Will a new VELUX match the ones already on my roof?

Three things decide whether a new window reads as part of the same row rather than an odd one out: the size, the exterior colour and the position on the slope. Get those three right and a window bought this year will sit comfortably alongside one bought a decade ago, even though no two VELUX frames from different periods are tooled identically.

People often assume "matching" means finding the exact same product, discontinued model and all. It rarely does. VELUX keeps size codes constant across generations precisely so that a house with three roof windows fitted at different times can still be extended or replaced window by window without the whole row being redone at once.

The size code, a letter and two digits stamped on the frame or printed on the data plate inside it, fixes the width and height of the opening. Order a new window in the same code as the ones either side of it and the outer dimensions match exactly, whatever year each one was bought in. Rows of roof windows are usually planned to a size that suits the rafter spacing in that particular roof, so the existing spacing is often the strongest clue to what the new one should be too.

If the code has weathered off the outside of an existing frame, it is worth checking the data plate before assuming a size from measurements alone. Our guide on where the size code sits on an existing window shows where to look. Our page on choosing the right VELUX size covers how the code maps to a room and a view where there is no existing window to match at all.

VELUX's standard exterior finish across most of the current range is a grey polyurethane coated aluminium, which is why two windows bought years apart usually turn up in the same colour without anyone asking for anything special. Where the difference shows up is between ranges: a conservation window, a flat roof window and the mainstream pitched range have not always shared exactly the same standard finish, so if the existing window came from a different part of the catalogue, the new one needs choosing with that in mind rather than assumed to match by default.

Our guide to VELUX glazing options and the conservation-specific page on the VELUX conservation range set out where the ranges part company, which is the more useful question to settle before ordering than the colour name alone.

Frame depth is the part nobody thinks to ask about. VELUX has increased the depth of its frame over successive generations to carry more insulation, so a current window ordered to an old size code fills the same opening but is not tooled to the same millimetre profile as a frame bought fifteen or twenty years ago. Seen from the ground, this rarely reads as a mismatch. Seen close up, standing under both windows in the same loft, the sash edge and the shadow gap around it can sit a shade differently on the new one than on its older neighbour.

From inside the room this matters more than it does from outside, because it is the frame edge and the reveal that decide how much sky each window actually shows. A new window installed a metre or two from an old one will usually give a very similar view, but "very similar" is not "identical", and it is worth seeing that difference on paper before the roof is opened rather than discovering it afterwards. Our page on how much of the frame you will see from inside a VELUX explains what changes the reveal.

The opening type is worth checking too. An older window may be a plain centre pivot, while a current equivalent in the same size code might be offered as either centre pivot or top hung. Matching how the window opens, not only its size and colour, keeps the row consistent to use as well as to look at. Our guide comparing GGL and GPL, centre pivot or top hung sets out the difference.

A short table covers the points a survey settles before a new window goes in next to an existing one.

The roof covering gets the same attention as the window itself, because the flashing is chosen to suit the tile, slate or sheet material on that slope rather than to suit the window alone. Our guide on which flashing suits your roof covering covers how that choice is made, and it is checked at the same visit as the size and colour.

Occasionally the existing window is old enough, or from a range discontinued long since, that no current product will match it feature for feature. In that case the more useful goal is a window that sits comfortably in the row rather than one that is provably identical: the same size code where the rafters allow it, the closest current colour to the existing finish, and a position and cill line that keeps the row visually level. That is a judgement made on site with both windows in view, not one worked out from a brochure beforehand.

It also helps to decide what the new window needs to do before chasing an exact match. A window added mainly to bring more sky into a landing or a bedroom does not need to be indistinguishable from its neighbour to do that job well; it needs to be placed and sized for the view from where someone actually stands or lies in that room. Every quote comes with a sightline sketch, so the view the new window will give is settled on paper before a decision is made on how closely it needs to match what is already there. Our VELUX window installation page covers the wider job, and our cost guide sets out what affects the price of adding a window to an existing roof.

Do all VELUX windows leave the factory in the same exterior colour?

Not across the whole catalogue. The mainstream pitched range shares a standard finish, but the conservation and flat roof lines have their own standard colours, so a window from a different part of the range is not guaranteed to match one from the mainstream line without checking first.

Will an old size code still be available today?

Size codes are kept in production for a long time precisely so an existing opening can be matched years later, but a very old code from a discontinued generation is worth confirming before assuming it, which is what reading the data plate on site is for.

Does the frame depth difference show from inside the room?

It can, in the shadow gap and the angle of the reveal close to the frame, more than in the size of the opening itself. It rarely changes how much sky the window gives, which is the point a sightline sketch settles before the work starts.

What if the two windows end up slightly different once both are fitted?

A small difference in tone or frame depth between an older window and a new one is normal rather than a fault, and it is something we flag at survey stage if it is likely, so there are no surprises once the new window is in.