What a garden annexe is for
- Guests or family who come to stay
- An older parent living close by
- A teenager who wants their own space
- A bedroom with a shower room and kitchenette
What drives the price of a garden annexe
A room someone sleeps in is the biggest step up.
What a garden annexe adds
- Building regulations sign-off for sleeping space
- Shower room or WC with drainage to the main sewer
- Kitchenette, more heating and often planning permission
What moves any garden room price
- Size and height
- Foundations: ground screws, pads or a slab
- Cladding and roof finish
- Amount and type of glazing
- Distance for power, water and drains
- Access: can materials reach the garden?
Typical price: from £39,000, fitted
Your written quotes show the real figure for your plot. See how garden room prices are built.
Planning and building regs for a garden annexe
- Permitted development does not cover an outbuilding used as a bedroom, bathroom or kitchen. That is "primary living accommodation".
- So an annexe someone sleeps in usually needs a planning application. Check with your council.
- Councils often approve annexes on the basis that they stay linked to the main house, not a separate home. Check with your council.
- Sleeping space removes the building regulations exemptions, so building control sign-off is needed at any size.
- A shower room or WC needs drainage, and new circuits are notifiable under Part P.
General guidance for England, not legal advice. Sources: Planning Portal outbuildings, GOV.UK technical guidance, Planning Portal building regulations. Checked 19 October 2026.
- Planning permission guide
- Garden room costs guide
- Building regulations guide
- Garden annexe rules guide
- Garden room sizes guide
- Foundations guide
- Insulation guide
- Cladding options guide
- Heating & air-con guide
- Electrics guide
- Near a boundary guide
- Conservation areas & Chilterns guide
- Green Belt guide
- Lawful development certificate guide
- Value, council tax & rates guide
- Choosing a builder guide
- Office vs extension vs loft guide
- Garden office tax guide
- Garden office internet guide
- Garden gym flooring guide
- Gym ventilation guide
- Soundproofing a studio guide
- Annexe for elderly parents guide
- Toilet or shower guide
- SIPs vs timber frame guide
- Bespoke vs flat-pack guide
- Garden room timeline guide
- Maintenance and lifespan guide
- Glazing and overheating guide
Garden annexes near you
We match you with builders who already work in your town. Pick yours for local planning notes.
Hertfordshire
- Garden annexes in Berkhamsted
- Garden annexes in Northchurch
- Garden annexes in Tring
- Garden annexes in Hemel Hempstead
- Garden annexes in Kings Langley
- Garden annexes in Harpenden
- Garden annexes in St Albans
- Garden annexes in Watford
- Garden annexes in Rickmansworth
- Garden annexes in Chorleywood
- Garden annexes in Bushey
- Garden annexes in Radlett
- Garden annexes in Borehamwood
- Garden annexes in Potters Bar
- Garden annexes in Hatfield
- Garden annexes in Welwyn Garden City
- Garden annexes in Welwyn
- Garden annexes in Hertford
- Garden annexes in Ware
- Garden annexes in Hitchin
- Garden annexes in Letchworth Garden City
- Garden annexes in Stevenage
- Garden annexes in Baldock
- Garden annexes in Bishop's Stortford
- Garden annexes in Hoddesdon
- Garden annexes in Cheshunt
Buckinghamshire
- Garden annexes in Chesham
- Garden annexes in Amersham
- Garden annexes in Great Missenden
- Garden annexes in Aylesbury
- Garden annexes in Beaconsfield
- Garden annexes in Gerrards Cross
- Garden annexes in High Wycombe
- Garden annexes in Marlow
- Garden annexes in Princes Risborough
- Garden annexes in Wendover
- Garden annexes in Buckingham
- Garden annexes in Little Chalfont
- Garden annexes in Chalfont St Giles
- Garden annexes in Chalfont St Peter
Garden annexes: questions people ask
Do I need planning permission for a garden annexe?
Usually, if anyone will sleep in it. Government guidance says permitted development for outbuildings does not cover primary living accommodation such as a bedroom, bathroom or kitchen. Ask your council or apply for a lawful development certificate if you are unsure.
Does a garden annexe need building regulations?
Yes, if it has sleeping accommodation. The floor area exemptions for outbuildings only apply when nobody sleeps in the building.
How much does a garden annexe cost?
Typical price: from £39,000, fitted, including VAT. Building regulations work, a shower room and its drainage, a kitchenette, heating and planning fees move the price most.
Can I rent out a garden annexe?
That depends on your planning permission and any conditions on it. Check with your council. Ask before you plan to let it.