---|---|
| Worktop in an extension | Flat | Roof lantern |
| Top stair, in the slope | Pitched | Roof window |
| Basin, no outside wall | Any | Sun tunnel |
| Desk under the rafters | Pitched | Opening roof window |
| Dark dining table | Flat | Flat rooflight |
Rules
What the building rules add
Position, size and type are the design. A few rules sit around them, and we handle them as part of the job.
Cutting a fresh opening that changes the structure of the roof needs approval, which comes from the local authority or a registered building control approver. Swapping an old rooflight or roof window for a new one is also controlled work, with the new unit held to the Part L thermal limit for its kind. Notifiable work comes with a Building Control notification, which is ours to handle, and installation follows the current regulations.
Two further points are worth knowing early. There is no Building Regulations daylight requirement for houses in England, so the amount of light is a choice for you, not a rule. Escape is the other point. If the room is in the roof and the rooflight must serve as an escape window, height matters. Only storeys no higher than 4.5 m from the ground can use a roof window that way, so a loft conversion in a two-storey house calls for a protected stair.
Planning is usually simple for a house, because rooflights often fall under permitted development, but it has conditions and not every property qualifies. Flats, listed buildings and conservation areas differ. Read our planning guide before you settle on a design, and ask Derby City Council if you are in the city.
Next step
From your spot to a written quote
The survey is free, and it happens before any price. We see how the room, your spot and the roof fit together, and measure what we need. After that you receive a written quote with a fixed figure that stays the same on the day. Where several options suit your spot, we lay them next to each other so you can compare what each does for the light.
If you would like to know what moves the final figure first, our page on what affects the cost lays it out without guessing numbers. And the work itself comes with a 10-year workmanship guarantee in writing, described on our guarantee page.
When you are ready, book a free survey and tell us where you stand. A photo of the spot, taken from where you usually look up, is enough to start. You can send it by WhatsApp on 07880 284133 or add it to the form.
