There are several different types of Houses Extensions that may or may not be suitable for your house. There are Kitchen extensions, Side extensions or Rear extensions, Single storey extensions and two storey extensions. Occasionally an extension will be three or more stories in high. Deciding what type of Extension is suitable for your home is not always straightforward but once this is decided the conceptual and detailed design of your extension can be explored.
The main considerations to think about when considering an extension are the Planning restrictions and the Conceptual and detailed design of the extension. If you want to choose the right type of extension and get the best design you should always appoint a Qualified Architect who you can communicate effectively with.
The first step is to assess what can be built from the point of view of your Planning department.
If your house is not within a Conservation Area, has any Article 4 directions or has not previously had an Extension it will have permitted development rights. These rights are more generous these days because the Government wants to encourage development in order to bolster the economy. This together with the high cost of buying a new larger home is why there is a lot of extension work being done to private residential property in London and the surrounding counties. Another reason for the recent increase in residential extension development is the increasing proliferation of private landlords buying houses and extending them to accommodate more bedrooms so that they can increase the lettable income. Clearly this trend is closely tied to the United Kingdoms membership with the European Union and its global outlook which has promoted higher levels of immigration and an increased demand for housing. The Government has recently extended the relaxed permitted development rights until 2019.
The permitted development rights allow you to build 3m back from the main rear wall of your house without informing the council as long as the extension does not exceed 3m in height. For detached houses this is 4m. The Architectural design will show you the different possibilities. You may be unsure whether a flat roof or a pitched roof is more suitable for your house. The Architectural design will show you if the extension ceiling can be at the same level as the existing ceilings. The Architectural drawings will show you if the structural beams have to be expressed or preferably hidden within the ceiling so that you have a smooth continuous ceiling with light fitting recessed or hanging from it.
The Ceiling of the extension is as important to the design as the functionality of the layout. The Architectural design will ensure that the size, position and type of roof lights are suitable and that they coordinate with the interior rather than randomly penetrating the ceiling. It is always a good sign of properly co-ordinated and considered Architecture when elements such as Roof lights are well proportioned and located in relation to the room and when they line up with other internal elements such as kitchen island units, doors or windows.
The relaxed permitted development rights also enable you to extend from the main rear wall of you house by up to 6m. However, the council needs to be informed of anything beyond 3m by way of an application called a Notification for Prior Approval for a Proposed Larger Home Extension. Or what Architects call a Neighbour Consultation Scheme because it essentially means consulting with your neighbours about the extension and if no objections are made then it will be automatically approved.
If your extension needs to be higher than 3m or beyond 6m from the main rear wall then a Householder Planning application will be need to be submitted to your councils Planning department.
Planning Applications consist of the application forms, a Planning Design & Access statement, the existing and proposed drawings, the Community Infrastructure levy Form and the Fee. The Planning fee is currently £172.
Community Infrastructure Levy came into are lives in April 2010. It is generally not relevant to small development which do not exceed 100m2. With larger developments it allows local authorities in England and Wales to raise funds from developers undertaking new building projects in their area. The money can be used to fund a wide range of infrastructure that is needed as a result of development. This includes new or safer road schemes, flood defences, schools, hospitals and other health and social care facilities, park improvements, green spaces and leisure centres.
There are many Companies supplying Rooflights. Here is a small list:
Other considerations when thinking about an extension are the floor construction. If your current house has a suspended timber floor with a ventilated void below it then it is important that the extension maintains this ventilated void to the back of the house.
You should also decide if you want a step down into your garden or a level threshold so that the transition from inside to outside is continuous. This continuity can be improved by using the same type of floor finish inside and outside.
If the side walls of the extension are right up against the boundary line then you will need to decide if you want a rainwater gutter along this boundary which will not be very accessible. You may prefer a parapet wall or a flat roof sloping towards the garden. If the neighbour has already built an extension your extension may need to but up against it and the roofs may need to integrate.
These Boundary questions will be matter for both the Planning officer and the Party wall surveyor.
A PW Surveyor may insist on a parapet wall at the boundary in order to make it simpler for the neighbour to build an extension up against yours in the future. However a Planning officer may insist on a sloping roof without a parapet wall. In these situation where the Planning officer and the PW surveyor disagree the Planning officer’s preference is more important because the application would be refused otherwise. Clearly this is not an issue with permitted development extensions. It is the job of the Architect to coordinate between these different parties and make sure the extension is properly designed and gain legal consent from the planning department.
Once Planning permission has been granted it will be time to make sure the drawings are detailed enough so that the builder knows how to build the extension.
The structural design will be carried out which will show the position and size of steelwork and timberwork. The design will show the thickness of the concrete floor slab construction and the depth and type of foundations.
The position of mechanical ventilation should be shown on the drawings. The continuity of existing ventilated floor voids will be shown.
The type and thickness of floor, wall and roof insulation will be shown on the drawings.
The routing of new and existing effected surface and foul drainage will be shown on the Architectural drawings. If the extension is within 3m of a public drain then a Build Over Agreement application will need to be submitted to your Water Authority.
The type and extent of finishes for the floors, walls and ceilings will be shown.