Planning permission is the council's consent for development. Many small changes to a house do not need it, because national rules called permitted development grant the right in advance. For a window in the roof, that right sits in Class C of Part 1 of Schedule 2 to the General Permitted Development Order 2015, usually shortened to Class C.
The rule is short, and people often assume it is stricter than it is. This guide goes through it one limit at a time: how far the window may stand proud of the slope, how high it may reach, what happens on a side slope, and what the class leaves out. It then looks at the designations common around Stroud, since a conservation area or a listing is where plans usually stall. Building Regulations are a separate matter, covered in roof windows and Building Regulations, and the service itself is described on our roof windows and skylights page.
What Class C gives you, and what it does not
Class C covers any other alteration to the roof of a dwellinghouse. A roof window or rooflight is the obvious example. If the work meets the conditions, it is permitted development, and you do not need to apply to Stroud District Council. If it breaks a condition, the right falls away and a planning application is the next step.
Two things sit outside the question. First, Class C answers only the planning question. It says nothing about whether the window meets thermal or structural rules, which belong to the Building Regulations. Second, the right can be taken away in particular places or by particular decisions, which later sections describe.
Permitted development is a right you check yourself, not a consent you are given. The council will not stamp your plan, so keep the dimensions of the window and the roof on file.
If you are unsure whether a particular window passes, raise it with the planning officers at Stroud before work starts. We can supply measurements and photographs of the roof to go with your question.
Where to read the rule
The full wording is on legislation.gov.uk, in Schedule 2, Part 1 of the 2015 Order. The paragraphs we quote below are C.1 and C.2 of that page.
The projection and height limits
Class C.1 lists the things that make an alteration not permitted. Two of them concern shape.
No more than 0.15 metres proud
Paragraph C.1(b) rules out an alteration that would stick out more than 0.15 metres from the original roof slope. Think of the slope as a flat sheet laid over the rafters when the house was built; the window may rise a hand's width above that sheet and no more. Measure out from the surface of the slope. A window whose frame and flashing stand 0.15 metres or less above the covering passes this test. A tall frame, a rooflight on a raised kerb, or a window propped up on a thick timber surround may not. The maker's data sheet states the height of the frame above the covering, and our survey notes the thickness of the covering it sits in.
This is why a flush conservation rooflight is so often chosen for older roofs. Because the limit is measured on the original roof, a covering that has already been raised, for example with thick battens and added insulation, can change the calculation.
No higher than the existing ridge
Paragraph C.1(c) stops any part of the alteration rising above the top of the original roof. For a roof window set into the slope, that is rarely a problem, since the window sits below the ridge. It matters for rooflights at the top of a roof, or for projecting glazing near the ridge line.
Several windows
The class does not set a maximum number of windows, but each must meet every condition. If you plan several along one slope, check the cumulative effect on the roof's appearance before assuming it is fine, and raise any doubt with the planning officers.
Side slopes: when the window must be obscure and fixed
Paragraph C.2 covers a roof window set into a slope that forms a side of the house. A side elevation is one that cannot be identified as the front or the back. On a typical gabled house both slopes face front and back, so the condition seldom bites; it matters for the side hips of a hipped roof, or for a house whose ridge runs from front to back.
A window in such a slope must be obscure-glazed. It must also be non-opening, unless every part that opens sits more than 1.7 metres above the floor of that room.
What 1.7 metres means in practice
A loft room has a sloping ceiling, so a window set low in the slope can have its openable sash well within 1.7 metres of the floor. In that case it must be fixed and obscure. A window set high, with the lowest openable edge above 1.7 metres, may open, but it must still be obscure-glazed: the 1.7 metre height relaxes only the non-opening rule.
Front and rear slopes
The side-elevation condition does not apply to the front or rear slopes. A window there can be clear and openable, provided it meets the projection and height limits. On a terraced hillside street, a rear slope is often the natural place for a loft window for that reason, as well as for the view.
What Class C leaves out: chimneys, flues and solar
The second thing to understand about Class C is its edge. Paragraph C.1(d) takes chimneys, flues and soil and vent pipes out of the class altogether, along with solar photovoltaic and solar thermal equipment. Those fall under other classes, with their own rules.
