Property types
Creating a floor plan for a semi-detached house
A semi-detached house sits between a terrace and a detached house, and the plan has to show exactly that. It has three free elevations, one shared wall and normally its own plot with its own access.
Because the two halves are often built as mirror images, plans belonging to the wrong side circulate constantly. A mirrored plan looks right at first glance and reliably confuses people at the viewing. Always check the entrance position against reality.
What separates a semi from a terraced house
The practical difference is the third window elevation. A mid-terrace is lit from front and back only; a semi is also lit from the side. That changes the layout fundamentally: bathrooms and stairwells can move to an external wall instead of sitting in the core.
Draw every window on the free elevation, including small ones. The plan then makes visible why the property is valued differently from a terrace on the same street.
Drawing the party wall correctly
The shared wall is a party wall: twin-leaf, clearly thicker than any internal partition and in almost all cases not alterable. Show it at a realistic thickness and mark the side where the neighbouring half adjoins.
That answers two questions that come up at every viewing: how good is the sound insulation, and can the wall be opened up? A plan that draws the party wall like a normal partition raises hopes that cannot be met.
- Party wall at realistic thickness, clearly marked
- Show the entrance side correctly — never mirror it
- Draw all windows on the free elevation
- Assign terrace, carport and garden share to your own half
Areas and outdoor space
Living area follows the same rules as a detached house: cellars and garages stay out, converted lofts are weighted by clear height, terraces normally count at a quarter.
One argument is specific to semis: the garden share. It is not living area but it belongs in the listing. Keep it separate in the text and show only the areas adjoining the building on the plan, so the numbers do not blur together.
Frequently asked questions
Is the neighbour's plan simply a mirror image?
Often, but not always. Developers mirror the shell, yet fit-outs, extensions and later alterations frequently differ. Never use a mirrored neighbour plan as a substitute for surveying the unit you are selling.
How should I show the shared wall?
As a party wall at its true thickness, clearly heavier than internal walls, with a note pointing to the neighbouring side. That explains the acoustics and the gap between external size and living area.
Does the garden share belong in the area figure?
Not in living area. Plot and garden areas are stated separately. On the plan it is usually enough to show the terrace and the immediately adjoining surfaces; the text covers the rest.