Home extensions
Home extension drawings
An extension adds floor space to the house. The usual forms are a rear extension, a side extension, a wraparound and a two-storey extension. Planning drawings, building regulations drawings and structural calculations are three separate stages of that work.
Usual options
One new floor at the rear or the side, with its own roof.
The new floor turns the corner, along the rear and the side. Shown here in plan.
New rooms on both floors. This more often needs a planning application.
The outlines are general. A side extension can be a simple infill, or part of a wraparound. The right arrangement depends on the house and the space you need.
What the council usually asks for
Some rear extensions may be permitted development. Larger ones, and many two-storey extensions, need a planning application. Some larger single-storey rear extensions use a neighbour-consultation prior approval. The limits depend on the house, including whether permitted development rights still exist. The Planning Portal extension guidance is the place to check. A Lawful Development Certificate can confirm a permitted development scheme.
A householder application usually needs existing and proposed plans and elevations, and a location plan. The Planning Portal describes householder consent. The council’s validation list decides the exact drawings, and the council makes the planning decision. Party wall matters and specialist surveys sit outside the planning drawings.
Planning, building regulations and calculations
An extension is checked in three separate ways.
- Planning applications ask the council for permission. The permitted development and certificate route applies when the extension meets the limits for that house.
- Building regulations drawings show how the agreed extension is built. This approval normally applies when the extension is built, including where the planning route was permitted development. The rules are on GOV.UK.
- Structural calculations size the beams, lintels and roof the opening needs. They are a separate stage from the planning drawings.
Common questions
Is a side extension treated the same as a rear extension?
The drawing stages are the same kinds of stages. The planning route depends on the size, the position and whether the house still has permitted development rights. A wraparound or a two-storey extension is assessed from the house itself.
Can the later drawings follow plans that already exist?
Yes. Building regulations drawings and structural calculations can be prepared from an agreed set of planning drawings, including drawings prepared by someone else.
Which drawing do I need first?
Most homeowners start with the planning drawings, so the size and appearance are clear. Building regulations drawings and structural calculations follow for the design that is going to be built. The order can change if you already have planning consent.
See what drawings a house extension can need.
Request an extension quote