Can a VELUX Be Fitted on a Very Steep Roof?

Every VELUX roof window, sometimes called a skylight, is sold against a pitch range in degrees, and that range is what an installer checks first, not a general impression of how steep a roof looks from the street. A roof that reads as steep from below might be forty five degrees; a dormer cheek can run past seventy. Each of those is a different number on the same measuring scale, and the model, the flashing and even the handle height are chosen against that number.

Peterborough has a wide spread of roof pitches to plan around. Fletton brick terraces close to the city centre often carry a plainer, steeper pitch than the newer township roofs in Bretton, Orton and Werrington, and the stone cottages around Stamford add their own older roof geometry again. None of that changes the underlying rule: measure the pitch, then choose the window.

VELUX's two main pitched-roof opening types cover different parts of the pitch range, and a steep roof usually points to one of them rather than the other.

A centre-pivot sash rotates around a fixed point roughly halfway up the frame, so the top and bottom each travel half the distance a hinged edge would. That is why it stays usable right up near vertical: neither edge has to swing through the full height of the window. See VELUX GGL or GPL: Centre-Pivot or Top-Hung for how the two compare on handle position and cleaning as well as pitch.

Fitting a VELUX on a steep pitch is not a different job so much as the same job with several settings moved. The handle height, the flashing profile and the headroom the sash needs to swing into are all worked out from the pitch reading, and a steep number pushes each of them in the same direction.

• The handle sits higher up the sash on a steep window than on a shallow loft rooflight, because the reach and the closing force are both calculated from the actual angle, not a fixed position.
• Where the roof meets a low ceiling near the eaves, the sash needs clear space to rotate inward without catching on rafters or plasterboard, so that clearance gets checked at survey rather than assumed.
• Rain runs off a steep pitch fast, so there is less standing water at the frame, but a steeper roof takes more wind-driven rain side-on, which is a flashing question rather than a glazing one.
• A window fitted close to vertical behaves more like a wall window for daylight and view, and less like a flat rooflight looking straight up at the sky.

The flashing kit, not the window itself, is what is matched most closely to the roof covering and the pitch together. Plain tiles, interlocking tiles, slate and thatch each need a different flashing profile, and a steep pitch changes how far up the roof that flashing has to run to stay weathertight. Which VELUX Flashing Suits Your Roof Covering sets out the options by covering type; on a steep roof, the installer also checks that the chosen kit is rated for the pitch measured on site, since not every flashing profile is made for the full range a centre-pivot window can sit in.

Not every VELUX style suits every pitch equally. The VELUX CABRIO folds a pair of windows out into a balcony, which needs a pitch shallow enough for the lower sash to open flat, so it tends to sit on a gentler slope than the steepest roofs this question is usually asked about. A standard centre-pivot window with the right glazing and blinds is the more usual answer on a genuinely steep pitch, since both are chosen from the same range regardless of the angle behind them.

A window on a steep pitch is closer to vertical, so what you see from inside shifts too. Looking up through a shallow rooflight gives an almost overhead patch of sky; a steep window reads more like looking straight across at the horizon, with the frame and any glazing bar sitting directly in the eyeline rather than off to one side. That is exactly the kind of detail a sightline sketch is drawn to show before the roof is opened, working from the bed, chair or desk the window actually serves. How Much of the Frame Will I See From Inside a VELUX goes further into how sash depth and lining angle change that view.

None of this changes the basics covered on the VELUX Window Installation page: the window still goes in to current Building Regulations, and where the work is notifiable, the Building Control notification is handled as part of the job. What changes on a steep roof is the detail, not the standard the job is held to. General cost factors, including access and flashing complexity, are covered on the costs page.

What counts as a steep roof pitch for a VELUX window?

There is no fixed cut-off; the number that matters is the pitch measured in degrees on site. Many installers start treating a roof as steep once it passes around fifty to sixty degrees, because that is roughly where a top-hung window stops being the natural choice and a centre-pivot becomes the more sensible one.

Can a top-hung VELUX be fitted on a steep roof?

Below around fifty five to sixty degrees, yes. Past that, the hinge sits at the top of the frame and opens the sash upward and outward, which becomes less practical to reach and operate as the roof gets closer to vertical, so a centre-pivot window is usually specified instead.

Does a steep roof change how a VELUX is measured for a replacement?

The pitch itself is checked again alongside the existing size code, since an older window's flashing was chosen for that same pitch and covering. See where the size code sits on an existing VELUX window for how that reading is taken.

Will a steep roof need scaffolding to fit a VELUX?

Often, yes, simply because a steep pitch is harder and less safe to stand on than a shallow one, so external access is arranged accordingly. That is an access decision made at survey, separate from whether the window itself suits the pitch.