Why two storeys costs less per square metre
Foundations, scaffolding, roof structure and site setup are largely fixed costs. Adding a first floor over the same footprint spreads them across twice the floor area, so the second storey typically costs noticeably less per square metre than the first.
Common layouts
The most requested arrangement is a master bedroom with en-suite above, and an enlarged kitchen-diner or utility below. Side infills over a driveway are popular on 1930s semis; rear returns suit larger detached properties.
- Master bedroom with en-suite above, kitchen-diner below
- Bedroom over a new utility and boot room
- Side and rear return combined into an L-shape
- Contemporary clad upper floor over full-width glazing
Planning permission
Two-storey extensions are far more likely to need a full planning application than single storey work. Councils look closely at the impact on neighbouring windows, the distance to the boundary, and whether the roof and materials are subordinate to the original house. We design to those tests from the first sketch rather than discovering them at the planning approval stage.
Party wall and structure
Semi-detached and terraced properties can usually trigger the Party Wall Act 1996 for excavation near the shared wall. Structurally, a two-storey extension needs engineered foundations, floor joist design and steelwork at both levels. We deal with all these matters as part of our fixed price.
Programme
Expect 16–22 weeks on site. First-floor work adds scaffolding, a roof tie-in and a first-fix trade sequence that cannot be compressed, so we build the programme around a realistic weather allowance for the North West.
Frequently asked questions
How much does a double storey extension cost?
We detail prices for a two storey extension on our website because we like customers to have a solid idea of what it's likely to cost. Optional upgrades such as bifold doors, solar control glazing, external timber cladding finishes etc are clearly set out within our brochure.
Will a double storey extension add value?
Adding a bedroom and bathroom is generally the strongest value move available to a family home, particularly where it takes a 2 bedroom home to 3 bed or a 3 bedroom house to a 4 bed.
Do I need to move out?
Usually not, though the week the first-floor opening is formed is disruptive. We plan that stage with you in advance.