What decides the access
The access for a roof window is set by three things: how high the slope is above the ground, where the window sits on that slope, and how much outside work the job involves.
Fitting a roof window has an inside half and an outside half. The inside half is cutting the opening, trimming any rafters, fixing the frame and lining the reveal. The outside half is stripping back the tiles or slates, fitting the underfelt collar and flashing kit, and re-laying the roof covering tightly around the frame. On many pitched roofs a fitter can lean through the new opening and reach most of that outside work. The parts they cannot reach safely from the opening are what decide whether anything more is needed.
The Work at Height Regulations 2005 require the work to be planned so that a fall is prevented where possible, and the safest reasonable method is used. That is why the answer is a judgement made at the survey rather than a fixed rule. The roof window installation page explains how that survey fits into the wider job.
Access options, from lightest to heaviest
There is a sliding scale of access, and the right point on it depends on the roof in front of you, not on the size of the window alone.
| Access | Typical use | Footprint |
|---|---|---|
| From inside only | Low slope, window mid-roof, simple flashing | None outside |
| Roof ladder | Tiling above or beside the frame | Ladder on the slope |
| Mobile tower | Single-storey and low two-storey roofs | Garden or drive |
| Scaffold with edge protection | High, steep or exposed slopes | Along the elevation |
Working entirely from inside suits a window set in the middle of a loft slope, where the flashing and the courses of tiles around it are within arm's reach of the opening. A roof ladder hooked over the ridge gives a safe foothold for reaching the tiles above the frame. An aluminium tower, assembled by trained people, suits a lower roof such as a single-storey rear extension or the back of a bungalow. Full scaffolding with guard rails at the eaves is the heaviest option and the one that gives the most protection over the longest stretch of roof.
The companion answer, can a roof window be fitted from inside, looks at the inside method in more detail.
When scaffolding is the sensible choice
Scaffolding earns its place when the drop is high, the slope is steep, or the outside work runs across a wide area of roof.
- Three-storey houses and town houses, where the eaves are high above the garden.
- A window set low on the slope, close to the gutter, where anyone working outside would be leaning over the edge.
- Steep pitches, where a roof ladder gives a poor foothold.
- Roof window combinations of two or more windows side by side or stacked, where the flashing and re-tiling cover a wide strip of roof.
- Loft conversions where several windows, a dormer and re-roofing happen at once, and the scaffold serves the whole job.
- Slate roofs, where more of the covering may need to come off and go back around the frame. The slate roof answer covers why.
On a loft conversion the main builder usually has scaffolding up already, and the roof windows go in while it is there. That is the easiest arrangement of all: the loft conversion guide explains how the windows sit alongside a dormer.
Cambridge roofs and what they tend to need
The housing around Cambridge covers the whole range, so the access for one street can be quite different from the next.
A Victorian or Edwardian terrace in Romsey, Petersfield or off Mill Road has a rear slope over a narrow garden and often a single-storey kitchen extension below it. A window placed mid-slope can often be fitted from inside, and where a tower is needed it may stand on the extension roof or in the garden, depending on what that roof can take. The front slope faces the street, which brings a different question, covered below.
A 1930s semi in Cherry Hinton or Chesterton usually has a hipped roof at two storeys, with the slopes reachable from a tower on the drive or in the garden. Newer three-storey town houses at Eddington, Trumpington Meadows or Great Kneighton have high eaves, so outside work on those roofs normally calls for a scaffold. Village cottages vary widely: some have low eaves you can almost touch from the garden, others have steep, tall roofs over a lane. The hipped roof answer looks at placing windows on those smaller slopes.
Scaffolding over a pavement or a neighbour's garden
When a scaffold has to stand on the public pavement, it needs a licence from the highway authority before it goes up.
Across most of the area that is Cambridgeshire County Council, and the scaffold contractor normally applies for the licence and arranges the lighting and protection it asks for. A front slope on a Cambridge terrace, where the front wall sits on the pavement line, is the usual case. If the only good place for a tower or scaffold is in a neighbour's garden or a shared passage, that needs their agreement first. None of this is unusual, but it takes time, so it belongs in the plan from the start rather than the week before the fitting.
How access fits the light plan and the quote
Access is agreed at the light survey, written into the quote, and never left as a surprise for the day.
At the survey we look at the slope from outside as well as in: the height of the eaves, the pitch, the covering, what stands below and where a ladder, tower or scaffold could go. The written light plan then sets out the position, size, glass and shading, and the quote states the access method alongside them. Access is one of the factors that moves the overall cost, and the costs page explains how it sits with the others. Where the work is notifiable we handle the Building Control notification too, as the building regulations answer sets out.
If you are weighing up a roof window and want to know what your own roof will need, book a light survey or message us on WhatsApp.
Questions people also ask
Do you need scaffolding to fit a pitched roof skylight on a bungalow?
Rarely. Bungalow eaves are low, so most of the outside work can be reached from inside, from a roof ladder, or from a small tower. Scaffolding comes in only when the roof is unusually steep or the window sits right at the edge.
Does the scaffolding go up for the whole installation?
Only for as long as the outside work needs it. A single roof window is usually fitted in one to two days including the lining, so any tower or scaffold is on site for a short spell, often going up the day before and coming down once the flashing and tiling are finished.
Is a replacement roof window easier to access than a new one?
Often, yes. When a new window goes into the same opening, much of the work is done from inside and the flashing kit is made to suit the existing frame depth, so there is less outside work. The roof height still decides whether a ladder, tower or scaffold is needed for the part that remains.
Can the window be cleaned without scaffolding once it is in?
Yes. Centre pivot and most top hung roof windows turn so the outside pane can be cleaned from inside the room. The cleaning answer explains how.
