One of the first questions families ask is: will an annexe fit in our garden? The good news is that granny annexes are more compact than many people imagine. A comfortable one-bedroom annexe needs a footprint smaller than most garden sheds you see in suburban gardens. Let's look at exactly how much space different annexe types require, how to measure your garden, and what affects how much space you actually need.
Annexe Sizes at a Glance
Here are typical footprints for different annexe types:
- Studio (open plan): 28 to 38 square metres (roughly 5m x 6m to 6m x 6m)
- One bedroom: 42 to 55 square metres (roughly 7m x 6m to 8m x 7m)
- Two bedroom: 55 to 75 square metres (roughly 8m x 7m to 10m x 7.5m)
- These are footprints only; you'll need additional space around the annexe
- Maximum Caravan Act dimensions: 20m x 6.8m (136 square metres)
What's Inside Each Size?
Understanding what each size accommodates helps you choose:
- Studio: Open living/sleeping area, compact kitchen, bathroom. Suits single person or couple happy with open plan
- One bedroom: Separate bedroom, living room, kitchen area, bathroom. Most popular choice for independent living
- Two bedroom: Two bedrooms, living room, kitchen, bathroom. For couples wanting guest room or carer accommodation
How to Measure Your Garden
Here's how to assess your space accurately:
- Measure the total garden area (length x width for regular shapes)
- Subtract space taken by existing structures (sheds, greenhouses, patios)
- Note any constraints: trees, slopes, buried utilities
- Identify the best position: typically rear of garden, away from boundaries
- Allow 1 to 2 metres around the annexe for access and maintenance
The 50% Rule Explained
Under permitted development, outbuildings cannot exceed 50% of your garden:
- Garden area is calculated excluding the footprint of your original house
- Includes all outbuildings: sheds, garages, extensions already built
- Your proposed annexe plus all existing structures must stay under 50%
- Example: 200 sqm garden, existing shed 10 sqm, you could add up to 90 sqm
- This rule applies to permitted development; Caravan Act may differ
What's the Minimum Usable Garden?
Based on our experience, here are practical minimums:
- For a studio annexe: 70 to 90 square metres of usable garden space
- For a one-bedroom annexe: 90 to 120 square metres
- For a two-bedroom annexe: 120 to 150 square metres
- These include space for the annexe plus access paths and outdoor areas
- Smaller gardens can sometimes work with creative positioning
Interior Space: What Feels Comfortable?
Size isn't everything; layout matters for how spaces feel:
- Good design makes smaller spaces feel generous
- High ceilings (vaulted if possible) increase sense of space
- Large windows bring the garden in, expanding visual space
- Open-plan layouts feel larger than divided rooms of same size
- Storage planning prevents clutter that makes rooms feel cramped
Bedroom Size Requirements
What size bedrooms are practical for annexe living?
- Minimum double bedroom: 10 to 11 square metres (comfortable for king-size bed)
- Comfortable double: 12 to 14 square metres (space for furniture)
- Single/guest bedroom: 7 to 9 square metres
- Consider wardrobe space: Built-in or freestanding?
- Door swing and access around bed affects usable layout
Living Area Considerations
The living space is where most waking hours are spent:
- Minimum comfortable living area: 15 to 18 square metres
- Combined kitchen-living: 20 to 25 square metres works well
- Consider furniture layout: Sofa, TV, dining area if included
- Windows and doors affect where furniture can go
- Think about daily life: Reading, TV, visitors, hobbies
Kitchen Space Requirements
Even small kitchens can be fully functional:
- Compact kitchen: 5 to 6 square metres (galley or L-shape)
- Comfortable kitchen: 7 to 10 square metres
- Essential appliances: Hob, oven, fridge-freezer, sink, washing machine
- Worktop space for food preparation is essential
- Open-plan kitchens share space with living areas efficiently
Bathroom Space
Bathrooms need careful planning in compact spaces:
- Minimum bathroom: 3 to 4 square metres (shower room)
- Comfortable bathroom: 4 to 6 square metres
- Walk-in showers are more accessible than baths and use space efficiently
- Consider future mobility needs: grab rails, shower seats
- Wetroom design maximises space and accessibility
Access and Outdoor Space
Don't forget the space around the annexe:
- Path from house to annexe (ideally level, with lighting)
- Outdoor seating area if space allows (deck, patio)
- Access for maintenance around all sides
- Space for bins, storage if needed
- Connection routes for utilities
Delivery and Installation Access
Annexe sections need to reach your garden:
- Minimum access width: 3 metres ideal, 2.5 metres possible
- Height clearance: 3.5 metres for larger sections
- Crane reach: Adjacent hard standing for crane positioning
- Road access: Space for low-loader delivery truck
- Limited access doesn't mean impossible; we have solutions
Average UK Garden Size
How does your garden compare to typical British gardens?
- Average UK garden: Around 150 square metres (varies hugely by region)
- New-build gardens: Often smaller, 50 to 100 square metres
- Older suburban houses: Typically 150 to 300 square metres
- Rural properties: Often much larger
- Even 'small' gardens can usually accommodate a studio or one-bed annexe
When Space is Tight: Creative Solutions
Limited garden? Consider these approaches:
- Compact studio designs maximise use of smaller footprints
- L-shaped layouts can fit into awkward spaces
- Positioning close to boundaries (with appropriate height) uses space efficiently
- Removing old sheds or structures frees up space
- Custom designs adapt to specific site constraints
Conclusion
Most suburban gardens can accommodate a granny annexe. A comfortable one-bedroom home needs a footprint of around 50 square metres, smaller than many people expect. Even compact gardens can often fit a well-designed studio annexe. The key is accurate measurement, understanding the constraints, and choosing a design that fits your specific space. We offer free site surveys where we assess your garden, measure the available space, check access routes, and advise on what's realistically achievable. Don't assume your garden is too small without professional assessment. Call us on 01689 818400 to arrange your free survey.
Frequently Asked Questions
Can I fit a granny annexe in a terraced house garden?
Often, yes. Many terraced house gardens are long and narrow, which can work well for annexe placement at the rear. The main challenges are usually access (side passage width) and the 50% coverage rule. A site survey will confirm what's possible.
What's the smallest annexe you can build?
A compact studio annexe can be as small as 25 to 28 square metres while still providing comfortable living with open-plan bedroom/living, kitchen area, and bathroom. Any smaller and quality of life suffers.
Does the annexe size affect running costs?
Yes, smaller annexes cost less to heat and light. However, our annexes are highly insulated, so even larger ones have modest running costs. The difference between a studio and one-bedroom is perhaps £200 to £400 annually in energy costs.
Can I extend an annexe later if I want more space?
It's technically possible but expensive and complicated. It's better to build the size you need from the start. Consider whether you might need a second bedroom in future (for carers, for example) and plan accordingly.
What if my garden is on a slope?
Sloping gardens can work with appropriate ground preparation. Gradients up to about 1 in 10 are manageable with stepped bases. Steeper slopes require more extensive (and expensive) groundwork. We assess this during the site survey.