An extension creates new floor area beyond the existing footprint. A loft conversion turns roof space into usable accommodation. The better route depends on the room you need, available land and headroom, structural feasibility, planning constraints, access and budget.
Why consider an extension?
Ground-floor extensions can suit kitchens, dining rooms, utility spaces and accessible living. They affect the garden, foundations, drainage, external walls and openings. Quotes should distinguish the shell from glazing, electrics, plumbing, heating, flooring, decoration and kitchen supply.
Why consider a loft conversion?
A loft can add bedrooms, a study or bathroom without using garden space. Feasibility depends on roof form, usable height, staircase position, structure, fire precautions and services. Attractive concept images are not a substitute for checking those constraints.
Compare the whole project
Obtain appropriate design and structural advice. Confirm planning or lawful-development position, building-control route, party-wall implications, temporary protection, waste, scaffolding and who coordinates each trade. Compare specifications and exclusions rather than cost per square metre alone.
See LP10 building services or send a multi-trade building enquiry.
Score both options against the room you need
Write a brief covering room purpose, minimum usable size, accessibility, daylight, storage and the relationship to existing spaces. An extension often works best when the new space must connect to a kitchen, garden or ground-floor living area. A loft conversion can preserve the garden and suit bedrooms or a study, but usable headroom, roof structure, stair position and fire strategy can rule out an attractive sketch. Compare net usable space after walls, slopes, stairs and circulation—not just headline floor area.
Surveys and enabling work
Extensions can uncover drainage, weak ground, shared sewers, buried services and constraints at boundaries. Loft work can reveal non-standard trusses, undersized ceilings, difficult steel routes, water tanks or limited escape options. Both can affect electrics, heating, ventilation and alarms. Before seeking a fixed construction price, develop enough design, structural and specification information for bidders to price the same result. Clarify planning status, building-control route and any party-wall or neighbour access issues for the actual property.
Questions for comparable building quotations
- Which drawings and specification form the basis of your price?
- What design, approvals, inspections and structural work are included?
- Which foundations, drainage, steelwork, stairs and roof elements are provisional?
- Does the scope include electrics, plumbing, heating, plastering and decoration?
- How will the occupied home be protected and kept secure and weather-tight?
- Who coordinates changes, records approvals and prices variations?
An architect or designer, structural engineer and building-control body may be involved before and during construction. Builders then coordinate specialists such as electricians, plumbers, heating engineers, roofers, scaffolders, window installers, plasterers and decorators. Party-wall surveying or drainage advice may also be required; it should not be assumed that the builder alone provides every professional role.
Explore the LP10 building-services hub, then request a multi-trade project quote once the brief and available documents are ready.