Tips for a Successful Loft Conversion

Financial feasibility

See our previous blog for advice.

Planning

Most loft conversions can be done using permitted development rights which allows added roof volume behind the front roof slope plane of up to 40m3 for terrace houses and up to 50m3 for semi or detached houses. Exceptions are flats, houses in conservation areas and listed houses. For these, planning permission is required, and local authority planning policy is generally more restrictive in terms of the size of roof extensions allowed. However, where there are numerous examples of large, permitted development roof extensions in the vicinity, planning permission for similar may be granted of the basis of precedent. Balconies are not allowed under permitted development and seldom under planning permission, however Juliet balconies are allowed.

Building regulations

The key building regulation for loft extension design is the clearance required above stairs which is at least 2m generally or 1.8m with a ceiling sloping perpendicular to the stairs. Increased roof and floor build-up from structural strengthening and insulating must be factored in, because permitted development doesn’t allow any roof extension higher than the original roof ridge. However, planning permission to raise the ridge up to 20cm is sometimes approved for terrace houses with parapet party walls or for detached houses.

The loft floor will need strengthening with steel beams and floor joists while the roof ridge will require a steel beam to compensate for the removal of existing timber roof struts. This new structure must be calculated by a structural engineer.

Means of fire egress is also an important consideration as it informs the layout. Normally when converting a loft which will become the second floor of the house, all doors off the hallway on the ground and first floor must be upgraded or replaced if not fire resistant. The loft room must also be separated from the rear of the house with a fireproof door. If the stairs are open plan on the ground floor, then mist sprinklers will be required.

Party wall consent

To support the steel beams, pockets will need cutting into the party wall(s), and this requires party wall consent from your neighbour(s). If they won’t sign template letters which can be found in the party wall explanatory booklet, you will have to hire a party wall surveyor or an extra one for each neighbour if they request.

Roof extensions

Permitted development normally allows the extension of a hip ended roof (a side facing roof slope) to form a gable (a side facing triangular wall) which is often crucial to allow new stairs above existing, and to accommodate a large rear dormer (a flat roofed extension of the rear roof slope). The latter increases the ceiling height and usable floor area in the loft, and accommodates a bathroom where full height is required above the shower, basin, and toilet.

Roof windows

The insertion of roof windows into any roof slope is normally permitted development provided those which face sideways are more than 1.7m above floor level or are opaque glazed and permanently fixed shut. They are typically installed in the front roof slope (where roof extensions are forbidden) to give light and cross ventilation to the bedroom or stairs.

Hiring a builder

See our previous blog for advice.