The limits
| Rule | Limit | Source |
|---|---|---|
| Ground area | No more than 3 m², measured externally | D.1(b) |
| Height | No part more than 3 m above ground level | D.1(c) |
| Distance from a highway | No part within 2 m of any boundary of the curtilage with a highway | D.1(d) |
| Type of house | Not a house created by a permitted change of use under Part 3, or built under Part 20 | D.1(a), (e) |
Class D covers "the erection or construction of a porch outside any external door of a dwellinghouse" (para D), so it can be at the front, side or back. It has no conditions on materials, and no extra limits on article 2(3) land, which includes conservation areas.
Measuring a porch
The 3 m² is the ground area measured on the outside of the structure, so wall thickness counts. As a hypothetical example, a porch 2 m wide and 1.5 m deep on the outside has a ground area of 3 m², which is right at the limit; at 2.1 m wide it would be 3.15 m² and over it. Height is measured from the ground next to the building, using the highest part of the ground where it slopes (art 2(2)).
The 2 m rule
No part of the porch may be within 2 m of a boundary of the curtilage with a highway (D.1(d)). For Part 1, "highway" includes an unadopted street or a private way (para I). The Order does not say whether exactly 2 m counts as "within 2 metres", so keep a margin.
Bigger than a porch
Anything larger at the front is not a porch under Class D, and Class A does not cover an extension beyond the principal elevation of the original house (A.1(e)(i)). A front extension therefore needs a planning application, at a council fee of £548 for one house from 1 April 2026. For extensions at the back or side, see rear extensions and side extensions.
Other things that can remove the right
- Flats and maisonettes have no Part 1 rights, because a "dwellinghouse" does not include a building containing flats (art 2(1)).
- A condition on an earlier planning permission (art 3(4)).
- An Article 4 direction that removes Class D for an area or for particular development (art 4).
- A listed home needs listed building consent for works affecting its character (LBCA 1990 s7); see our listed building check.
A February 2024 government consultation proposed changes to householder rights, but GOV.UK still says "We are analysing your feedback", so the current limits stand.
What the free check tells you
The free check tests your plot outline against the Article 4 directions your council publishes and looks for list entries on your plot, then shows the porch limits. Where your council does not publish its Article 4 data, it says so instead of reporting none. It does not measure the distance to your front boundary.
For certainty: a Lawful Development Certificate
A porch is a small job, but if you want certainty, for example before selling, apply to your council for a Lawful Development Certificate for proposed works (TCPA 1990 s192). The council fee is half the full application fee, so £274 on a £548 householder fee, and the decision is due within 8 weeks of a valid application. See Lawful Development Certificates and planning fees 2026.