Who is this plan for?
Thinking about extending your house and want to show the idea to an architect, a builder or the council before asking for quotes? This example shows the right way to draw an extension: start from the house as it is today, then add the new work on top, without erasing what's already there.
What's in the plan
The starting point is the detached house, 10 × 9 m: 82 m² on the ground floor, 82 m² upstairs. To the south of the kitchen, we add a 4 × 5 m extension (17 m² net), with a 3 m sliding door onto the garden and a window to the east. The ground floor grows to 99 m², the whole house to 181 m² of living space.
The plan uses the three colours of planning drawings:
- grey for the existing walls you keep;
- red for the walls to build (the extension);
- yellow for the wall to demolish: 3 m of external wall to knock through between the old kitchen and the extension.
The extension's dimensions are drawn separately, so its footprint is clear at a glance. The deck has moved west so it stays in front of the living room.
What works well
- Anyone can read it: a builder sees immediately what to build and what to take down.
- The wall to knock through is marked: it's often the most expensive part, with a lintel or a steel beam to plan for.
- The existing house stays accurate: if in doubt, you can compare with the original.
Ideas to adapt it
- Change the size of the extension: 3 × 4 m for a dining area, 5 × 6 m for a proper living space.
- Put it against the living room instead of the kitchen, or wrap it in an L around two walls.
- Replace the masonry extension with a conservatory or a timber frame.
- Check the distances to the boundary and to underground pipes before fixing the position.
Going further
The guide Plan an extension or conservatory walks through each step, from the first sketch to the brief for your architect. Before digging, find the pipes with Map of underground pipes and cables.