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Glass garden rooms

Bright, open and very easy to get wrong. The rules for attached glass rooms and glazed garden rooms, and how to stop them baking in summer.

Updated 22 October 2026

Two kinds of glass room

• An attached glass room or veranda: usually a glass or polycarbonate roof on aluminium posts against the house, with glass side panels and sliding doors added to enclose it.⁵ Which? says these rooms often work as seasonal spaces rather than fully insulated rooms.⁶
• A detached, heavily glazed garden room: an insulated garden room with walls of glass doors and windows. Planning and building regulations are the same as for any garden room.

Heat loss and overheating

Building regulations set a limit of 1.4 for new windows and 0.18 for new walls in an extension.⁷ Comparing those limits, a square metre of window lets out nearly eight times as much heat as a square metre of wall, and exempt glass rooms often do worse. So the more glass, the harder a room is to keep warm in winter.

Summer is the other problem. In a Which? survey of over 3,000 members, temperature was the most common conservatory regret, named by 24%, and Which? warns that floor-to-ceiling glass creates a greenhouse effect.⁴ To keep a glass room usable:

• Choose the right glass. Solar control glass with a low g-value lets in less of the sun's heat.⁸ It's usually specified for south-facing roofs, but it isn't standard on every model, so ask.⁵
• Plan for ventilation. South-facing rooms need more vents or opening windows.⁴ Ventilation panels also cut winter condensation.⁵
• Use blinds. Draw them as soon as the sun hits the room. Solar control film for an average conservatory roof costs around £1,000 fitted.⁹
• Think about the roof. Polycarbonate is cheaper but less thermally efficient and noisier in rain than glass.⁴

Planning permission

Attached glass rooms come under the same permitted development rules as other home extensions, and those rights apply to houses, not flats or maisonettes.¹ In England, a single-storey rear extension can usually be up to 3m deep (4m for a detached house) and 4m high, with eaves no higher than 3m within 2m of a boundary.¹⁰

Verandas are excluded from the extension permitted development rights², and the Planning Portal says they often need planning permission, especially if raised more than 0.3m off the ground or on the front of the house.³ Some suppliers say permission is rarely needed, but check with your council first.

Detached glazed garden rooms follow the outbuilding rules:

In England, a garden room usually doesn't need planning permission if it's single storey, behind the front of the house, has eaves no higher than 2.5m and an overall height of no more than 4m with a dual-pitched roof or 3m with any other roof, and, together with other buildings, covers no more than half the garden. If any part is within 2m of a boundary, the whole building must be no more than 2.5m tall.¹¹¹² These rights apply to houses, not flats or maisonettes. Rules differ in Scotland, Wales and Northern Ireland. Our planning guide covers the details.

Building regulations

In England and Wales, an attached glass room or conservatory is normally exempt from building regulations if it is single storey, at ground level, under 30m², separated from the house by external-quality walls, doors or windows, and has its own heating with separate controls. Its glazing and any fixed electrics must still meet the regulations.¹³ If you extend the house's heating into it, or remove the wall or doors between them, the exemption is lost.⁷¹³

Safety glass is required in "critical locations": glass in doors within 1500mm of the floor, glass within 300mm of the edge of a door and within 1500mm of the floor, and any other glass within 800mm of the floor.¹⁴

For detached garden rooms, see our building regulations guide.

What glass rooms cost

For a detached, glazed garden room, start with our cost guide and add the cost of the extra glazing you want.

Questions people ask

Does a glass room need planning permission?

An attached glass room is treated as an extension, so it can often be built under permitted development if it meets the size limits.¹ Verandas often need permission.³

How much does a glass room cost?

Glass extensions cost about £3,000 per m², averaging about £40,000.¹⁶ Small veranda kits start at £1,000 to £2,000.⁵

How do I stop a glass room overheating?

Use solar control glass with a low g-value, add vents or opening windows, and draw blinds when the sun hits it.⁸⁴⁹

Related guides

Sources

1. Planning Portal, Conservatories: planning permission.
2. legislation.gov.uk, GPDO 2015, Schedule 2, Part 1, Class A.
3. Planning Portal, Do I need planning permission to erect a veranda?.
4. Which?, April 2026, Conservatories: common pitfalls.
5. Grand Designs Magazine, June 2025, Glass verandas and glass rooms.
6. Which?, May 2026, How to buy the best garden room.
7. HM Government, Approved Document L, Volume 1: Dwellings (2021 edition incorporating 2023 amendments).
8. Pilkington (glass manufacturer), Solving the overheating problem.
9. Which?, June 2026, Four ways to stop your conservatory getting too hot or too cold.
10. Ministry of Housing, Communities and Local Government, Permitted development rights for householders: technical guidance.
11. Planning Portal (England), Outbuildings: mini guide. Permitted development limits for outbuildings.
12. legislation.gov.uk, GPDO 2015, Schedule 2, Part 1, Class E.
13. Planning Portal, Conservatories: building regulations.
14. Lancaster City Council Building Control, based on Approved Document K, Safety glass: where is it needed?.
15. MyBuilder, Aug 2026, Conservatory cost.
16. MyJobQuote, Sept 2026, Glass room extension cost.