Rooflights, planning and Building Regulations in Devon

Most houses have permitted development rights, which means certain alterations can be made without a planning application. Roof alterations fall under Class C of Part 1 of Schedule 2 to the General Permitted Development Order (GPDO), and rooflights are covered by it. The conditions are short:

• the window must not project more than 150mm beyond the plane of the existing roof slope;
• it must not be higher than the highest part of the roof;
• a window in a side-facing roof slope must be obscure-glazed, and non-opening unless the openable part is more than 1.7m above the floor of the room.

Most roof windows fitted into a slope are comfortably within the first limit, because they sit close to the covering. Flat rooflights on kerbs, and lanterns, are the units that need a check, since a kerb adds height. A low, slim unit on a flat roof can pass, while a tall lantern over an extension generally needs a planning conversation. Lanterns on new extensions are usually dealt with as part of the planning permission or the permitted development for the extension itself, so look at the original drawings.

It is worth knowing that these rights belong to houses. They do not apply to flats or maisonettes, whose owners do not have householder permitted development, nor to buildings whose rights have been removed by a planning condition, which is common on newer estates. If your home was built in the last few decades, read the original planning decision for any condition limiting alterations.

A conservation area does not by default stop you fitting a rooflight. Class C permitted development still applies in a conservation area, provided the other conditions are met. What a conservation area does add is the chance of an Article 4 direction, which is a local order removing specific permitted development rights, often for alterations to a roof slope facing the street.

Exeter has conservation areas, including those that cover parts of the city centre and some of the older residential streets, and Topsham, Sidmouth, Budleigh Salterton, Totnes and many Devon villages have their own. Whether any given street has an Article 4 direction is a question for the council. It cannot be guessed from the age of the houses, because directions differ from one conservation area to the next.

Listed buildings are different again. Listed building consent is needed for any alteration that affects the character of the building, and cutting a hole in a roof and ceiling does. That applies to the interior as well as the exterior, so it covers the new ceiling opening, and it applies whether or not the home is also in a conservation area. Listed building consent is a separate application from planning permission and has its own conditions. Historic England's website explains how listing works, and the local authority's conservation officer is the person to speak to. A conservation rooflight in a slim steel frame is the product most often accepted on a historic roof, but acceptance is not automatic.

National parks are what the GPDO calls Article 2(3) land. Permitted development is available there, but some rights are restricted, and the park authority, not the district council, is the local planning authority. Dartmoor National Park Authority covers planning inside the Dartmoor boundary, including villages such as Moretonhampstead and Chagford. Exmoor National Park Authority does the same for Exmoor, which includes Dulverton on the Somerset edge of our area.

Several towns sit close to the Dartmoor boundary, and Bovey Tracey, Ashburton and Buckfastleigh need care, because the park boundary runs close to or around them. Check the boundary on the park authority's map rather than assuming, and ask the authority if the answer is unclear. A rooflight in a roof slope that faces away from public view can be treated differently from one facing a lane, and the authorities care a great deal about the character of granite and slate roofs.

Devon has no single planning authority, which catches people out. The one that applies depends on where the house is.

• Exeter City Council covers Exeter and Topsham.
• East Devon District Council covers the east side, including Exmouth, Budleigh Salterton, Sidmouth, Honiton, Ottery St Mary, Seaton, Cranbrook and Broadclyst.
• Mid Devon District Council covers Tiverton, Cullompton, Crediton and the Culm valley villages.
• Teignbridge District Council covers Newton Abbot, Teignmouth, Dawlish, Chudleigh and the Teign and Exe estuary villages.
• Torbay Council covers Torquay, Paignton and Brixham.
• South Hams District Council covers Totnes and Stoke Gabriel, and West Devon Borough Council covers Okehampton and North Tawton.

Planning enquiries, Article 4 checks and listed building questions all go to the relevant one. Many councils run a pre-application service for a fee, and it is worth using if your property is listed, in a conservation area or just unusual. If you are not sure which council covers a house near a boundary, say in a village between two districts, the council tax bill or the council's online map will say.

The Planning Portal at planningportal.co.uk has an interactive guide to rooflights and a way to apply, and gov.uk publishes the permitted development rules in full.

Building Regulations apply whatever the planning position is. They are national rules, in England set out in the Building Regulations 2010 and the approved documents that explain them. A rooflight triggers them in two ways, and the difference matters.

