How close to a neighbour can a roof window be?

Most roof windows on a house come under permitted development, the relevant provision being the General Permitted Development Order, Schedule 2, Part 1, Class C. The conditions concern the window itself:

• it may stand no more than 150mm clear of the existing roof slope;
• it may not rise above the highest point of the roof;
• a window in a side-facing roof slope, which is the slope facing a neighbour, has to be obscure-glazed, and fixed shut unless the openable parts sit over 1.7m above the room floor.

The side-slope rule is the one that links to neighbours. On a gable-ended or hipped house, a roof window in the slope that faces next door needs obscure glass, and it must be fixed shut or open only well above floor level. A roof window on the front or rear slope has no such condition, however close the neighbouring house is.

These rules are for houses. Neighbouring flats and maisonettes are not covered by householder permitted development, listed homes require listed building consent, and a conservation area may be under an Article 4 direction. In any of those cases, speak to the council planning team before you order.

The distance question that is written down is in the fire rules of Building Regulations. Approved Document B limits how much unprotected area, glazing and similar openings, may sit close to a boundary, because fire can spread across a gap. These rules are mostly worked out for walls. Rooflights are covered under the roof coverings section, where the concern is the spread of fire across the roof from or to a neighbouring building.

In practice, the roof covering and any plastic rooflight material have to meet a fire performance classification that depends on how close the roof is to the boundary. Roof windows with glass are normally straightforward. Plastic rooflights and some polycarbonate domes face tighter limits near a boundary. Terraced and semi-detached houses, where the roof is shared or only a wall apart, deserve extra care on a party wall line. We check the position of the boundary at the survey, and the wording of the Building Control notification follows from what we find. Use cautious wording when you read about this elsewhere, because the detail depends on the product's classification and on the exact distance.

If the new opening affects the roof structure that is shared with your neighbour, or if the rafters and trimmers bear on or near a party wall, the Party Wall etc. Act 1996 may apply. A roof window set in one side of a semi-detached roof, between rafters on your own side, is rarely an issue. Cutting into a party wall, or into a chimney breast or beam that is shared, is different. If there is any doubt, take advice before work starts. The notice has to be served before the work begins and it is the homeowner's responsibility.

A roof window looks upwards at an angle, so you can usually see a lot less of next door than you could from a vertical window. What you see tends to be the sky, not into a bedroom. That changes where it sits: a window set high on the roof near the ridge looks mostly at sky, and a window low in the slope sees more of what is nearby.

Neighbours may see in from a taller building, or from a window higher up across a narrow gap. A terraced street in Exeter, with houses close together and loft rooms opposite each other, is where this comes up. Options include obscure glazing in a bathroom or bedroom, a blind, or moving the window further up the slope. If the room is a bathroom, there is a related page on fitting a roof window in a bathroom.

Neighbours with matching houses sometimes both want a loft window, and a pair of windows in mirrored slopes on a semi-detached roof is common in 1930s streets such as those in Heavitree. Each owner can fit one in their own slope under the same permitted development rules, and each window is judged on its own projection and height. If a window sits close to the party wall line, the roof structure there is shared, so rafters and trimmers should be kept on your own side of the wall and the position confirmed at the survey. A little space between the frame and the wall also leaves room for the flashing and for a neat lining inside.

It is also worth thinking about the next owner. A window that looks directly across a narrow gap at a neighbour's bedroom may become a source of friction, whereas one set a little higher or further along the slope costs nothing extra to arrange at the planning stage.

Closeness to a neighbour has a practical side that has nothing to do with the regulations. Working on a roof near a boundary may mean scaffolding that reaches into their garden, or sheeting over a shared gutter. Where access has to cross the neighbour's land, the permission is theirs to give, and it is best asked for in advance. A short conversation before the work starts, with a rough date, avoids most difficulties. Dust and noise are also worth a mention, even for a job of a few days.

The generally true position is above, but the answer for a particular house depends on the roof shape, the boundary, any shared structure and the designation of the area. Dartmoor and Exmoor are national parks, where some rights are restricted. Conservation areas and listed buildings in Exeter, Topsham and across Devon may carry their own rules. The local planning authority can confirm what applies. You can find general guidance on the Planning Portal.

At a survey, we look at the slopes of your roof, the boundary and the neighbouring roofs, and say in writing where the window should go. We handle the Building Control notification. Our overview of roof window installation in Exeter covers the full job, and if the roof is a loft conversion, see whether a roof window can be a fire escape. When you are ready, ask for a quote.