Guide
Drawings for a house extension
Most extensions are drawn in stages. The first set shows the council, or you, what is proposed. A later set shows the builder how the agreed extension is put together. Structural calculations sit with that later set when the design needs new beams, lintels or a new roof. You do not have to buy every stage on day one.
The planning set
This is normally the starting point when the size or the appearance still has to be agreed. It can include existing and proposed plans, elevations, a roof plan and a location plan. A single-storey planning pack starts from £1,050. A two-storey planning pack starts from £1,250. The fee for the drawings you need is confirmed in the quote.
Whether that set goes in as a planning application, or is used for permitted development, depends on the house. The Planning Portal extension pages describe the usual limits. A Lawful Development Certificate can confirm the planning position. It does not replace building regulations approval, and Tekneca does not guarantee a planning decision.
The building regulations set
This may be required before the extension is built, including where the planning route was permitted development. It is quoted for the agreed drawings and is not inside the £1,050 or £1,250 figures. The fee paid to the building control body is separate. Government guidance is on GOV.UK.
Structural calculations
These are normally required where a wall is opened up, a steel is added, or the new roof has to be designed. They may be a short set for a simple opening, or a wider set for a wraparound roof. Tekneca provides them for the agreed structure and prices them on their own. The sheets are issued for that project.
Common questions
Do I need all three before I speak to a builder?
A builder can often give a first idea from planning drawings. A price for construction, and the building control application, normally wait for the technical drawings and any calculations the design needs.
Is a two-storey extension treated the same as a single-storey one?
The drawing stages are the same kinds of stages. The planning route is more often a full application, and the structure is usually more involved. Both are confirmed for the house in question.
What if I already have planning drawings?
Send them with the address. Tekneca can quote the building regulations drawings, the structural calculations, or both, without repeating the planning set.
Service page: home extension drawings.
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