Granny annexe cost: planning a complete living space

Price the accommodation, not the label

A room for occasional visits and accommodation for a relative living independently are different briefs. Sleeping, bathing, cooking, laundry and storage each need provision. A private bathroom or kitchen changes plumbing and ventilation as well as the visible fittings. Write down the daily activities the annexe must support before deciding its floor area, and show furniture on the plan to test how the space will work.

Garden annexe prices cannot be compared meaningfully unless those facilities are defined. One proposal may include a bathroom and fitted kitchen while another ends at plastered walls. Decide who supplies appliances, cabinetry and sanitaryware, and name the level of finish. The accommodation schedule then becomes a practical basis for comparing builders rather than relying on a general description such as self-contained.

Separate the main parts of the quote

Ground and service routes create different budgets

The plot affects the foundation design before the external appearance is chosen. Soil, levels, trees, existing structures and drainage may require investigation or a different support solution. A sloping or constrained garden is not equivalent to a clear level site. Ask what information supports the foundation allowance and how the quote treats additional work revealed during excavation.

Service connections should be traced on the site plan. A bathroom needs a workable foul-drainage route, while water, electricity and heating arrangements must suit the intended occupation. Crossing a drive or working around an existing extension adds excavation and reinstatement. Clarify whether existing capacity needs assessment and whether the quote covers the complete routes, testing and making good, not just connections inside the new building.

Accessible design changes the specification

An entrance that is convenient now may become difficult if mobility changes. Discuss the route from the house, threshold levels and enough circulation around furniture. Door widths, bathroom layout and space for assistance need consideration before the drawings are settled. Accessibility should follow the intended occupants, not a generic list of features added after the room has been designed.

These decisions can affect floor area, doors, fittings and external works. A level threshold must also be detailed against rainwater entry. Positions for switches, handles and potential grab-rail fixings deserve attention alongside the visible finishes. Agree which adaptations are included now and which are being allowed for later so the quote represents the accommodation you actually need.

Intended use and approvals belong in the budget

An ancillary annexe connected in use to the main home is different from a dwelling intended to function independently. The property, facilities, access and proposed occupation all matter. The word annexe does not itself establish a permitted development route or remove the need for permission. Explain the intended arrangement accurately when seeking planning advice.

Planning and building regulations are separate checks. Drawings, structural design and any necessary approvals may affect the programme and specification before the construction quote is settled. Confirm who provides this information and which fees or professional work sit outside the building scope. A changed layout or approval condition may change the work, so compare proposals based on the same agreed design.

Ask these questions before comparing totals

• Is the price for a shell or complete living accommodation?
• Are connection routes and any existing-service upgrades identified?
• Which kitchen, bathroom and floor finishes are specified?
• Does the scope include accessible paths and making good in the garden?
• How are concealed ground conditions and provisional items handled?
• Who supplies drawings, approvals and completion information?

From a room list to a useful written proposal

Collect photographs, available property plans and the occupants’ main requirements before a site visit. Include the rooms, facilities and access needs you expect, and identify whether the annexe is connected or detached. The builder can then assess the design alongside ground levels, delivery access and service routes instead of assuming a standard garden building.

Granny annexe prices should be read alongside the exclusions, specification and programme. A lower total may leave paths, decoration or utility work for a separate stage. For the building scope, see our granny annexe service below and arrange a free site visit. Comparing complete written proposals makes it easier to prioritise the accommodation without losing sight of essential connections and finishing work.