The first question most families ask is simple: will an annexe fit in our garden? The good news is that most UK gardens can accommodate a granny annexe. You don't need acres of space. A comfortable one-bedroom annexe requires a footprint of just 50 to 60 square metres, smaller than many garden sheds you see in suburban gardens. Let's explore the real requirements and how to assess your space.
Minimum Garden Size
You might be surprised how little space is needed. Here are typical footprints:
- Studio annexe: 30 to 40 square metres (roughly 6m x 6m)
- One-bedroom annexe: 45 to 55 square metres (roughly 8m x 6m)
- Two-bedroom annexe: 55 to 70 square metres (roughly 10m x 6m)
- Plus access paths and outdoor space around the annexe
- Total area needed: typically 1.5 to 2 times the footprint
- Many standard suburban gardens easily accommodate these sizes
The 50% Rule
Under permitted development rules, outbuildings (including annexes) cannot cover more than 50% of your garden. This is calculated as:
- Total garden area (excluding the footprint of your original house)
- Minus area already covered by sheds, garages, extensions, etc.
- The remaining area available must be at least double the annexe footprint
- Most gardens easily meet this requirement
- If your garden already has many structures, you may need to remove some
Position Considerations
Where in your garden the annexe can go depends on several factors:
- Cannot be forward of the principal elevation (front of your house)
- Height restrictions increase if closer than 2m to boundary
- Consider overlooking: avoid windows directly facing neighbours
- Think about privacy for both annexe occupant and main house
- South-facing orientation maximises natural light and solar gain
- Consider garden use after installation: preserve patio, play areas if possible
Access for Delivery
This is often the biggest constraint. Your annexe arrives by truck and crane, which need access:
- Ideal access: Side gate or passage at least 3m wide direct to garden
- Workable access: Lifting over the house is possible in some situations
- Minimum crane positioning: Hard standing area adjacent to garden
- Road access: Low-loader trucks need space to park (temporary permits available)
- Overhead obstacles: Power lines, trees, and roof overhangs affect crane reach
- We assess access during our free site survey and advise on solutions
Utility Connections
Your annexe needs connection to mains electric and water:
- Electric: Connection to your existing consumer unit or separate supply
- Water: Branch from your existing mains supply
- Drainage: Connection to existing drains or new soakaway
- Distance matters: Long runs increase cost (typically £100 to £150 per metre)
- Ideal position: Close to the house minimises connection costs
- We handle all utility connections as part of our service
Ground Conditions
The type of ground affects preparation requirements:
- Level ground: Minimal preparation, lowest cost
- Sloping sites: Can be accommodated with stepped bases or retaining
- Clay soil: May need specific drainage solutions
- High water table: Additional waterproofing for base
- Trees nearby: Root protection and foundation design considerations
- Previous structures: Existing bases can sometimes be reused
Common Obstacles (That Can Be Overcome)
Don't assume your garden won't work. These issues have solutions:
- Narrow side access: Smaller sections can navigate tighter spaces
- Trees in the way: Professional arborists can lift crowns or carefully remove
- Sloping ground: Our designs adapt to gradients up to 1 in 10
- Overhead cables: Utility companies can temporarily relocate for a fee
- Existing structures: Sheds and greenhouses can be relocated or removed
- Limited crane access: Specialist equipment reaches over buildings when needed
Neighbour Considerations
Good neighbour relations matter, even when planning permission isn't required:
- Discuss your plans before building. Surprises breed objections
- Consider their view: Position windows sensitively
- Minimise overshadowing: Keep away from boundaries where practical
- Construction disruption: Warn neighbours about delivery day, crane etc.
- If neighbours object after building starts, it's much harder to resolve
- Most neighbours are supportive when approached respectfully
Legal Restrictions to Check
Before proceeding, verify these potential legal issues:
- Restrictive covenants: Your property deeds may restrict outbuildings
- Leasehold: Freeholder permission may be required
- Conservation area: Stricter rules apply, but annexes often still possible
- Listed building curtilage: Special consent likely needed
- Tree Preservation Orders: May limit where you can build
- Rights of way: Check boundaries and access rights carefully
What About Flats or Houses with No Garden?
Unfortunately, an annexe needs land. If you live in a flat or have no garden:
- An annexe isn't possible on your property
- Consider whether family members with gardens could host the annexe
- Some families build on a parent's property rather than their own
- Land adjacent to your property could potentially be purchased
- These situations need creative thinking and family discussion
The Free Site Survey
The best way to know if an annexe will fit is a professional site survey. Our surveys are free and include:
- Measurement of available space and positions
- Assessment of access routes for delivery
- Identification of utility connection points
- Discussion of any obstacles and solutions
- Preliminary advice on planning routes
- No-obligation quote based on your specific site
Conclusion
Most gardens can accommodate a granny annexe. Even gardens that seem challenging often have solutions, whether that's adjusting the position, lifting over the house, or creative groundwork. The only way to know for certain is a proper site assessment. We've installed annexes in all types of gardens, from spacious country plots to compact urban spaces. Call us on 01689 818400 to arrange your free site survey and find out what's possible for your property.
Frequently Asked Questions
What's the minimum garden size for a granny annexe?
A studio annexe needs about 70 to 80 square metres of usable garden space (including access around the building). A one-bedroom annexe needs about 90 to 110 square metres. These are surprisingly achievable in most suburban gardens.
Can an annexe be built on a sloping garden?
Yes, within reason. We can accommodate gradients up to about 1 in 10 with stepped bases or retaining solutions. Steeper slopes require more extensive groundwork and add cost. Our site survey will assess what's practical for your garden.
What if my side access is only 2 metres wide?
This is tight but often workable. We can deliver smaller sections that fit through narrower passages. In some cases, lifting over the house with a crane is possible. Difficult access adds cost but rarely makes a project impossible.
Do I need to tell my neighbours before building?
There's no legal requirement in most cases, but we strongly recommend it. Good neighbour relations make the build process smoother and avoid disputes later. A friendly conversation before works begin prevents problems.
Can I keep my existing garden shed if I build an annexe?
Usually, yes, if space allows. Sometimes relocating a shed creates a better position for the annexe. We consider all existing structures during site planning. The 50% rule includes all outbuildings, so very cluttered gardens may need some clearing.