This matters on a combined job. A loft conversion that adds a roof window, a new flue for a stove and solar panels on the same slope involves three separate questions. The window is Class C. The flue and the panels are not, and each needs its own check against the Order.
Windows and dormers are different
A dormer is a vertical window projecting from the roof, with its own small roof, and it is not a roof window. It falls under Class B, which covers additions to the roof, and that class has the stricter condition described in the next section.
Buildings that are not a single house
Class C speaks of a dwellinghouse. If your building is a flat, a shop with living space above, or a commercial unit, check with the planning officers before assuming the class applies.
Conservation areas, the National Landscape and Article 4
Here is the point that surprises people. Class C has no exclusion for land in a conservation area or the Cotswolds National Landscape. A roof window that meets the conditions is permitted development on that land too. The designation alone does not take the right away.
Compare the dormer. Class B, at B.1(f), is not permitted if the house is on article 2(3) land, which includes conservation areas and the National Landscape (still legally an Area of Outstanding Natural Beauty). So a dormer loft conversion needs a planning application in those places, while a roof window may not.
Where Article 4 can take the right away
An article 4 direction withdraws specified permitted development rights across a defined area, and a condition attached to an earlier planning permission can have the same effect. Stroud District has 41 conservation areas, with Article 4 directions in five of them: Frampton on Severn, Bisley and Wotton Under Edge hold three, and Stroud's own town-centre areas the other two. The council's page does not spell out whether roofs come within them, which simply points readers to the planning department. That is our advice too. Our answer on roof windows in a conservation area applies these rules to one designation.
The Cotswolds National Landscape
Just over half of Stroud District's land lies within the Cotswold AONB, now called the Cotswolds National Landscape. The board that promotes it is not the planning authority, and it does not grant or refuse consent. Any application goes to Stroud District Council, which makes the decision.
Three Stroud roofs, three different answers
The same window can get a different answer on different roofs, so it helps to run the tests on typical situations. These are illustrations of how the rules apply, not a record of particular jobs.
A rear slope on a terrace
A slate terrace on a Stroud hillside, outside any Article 4 area, with a conservation rooflight on the back slope. The unit sits flush, so it clears the 0.15 metre limit, it is nowhere near the ridge, and it faces the garden, not a neighbour. Class C is satisfied and there is no planning application to make. Building Regulations still apply, and we explain them at the survey.
A hipped semi with a side slope
A hipped roof has a slope on each side of the house. A window in the side hip falls under the side-elevation paragraph, so it must be obscure-glazed in every case, and fixed shut unless the opening part is above 1.7 metres. The rear slope has no such condition, which may settle where the window should go.
A stone slate cottage in a conservation area with an Article 4 direction
Here the starting point is a phone call to the planning team. Class C may well allow a window, but the direction could have withdrawn the right for this house, and the council's published page is silent on roofs. If the cottage is also listed, consent is needed anyway. With stone slate, the opening and the courses around it are set out by hand, so the survey also records the existing courses before any design is settled.
Listed houses, replacements and Building Regulations
A listed building is outside the ordinary run of permitted development in practice. The 1990 listed buildings legislation, in section 7, bars anyone from altering a listed house in a way that damages its special character unless authorised first, and section 9 makes ignoring that an offence. The council also points out that no grade of listing is exempt, and the protection covers the whole building, indoors and out. A new roof window in a listed roof will almost always need listed building consent, whatever Class C says, and only the council can tell you otherwise. Speak to the council's conservation officers before ordering anything.
Swapping an old window for a new one
Replacing an existing roof window is not the same as adding one. If the new unit sits where the old one did, the planning question is still the council's to answer, not the contractor's. Our guide to replacing a roof window covers the practical steps. Building Regulations apply to replacements as well, since a replacement element in an existing dwelling should meet the limits in Part L Table 4.2.
A short checklist before you order
- Find out whether the house is listed.
- Ask whether an Article 4 direction or a planning condition applies.
- Check the frame height against the 0.15 metre limit.
- Check any side-slope window against the obscure-glass rule.
- Keep photographs and measurements.
At the survey we photograph your roof and give you the measurements these checks need. We cannot give legal advice, so the planning team has the last word.