The short answer
Not always. A single roof window on a low pitched roof can often be replaced from a roof ladder or an access tower. A lantern, a large flat rooflight, an opening high above the ground or any roof without safe edge protection calls for scaffold. The height, the roof surface and the weight of the new unit decide it, and we settle it at the survey.
Three things that decide the access
Nobody picks scaffold for its own sake. It goes up because one of three facts about the roof demands it.
The first is height. The Work at Height Regulations 2005 require work at height to be planned, and to be done with the right equipment for the task. Falling from a roof edge is a serious risk, so a crew working near an unprotected edge needs edge protection, and scaffold is the usual way to provide it. A bungalow with the opening a short reach from the eaves is a different case from a three-storey house with the opening near the ridge.
The second is the roof itself. Clay tiles, concrete tiles and natural slate are all walked on differently. Old tiles can be brittle, and a roof that has sat for decades may not take a person's weight between the battens without a crawling board or a roof ladder to spread it. Flat roofs have their own problem, which is the perimeter. A flat roof is easy to step on and easy to step off, so the edge needs guarding.
The third is the unit. A roof window is light enough for two people to lift into place from a ladder or from a platform. A large flat rooflight or a roof lantern is heavy, awkward and fragile, and it often has to be lifted from ground level up to the roof. Glass of that size cannot be carried up a ladder. It needs a platform to land on and a way to get it there, and a hoist or crane is sometimes part of the answer.
The options, from lightest to heaviest
Access equipment comes in steps. The lightest that does the job safely is the right one, and no heavier.
| Access | Suits | Limits |
|---|---|---|
| Roof ladder and harness | Small roof window, low pitch | Not for heavy glass |
| Access tower | Low eaves, small to medium unit | Needs firm, level ground |
| Full scaffold | Lanterns, high roofs, large units | Takes a day to erect |
| Hoist or crane lift | Very large glass units | Needs space to set up |
A tower is a freestanding frame on wheels or feet, and it needs a flat, firm base. It works well on a patio and badly on soft lawn or a sloping drive. It also has to stand close enough to the eaves to be useful, which is a problem where there is a conservatory, a garage or a flower bed in the way.
Full scaffold is fixed to the building and gives a working platform with guard rails all round. It is the best choice for anything heavy, because the crew can stand squarely to lift and fix the unit instead of reaching from a ladder. It costs more and takes time to put up and take down, which is why we do not use it where a tower would do. Our costs page explains what drives the price of a job, including access.
Where a flat roof changes the picture
A flat roof is often reached from inside the house or from a lower roof, and that can make scaffold unnecessary. It does not remove the edge problem.
Where the flat roof is a single storey extension, the work can often be done from a tower or from a scaffold that covers only that one side. A full scaffold around the whole house is not needed for a kitchen extension at the back. What the regulations want is edge protection at the place where someone could fall, and a short run of scaffold or a set of edge guard rails can provide it.
The unit is the other question. A large flat rooflight over a kitchen island can be a single sheet of glass of a size that takes several people to handle. A lantern arrives in sections or as a built frame, and the lift depends on how it is delivered. That is where a flat roof can need a hoist even though the roof is low, because the glass cannot safely be passed up by hand. The detail for these is set out under flat roof rooflight installation and roof lantern installation.
What scaffold means for your garden and your neighbours
The practical worries are the ones people raise second: the lawn, the drive and the road outside.
A scaffold needs ground to stand on. Boards are laid under the feet to spread the load, and they leave marks on soft turf, so the lawn is usually covered or the boards set on protective sheet. A bed of shrubs near the wall may need to be cut back or tied aside. The scaffolders will walk the ground with you before they start.
If the scaffold has to stand on the pavement or extend over the highway, a licence from the highway authority is usually needed, and the scaffolders normally arrange it. In West Sussex that is the county council. In a Crawley terrace or a 1950s semi with a front drive, the front of the house is often the only access, so the question matters.
A scaffold also affects security. A ladder to a first-floor roof is an invitation. A properly run scaffold is boarded off at the bottom or has its ladders taken away at the end of each day.
Questions about access for a replacement
Will I be told before the job whether scaffold is needed?
Yes. We look at the roof, the opening and the ground at the survey, and the access is named on the quote alongside the glazing build. The list of what a quote should include shows where it belongs.
Does the scaffold stay up for the whole job?
It stays up for as long as the work needs it. A single-opening replacement usually needs it only for the days the roof is being worked on. Bigger projects and a run of openings take longer, which is where the time it takes to replace a skylight comes in.
Can a roof window be replaced without any scaffold at all?
Often, yes, when it is small, the roof is sound and the pitch is gentle. A roof ladder and a safe anchor point are used, and the exact method is agreed at the survey. See roof window installation for the common cases.
Is the access cost included in the quote?
It is shown as part of the quote, not added afterwards. If you want the full picture of the job, get a quote and the access, the glass and the quiet spec arrive together.
The job is part of our wider skylight and rooflight installation service around Crawley.