A new rooflight in an existing roof

This is building work. Cutting or trimming rafters is a structural alteration, so the new opening has to be framed to carry the roof loads, and the new window has to meet the energy rules of Part L. It needs Building Control approval before or as the work is done.

Replacing a whole rooflight or roof window

This is notifiable too. A window is a controlled fitting, so a replacement frame and glass has to meet Part L and be notified to Building Control.

The exception is replacing only the sealed glass unit in an existing frame. That is not notifiable, because the frame stays in place. Whether it is a good idea is another matter, which is why a survey comes first, and our page on misted and failed rooflights covers when a glass-only swap makes sense.

With Brightview, you do not need to manage any of this. We handle the Building Control notification where the work is notifiable, and the finished installation meets current Building Regulations. Our short answer on whether skylights need Building Regulations approval covers the same ground in fewer words.

Part L of the Building Regulations is the conservation of fuel and power. For rooflights, replacement and new units must meet the limiting U-values set out in Approved Document L, Volume 1, in its 2021 edition. A U-value measures how quickly heat passes through a material, so a lower number means a better-insulating window. The figures are different for roof windows and for rooflights in other forms, and they change when the guidance is revised, so the figures to work to are those in the current approved document, not anything quoted from memory.

That has practical effects. Double glazing with a low-emissivity coating and a warm-edge spacer is now the baseline, and triple glazing is sometimes chosen to give margin. A rooflight that was fine a few decades ago is unlikely to meet the standard now, which is one reason replacement is regulated. Our page on energy efficient rooflights goes through the options.

Part L also covers how well the window is fitted: the insulation wrapped around the frame, the airtightness at the junction and the lining that continues the insulation into the room. A good window badly installed will not perform, which is why the finish inside the opening matters for compliance as well as appearance.

Three other parts of the regulations can touch a rooflight, each in a limited way.

Part B, fire safety

In a loft conversion, a roof window can serve as an escape window if it meets the size and position requirements in Approved Document B. Rooflights near a boundary may have limits on the type of glazing and plastics used, so a lantern close to a neighbour's wall needs checking. The wording of the document is technical, and your Building Control officer will confirm what applies.

Part F, ventilation

Rooms need background and purge ventilation. An opening rooflight can contribute to purge ventilation, which is useful in a kitchen or bathroom extension where there are few other openings. Electric opening units make that practical when the window is out of reach.

Part K, protection from falling, collision and impact

Part K4 deals with glazing in critical locations: doors, the panels beside them and low-level glazing. It does not require laminated glass in a rooflight. A laminated inner pane is nevertheless good practice for overhead glazing, and widely recommended by the industry. Walk-on glass is a separate matter, specified to structural guidance for loading rather than to the ordinary rules, so it needs an engineer's input.

Some roofs and buildings need an extra step, and the common ones in Devon are these.

Thatched roofs

A rooflight can go in a thatched roof, but it needs a purpose-made kerb with the thatch dressed around it, planned with a thatcher. There are fire and weathering considerations, and a thatched house is often listed too. Our answer on rooflights in thatched roofs covers it.

Flats and maisonettes

Without householder rights, a rooflight usually needs planning permission, and the freeholder or management company's consent as well, since the roof is normally shared. Do not skip the lease.

Cob and stone cottages

Planning is rarely the issue unless the building is listed. The issue is structural: irregular rafters and thick walls mean the Building Control officer may want details of how the trimmed opening is supported.

Party walls

Where the work is close to a shared wall, the Party Wall etc. Act 1996 can apply. It rarely does for a rooflight in the middle of a roof slope, but a semi-detached or terraced house with the opening near the boundary should check.

A sensible order saves time. Start by finding out which authority covers the house and whether it is in a conservation area, a national park or a listed building. Then decide the type and size of unit, because the planning rules depend on the projection and the Building Regulations on the structure. Next, ask for a survey, and have the quote name how the Building Control notification will be handled and by whom.

If the property needs planning permission or listed building consent, apply before you commit to the job. Permission for the roof glazing does not cover the ceiling opening in a listed home, and the other way round, so ask about both.

When work finishes, you should receive the paperwork for the notification or approval, and you should keep it. A buyer's solicitor will ask for it years later, and it is easier to file it now than to find it then. You will also have a written finish schedule from us, recording the ceiling, the lining and how it was finished, which belongs in the same folder.

More on the types and the finish is on the skylight and rooflight installation homepage, and the difference between the products is set out in skylight or rooflight: what is the difference. When you are ready to start, ask for a quote and we will arrange a survey and talk through the planning position for your own address.