Garden annexe for elderly parents: planning, council tax and care

What a granny annexe is

It is a self-contained building in your garden, with a bedroom, a shower room and a kitchenette or kitchen. A parent or relative lives in it. It is part of your home, not a separate house. Our garden annexe rules guide covers the basics.

Planning permission

Government technical guidance says permitted development for outbuildings does not cover primary living accommodation such as a bedroom, bathroom or kitchen. The Planning Portal says the outbuilding rules do not cover use as separate, self-contained living accommodation.

So an annexe sits outside permitted development in most cases. You will usually need a planning application. Ask your council early. A lawful development certificate is an optional decision that confirms whether a proposal is lawful. It is a way to check before you commit.

Councils often grant permission on the basis that the annexe stays ancillary to the main house. Conditions may say it cannot be sold or let separately. Read them before you sign off a design.

Listed buildings, conservation areas and National Landscapes add limits. See garden room planning permission.

Building regulations

The small-outbuilding exemptions apply only to buildings with no sleeping accommodation. An annexe has a bedroom, so it needs building regulations approval at any size. See building regulations for garden rooms.

Building control will look at structure, fire safety, insulation, ventilation, drainage, electrics and more. Electrical work must follow Part P. A toilet or shower needs drains. See garden room with a toilet or shower.

Council tax

Council tax on an annexe depends on how it is banded and who lives there.

• Dacorum Borough Council lists an exemption for an annexe or similar self-contained part of a property that is separately banded and occupied by a relative over 65 or a disabled relative.
• Dacorum says this is not applied for online. You phone the council.
• Other councils word their rules in their own way. Some offer a discount instead. Check with your own council before you build.

If the annexe is banded separately, it may get its own bill. If your parent does not meet the exemption, ask about discounts. Do not assume. Ask the Valuation Office Agency and your council how a new annexe will be treated.

Care needs and design

Think about what your parent needs now and in ten years.

• A level entrance. No steps, or a ramp that is easy to use.
• Wide doors. Room to turn a walker or a wheelchair.
• A level-access shower. A wet room is safer than a bath.
• Easy heating and lighting controls.
• A clear path from the house. Lit, even and non-slip.
• An alarm or call system.

Ask your builder to show you the layout with these in mind. Tell them about future needs early. It is easier to design in than to alter later.

Grants for adaptations

GOV.UK says you could get a Disabled Facilities Grant from your council if you are disabled and need to make changes to your home. Conditions include physical or learning disabilities, age-related needs, autism, dementia, progressive or terminal illness and mental health conditions. Covered work includes wider doors, ramps, grab rails, level-access showers and extensions such as a ground-floor bedroom.

The eligibility page says the council must agree that the work is necessary and appropriate for the disabled person's needs, and reasonable and feasible given the property. Starting work before the council approves may mean you get no grant. Planning permission and building regulations are applied for separately. The applicant must be the owner, tenant or landlord.

Whether a grant can go toward a separate garden building is for the council to say. Ask before you spend.

Talk it through as a family

• Who pays, and who owns what?
• What happens if your parent needs more care?
• What happens to the annexe in the future?
• Could the family tax or inheritance position change?

For legal and tax questions, ask a solicitor or financial adviser. We cannot advise on them.

Cost

Annexes have the most to price: groundworks, drains, a shower room, a kitchenette, heating and fees. We do not give prices here. Use the garden room cost calculator and read garden room costs.

Annexes in Herts and Bucks

Each council applies its own policies. In Berkhamsted, Tring and Hemel Hempstead that is Dacorum Borough Council. In St Albans and Harpenden it is St Albans City and District Council. In Amersham, Chesham and Aylesbury it is Buckinghamshire Council. Also see garden offices if the room may change use later.

Steps to take

• List your parent's needs now and later.
• Talk to your council about planning and council tax.
• If a grant is possible, apply before work starts.
• Get quotes that include planning drawings, building control and drainage.