Semi-Detached Houses in the UK: a quick guide

What a semi-detached is, what to know about the party wall, and how Offrly values one.

What a semi-detached is

A semi-detached house is half of a pair of homes built together, sharing one wall, called the party wall, with a neighbour. Everything else, including garden, front door, driveway and roof, is individual to the property. Semi-detached is a very common UK property type.

What you typically get with a semi

• More space and garden than a terrace in most cases.
• A front and back garden in most cases.
• Often a driveway or at least the option of off-street parking.
• Side-return potential for extensions, where there is side access.

Things people commonly check

• Party wall. Noise transfer is property-specific. Varies by build age and materials.
• Roof line. In period semis the roof sometimes spans both halves.
• Extensions and neighbouring extensions. Can affect both the floorplan and future plans.
• Tenure. Most UK semis are freehold, but always confirm in the title.

How Offrly values a semi-detached

Offrly uses a proprietary ML model combined with AI photo analysis. The AI reads listing photos the way a seasoned property analyst would, and the model produces a point estimate. Enter a postcode and a few details on the valuation tab to try it.

Modelling extension and loft uplift on a semi

UK semis are the archetypal home that benefits from extending. The result card includes a Scenario Explorer — drag the bedroom slider up by one and the floor-area slider up by 20–30 m² for a typical loft conversion, or the floor-area slider up by 15–25 m² for a single-storey rear extension. The £ delta is the modelled uplift on your specific home against today's live UK comparable set.

Not a regulated valuation

Offrly produces an indicative market figure, not a regulated valuation. For mortgage, insurance or legal purposes, use a RICS-qualified surveyor.