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Porch Building Regulations: When a New Porch Is Exempt, the Three Conditions That Keep It That Way, and When You Need Planning

Porch building regulations are mostly about what you must not change. A new porch built at ground level with a floor area under 30 square metres is exempt from the Building Regulations, as long as the front door between the house and the porch stays in place, the porch is not heated by the main heating system, and any glazing meets the safety glazing rules. Planning permission is a separate question with a much tighter limit: 3 square metres. Here is how both work, and the mistakes that turn a simple porch into a regulated extension.

The short answer

Why most porches are exempt from Building Regulations

Schedule 2 to the Building Regulations 2010 lists classes of exempt buildings. One of them is a porch or conservatory added at ground level with an internal floor area of less than 30 square metres, provided the glazing complies with the safety glazing requirements of Part K. Planning Portal guidance adds the conditions that keep the porch genuinely separate from the house: the existing external door, or an equivalent new one, must stay between the house and the porch, and the porch must not be served by the home’s fixed heating system.

The logic is thermal. Your front door and the wall around it are the boundary of the heated home. A porch outside that boundary is treated as an unheated lobby, so its walls and roof do not need to meet insulation standards.

The three catches that bring a porch under control

1. Taking out the front door

If you remove the door between the hall and the porch to make one open space, the porch becomes part of the house. It then needs Building Regulations approval like a small extension: insulation to current standards, structural sign-off and energy-efficiency calculations. This is the most common way an exempt porch becomes a notifiable one.

2. Extending the heating

Running a radiator from the central heating into the porch removes the exemption. A small independent heater with its own controls is a different case, but if you want a warm porch, ask your building control body before you build. Our radiator regulations guide explains the related rules.

3. Unsafe glazing

Porches are mostly glass, and Part K requires safety glazing in critical locations: in and around doors, and in low-level panes where people could fall or push against them. In practice that means toughened or laminated glass in the door and side panels and in any pane close to floor level. See our safety glass regulations guide for the zones.

Other rules that still apply to an exempt porch

• Electrics: new lighting circuits or sockets in the porch fall under Part P. Use a registered electrician who can self-certify. See Part P explained.
• Gas meters and flues: enclosing a meter box or building near a boiler flue needs care, since flues need clearances and meters need access. Check our boiler flue regulations page before you draw the footprint.
• Means of escape and access: do not make the route out of the house narrower or create a step that was not there before.
• Drains: a porch built over a public sewer or a manhole may need the water company’s agreement.

Planning permission: the 3 square metre rule

A porch is permitted development for a house in England (Class D of the General Permitted Development Order) if all of these are true:

• the ground floor area, measured externally, does not exceed 3 square metres;
• no part of it is more than 3 metres above ground level;
• no part of it is within 2 metres of any boundary of the house that adjoins a highway, which includes a footpath.

Three square metres is small, about 2m by 1.5m. Many porches that are well under the 30m² Building Regulations threshold are well over the planning limit. If yours is larger, or the house is close to the pavement, apply for householder planning permission. Permitted development does not apply to flats or maisonettes, and can be removed in conservation areas by an Article 4 direction, which is common in parts of London. For listed buildings you need listed building consent for almost any porch. See our guides to conservation areas and listed buildings.

Leaseholders

If you own a leasehold house or the ground-floor flat of a converted house, the front elevation usually belongs to the freeholder. You will need the freeholder’s consent under the lease, as well as planning permission. See licence to alter.

Practical design points

• Match the roof pitch and materials to the house; a porch is the first thing anyone sees.
• Allow room for the outer door to open fully without hitting the inner door, a pram or a bike.
• Plan for a coat hook, a bench and boot storage at the drawing stage, not afterwards.
• Leave the meter cupboard and any external tap accessible.

If you built a porch without approval and it was not exempt, a regularisation certificate can put it right before you sell. For the wider rules on alterations, see building regulations for renovations, or go back to the Vertigo Interiors homepage.

Sources: Building Regulations 2010, Schedule 2 (exempt buildings); Planning Portal, porches; GPDO 2015, Schedule 2 Part 1 (Class D).