Single Storey or Double Storey Extension: Which Is Right for Your Home?

Quick Comparison

Factor	Single Storey	Double Storey
Typical cost (Wolverhampton)	£35k–£65k	£55k–£95k
Planning permission	Often permitted development	Usually needs full application
Disruption	Ground floor only	Two floors, longer build
Value added	~5–10%	~10–20%
Best for	Kitchen, dining, living space	Extra bedrooms + bathrooms

Single Storey Extensions

Pros: Often permitted development (up to 3m/4m rear, or 6m/8m with prior approval). Less disruptive. Lower cost. Ideal for open-plan kitchen-diners, utility rooms or ground-floor bedrooms.

Cons: Only adds ground-floor space. Limited roof light options unless you add lanterns/skylights.

Double Storey Extensions

Pros: Doubles the floor area for less than double the cost. Adds bedrooms and bathrooms upstairs — huge value boost. Better roof light potential.

Cons: Almost always needs full planning permission. More disruptive (two floors). Structural work more complex (steels, foundations). Neighbour impact assessments often required.

Side Return & Wrap-Around Extensions

If you have a side alley, a side return (single storey) or wrap-around (L-shaped) can be more practical than a deep rear extension, bringing light into the centre of the home.

Permitted Development Limits (2026)

• Single storey rear: 3m (terraced/semi) or 4m (detached) — up to 6m/8m with prior approval
• Double storey: NOT permitted development — always needs full planning
• Side extensions: up to half the width of the original house
• Materials must match existing

Conservation areas and Article 4 directions tighten these rules. 5K Construction checks your property before quoting.