The short answer
With a roof window, the model matters more than the glass size. Measuring the glass or the opening alone will not tell you whether a blind fits, because frames, sash shapes and fixing points differ between makes and between generations of the same make. So the job is really two things: identify the window, and record a few sensible measurements as a back-up.
Start with the label
Most roof windows, including Velux, carry an identification plate on the frame or the edge of the sash. It usually shows a manufacturer name and a model or type code. Photograph it, then write the code down. Our guide to identifying your roof window walks through where to look. If the plate is painted over or missing, photographs of the whole window and its frame can still help us work out what you have.
For windows from Velux, there are dedicated blinds made to match specific window types, and our page on Velux roof window blinds explains how that works in practice. Other makes may need a different approach, so a blind for one will not necessarily suit another.
What to record
Even with a label, it helps to have a few details to hand. Write these down and take photos as you go:
- The model or type code from the label, plus the manufacturer.
- The overall look of the window from inside, with the sash closed.
- The sash opening style: whether it swings, tilts or pivots, and where the handle sits.
- The width and height of the visible glass, measured in millimetres, and where you measured from.
- The frame width around the glass, because some blinds sit on the frame.
- The pitch of the roof if you know it, since it can affect how a blind hangs and stays in place.
- Any obstructions, such as a control bar, trickle vent, deep lining, or a window sill below.
Measure more than once and write the numbers down straight away. A phone photo with a tape measure held against the glass is a quick way to double-check later.
Measure safely
Roof windows are often high up and awkward to reach. Use a stable step or ladder, ask someone to steady it, and keep both feet inside the room rather than leaning out or climbing on to the roof. If the window is out of reach, photograph what you can safely see and leave the rest for the visit.
Why the usual rules work differently
With a normal window, you can decide whether a blind goes inside the recess or over the frame and then measure accordingly. Roof windows are different in a few ways:
- The blind often attaches to the frame or the sash itself rather than the wall.
- It may need guide rails or side channels so that the fabric stays close to the glass as the window slopes.
- The sash may need to open fully with the blind in place, and in some cases a blind has to be operated with the sash closed.
- Cords, poles or control bars have to be reachable without a risk of tangling or strain.
These details are why a measurement on its own is not enough. They are also why it is worth looking at the product information for any blind you are considering, so you know how it attaches and whether it suits your window.
Choosing the type of blind
Once the model is known, the choice is a mix of light control, heat and practicality. Roof windows catch strong sun, and a room can feel warm in summer and bright in the morning. A light-filtering fabric softens the glare but keeps the room light. A blackout fabric darkens the room for sleep. Some blinds also offer an insulating effect that helps with heat, though results depend on the product and the room, so ask us what a particular fabric is designed to do.
You can read more about the options on our roof blinds page. If your loft conversion is a bedroom, our blackout blinds page is a useful next stop.
What if I cannot find the label?
Do not worry. Many people cannot, particularly if the window was fitted by a previous owner. Take clear photos of the inside of the frame, the handle, the sash edges and the whole window from a distance. Measure the glass and the frame as described above. We can often identify the type from that, or confirm it when we visit. If a window has a very old or unusual design, we'll say so honestly rather than guess.
Checklist before you call
- Photograph the label, or note that you could not find one.
- Photograph the whole window, closed and open.
- Note the width, height and frame size.
- Write down what you want the blind to do: darken, cool, add privacy, or look good.
- Note if anyone in the home is a young child, because cords matter. See our child safety page.
Let us measure for you
If you would rather not balance on a ladder, we can look at the window with you. Book a free measure and we'll identify the model, check the details and talk through the choices.
