Should you build an annexe or a separate home?
An annexe is extra living space used as part of your existing home: the person living there shares the household, the garden and usually the services, and the annexe can’t normally be sold or let on its own. A separate home is a dwelling in its own right, with its own planning permission, and it can later have its own title, address and services.
A new separate home always needs planning permission, usually through a full or outline application. A self-contained annexe usually needs permission too, and councils often add a condition keeping it tied to the main house. Neither is the easy option in planning terms; they simply suit different plans.
Think about the long term. An annexe suits a family that expects to stay together on one property. A separate home gives more flexibility if circumstances change, because it could be sold or let later, but councils judge it as a new dwelling, with all the tests on access, privacy and garden space that come with that. In short:
- Annexe: used as part of the main household, usually tied to the house by planning condition, and not normally sold or let on its own
- Separate home: an independent household with its own planning permission, which can have its own title and be sold or let later
- Council tax: a self-contained annexe gets its own band, and a separate home always has its own
How will the council look at a home for family?
Councils judge the building on its planning merits. Who will live there rarely changes the outcome, because the home will outlast the current arrangement. That means the same questions as any garden plot: a safe and adequate way in, privacy and daylight for neighbours, enough garden for both homes, parking, bins, trees and drainage.
For an annexe, the council also looks at whether it genuinely works as part of the main home. A building with its own drive, its own garden fenced off and no link to the house may be treated as a separate dwelling, whatever it’s called on the drawings.
Who owns the new home, and who pays for it?
Families often pool money for a garden home: parents selling a house to fund it, or a grown-up child paying towards a home they’ll live in. That works best when everyone agrees in writing who owns what, what happens if someone wants to sell or move, and what happens on a death.
With a separate home, the plot can be transferred to the relative by a transfer of part, giving it its own title. If your house is mortgaged, the lender must agree to release the plot. With an annexe, the property usually stays as one title, so contributions are better recorded in a legal agreement. Each family member should take their own legal advice, and tax advice too, because gifts and transfers between relatives can have tax effects.
What costs should families plan for?
Beyond design and building, a few costs catch families out:
- Community Infrastructure Levy: where the council charges it, there are exemptions for self-build homes and for residential annexes, but each must be claimed before work starts
- Utilities: new connections for water, power and drainage, and sometimes a build-over agreement where a public sewer runs near the plot
- Structural warranty: if a mortgage lender will ever be involved, now or on a future sale, a new separate home usually needs a 10-year structural warranty or, for some lenders, an architect’s or surveyor’s certificate
- VAT and other taxes: the position differs between a new dwelling and an annexe, so take advice early
- Fire safety: in England, access for a fire engine, or other measures, often sprinklers, agreed with building control and the fire service if one can’t get close enough; in Wales, sprinklers in every new house
How do we design and build a home for your relative?
Through our design and build route, you keep the land and we design, get planning for and build the new home. We start with a free garden plot appraisal, then design around the person moving in: step-free routes, a ground-floor bedroom and bathroom if needed, and privacy for both households so living close doesn’t mean living on top of each other.
You receive a written quote after design and survey, and any guide price ranges are guides only. We handle the planning application and Building Regulations approval, and the council makes the planning decision. We’re a new brand within the S&K Group, so we expect you to ask questions and read everything carefully before you commit.
Common questions
Do I need planning permission for a granny annexe in my garden?
Usually, yes. A self-contained annexe with its own kitchen and bathroom generally needs planning permission, and councils often add a condition keeping it tied to the main house. A separate home always needs permission as a new dwelling. The council decides, and the use you describe needs to match how the building will really be lived in.
Can a family annexe be sold separately later?
Usually not, if planning permission ties it to the main house. To sell or let it on its own, you would normally need permission for it to become a separate dwelling, which the council judges like any new home. If you think you may want to sell separately one day, building a separate home from the start may suit you better.
Do we have to pay CIL on a home for a relative?
Only if the council charges the Community Infrastructure Levy. Where it does, there are exemptions for self-build homes and for residential annexes, but the claim must be made before work starts. Starting work before the exemption is confirmed can mean losing it, so it’s one of the first things we check.
Will an annexe have its own council tax bill?
A self-contained annexe is given its own council tax band. Discounts or exemptions may apply in some family situations, so check with your council once the annexe is planned. A separate home will always have its own band as an independent dwelling.
Can my son or daughter own the new home outright?
With a separate home, yes. The plot can be transferred by a transfer of part so it has its own title, with your lender’s agreement if your house is mortgaged. Gifts and transfers between family members can have tax effects, so each of you should take legal and tax advice before the transfer.