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Conservatories, Extentions & Planning Permission: Your Guide

Conservatories and extensions are a beautiful and inexpensive way to enlarge your home. Conservatories have the added benefit of offering a panoramic view of the outdoors for a charming place to relax, work or dine. Before you purchase a DIY kit or begin building either an extension or conservatory, you should know the planning permission and building regulations you need.


Adding a conservatory is permitted development and does not need planning permission, subject to certain conditions and limits.

• The addition should cover no more than half of the area around the original house.
• No extension should be higher than the uppermost part of the original roof.
• No extension should be closer to a highway than the original house.
• A conservatory should extend beyond the wall of the original house by three metres or less for attached houses or four metres or less for detached houses.
• The height should be no more than four metres.
• Extensions over one storey should extend beyond the wall of the original house by three metres or less or be within seven metres of the back boundary.
• Eaves should be no higher than the existing house.
• Side extensions must have width less than half of the original house and height no more than four metres.
• Roof pitch over one storey should match original house.
• Verandas, raised platforms or balconies are not permitted.
• There is no permitted development for cladding the exterior, side extensions or rear extensions over one storey on designated land. Designated land includes national parks, World Heritage sites and Areas of Outstanding Beauty.

Building regulations also don’t apply to conservatories under certain conditions.

• If they are at ground level and do not exceed 30 square metres or floor area.
• If they have a heating system that is independent from the main house with separate power controls.
• No external walls, windows or doors were removed for entry into the conservatory. If they were removed, building regulations will apply.
• Electricity connections and glazing comply with any building regulations that are applicable.
• Conservatories should not block ladders or other escape routes from any room, loft or the roof.


Adding an extension is permitted development and does not need planning permission, subject to the same conditions and limits as stated above. Extensions of properties usually require approval under the Building Regulations. Extensions are exempt from the building regulations if they are a porch, conservatory, covered yard or path, or if they are a carport which is open on at least two sides with a floor area of less than 30 square feet. Any glazing needs to satisfy building regulation requirements.

Some of the building regulation requirements for certain extensions are:

• Foundations should be adequate to bear the load of the extension. This is usually concrete, but there are other types depending on the soil. A structural engineer will advise on the correct foundation.

• Flooring will need to support the contents of the room and, if it is a ground floor, it will need to be resistant to ground moisture and heat loss.

• Ventilation requirements depend on the type of extension. A new room should not inhibit the ventilation of any pre-existing room. If there is no open window, there should be a mechanical extract fan. There are regulations that determine the size of the fan for certain rooms.

• Structural openings that are made through existing external walls require regulation. If the opening is wider than the previous door, beams will need to be installed. Any added beams, steel or wooden, need to have sufficient fire resistance. Concrete beams, even with steel inside, are usually fire resistant.

• Walls that are partially below ground level are called substructure and need to be sufficiently strong to support the walls that are above the ground.

Other areas of an extension that are required to comply with building regulations are:

• Drainage and sewage pipes may need to change according to building regulations.
• Electrical work should be done by someone approved by a Building Control body.
• Doors and windows are subject to glazing, ventilation, heat loss, fire safety and means of escape regulations.
• External walls have building regulations for certain situations.
• Bathrooms and kitchens as part of a house extension need planning permission.
• Roofs have certain specifications that need planning permission.
• Internal walls, both load bearing and non-load bearing, have building regulations.

These guidelines are intended to give a basic idea of what will be required for someone to add a conservatory or extension to their home. They are not a definitive guide for legal information.

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