A porch outside an external door of a house can be permitted development where its external ground area is no more than 3m², its height is no more than 3m, and no part is within 2m of a curtilage boundary with a highway. Property-specific restrictions still need checking. [1]
What the three measurements mean
The planning test uses the ground area measured externally, not the usable space inside. For example, a rectangular footprint measuring 2m by 1.5m externally uses the full 3m² allowance. Wall thickness then reduces the internal space; it does not create extra permitted floor area. [1]
The distance test is to the relevant boundary with the highway, not simply to the kerb or the middle of the road. Show the house, porch and highway boundary on a measured plan, rather than estimating the distance from a photograph. The porch route can apply outside an external door other than the front entrance too. [2]
If a proposal exceeds a limit, reduce or reposition it, or investigate a planning application. Meeting the area limit alone does not compensate for failing the height or boundary test. [3]
Does the property have the right?
The householder porch allowance is not a flat or maisonette allowance. Check whether the building was created through a permitted-development route that excludes ordinary householder rights, and whether a planning condition or Article 4 direction removes the relevant right at the address. [2]
Listed status raises a separate issue. Alterations or extensions affecting a listed building's special architectural or historic character need listed building consent, regardless of whether the porch is small. Retaining an historic entrance or altering its surround should be assessed as part of the whole proposal. [4]
The building-regulations test is different
The statutory exemption covers a ground-level porch with floor area not exceeding 30m², subject to the applicable conditions. This does not increase the 3m² planning allowance. The two figures belong to different regimes. [5]
For that building-regulations exemption, the existing entrance door between house and porch must remain. Existing ramped or level access for disabled people must not be adversely affected. Glazing and fixed electrical installations still need to comply with the appropriate requirements. [6]
Removing the existing entrance door and incorporating the porch into the heated interior changes the proposal being assessed. Do not base the project on the exemption while designing away one of its conditions; obtain a building control assessment of the actual arrangement. [6]
What to settle before ordering
Prepare one coordinated drawing showing the external footprint, roof height, highway distance, retained entrance door and access arrangement. Record separately the conclusion on planning and the conclusion on building regulations. This makes clear whether the proposed design meets both tests, instead of using the word “exempt” without saying which test it refers to. [2] [6]
For uncertainty about the planning status of a specific design, a proposed Lawful Development Certificate is the formal route to establish lawfulness. It should address the porch actually intended, not a smaller outline design that will later be enlarged. [7]