Prepare for oversized extensions as planning rules set to change

Last week's news about the proposed relaxation of planning rules has produced a wealth of mixed reactions. It might have come as a relief for those homeowners who tried unsuccessfully to gain planning permission in the past; on the other hand some people will worry about their neighbours' grand plans and the potential effect on their amenities.

The proposed changes will concern single storey rear extensions only, so for other types of improvements such as side, first floor and loft extensions the current regime will remain in place.  Apparently Conservation Areas are to be excluded from the planning relaxation.

Rear extensions are already Permitted Developments, provided  they don't project more than 3 meters from the (original) rear wall of the house. The government is proposing to increase the depth of a Permitted extension to 6 meters on terrace and semi detached houses, and to 8 meters on detached properties.

Whilst this is certainly good news for some potential improvers, a 6 meter long extension is an opportunity that should be planned carefully.

In terraced houses for example there is a real risk of "tunnelling" effect, i.e. creating a long and narrow space with light at one end only. Since there is a relationship between the height of the roof eaves and window head, the orientation of the facade and the depth to which natural light will penetrate into a room. The fenestration should be designed to optimise daylight as well as views.

The original rear reception room might end up 'landlocked' and dark to the extent that it is no longer desirable as a living space: an increase in floor area does not necessarily equates to increased living area. Maybe this space could be turned into a utility room, which will involves the remodelling of the overall layout.

Increased Permitted Development rights also raise additional "technical" issues such as party walls and drainage.  The majority of terraced houses range in width (internally) from less than 4 meters to about 6.5 meters;  to avoid long and narrow spaces it is useful to build astride the boundary (party) line, which necessitates neighbours' agreements and careful detailing of the construction junctions. Discharge of rain and waste water from a large rear extension is also potentially difficult since house drains tend to connect with existing sewers at the rear, in which case they need to be diverted as part of the construction work.

In all but the simplest extensions the final design has to be developed to incorporate technical constraints, the client's brief and budget and the site specifics: this is where architects' ingenuity can make a difference.

Dittrich Hudson Vasetti architects in Bristol have in-depth experience of domestic projects and look forward to assist their clients on home extensions and alterations.