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6 Key Steps to Buying a Granny Annexe in 2023

Where to start when buying a granny annexe?  Firstly, the term granny annexe is somewhat outdated. Annexes are for multi-generational living for both young and old, specifically for family members.

It is challenging when the need arises to provide independent living and support for you or a loved one.

There are many questions to consider;

  • Should I build a log cabin or a garden room?
  • Shall I extend?
  • Why should I choose an annexe?
  • Is a brick-built annexe vs timber frame more cost-effective?
  • Can I use the existing foundations of a garage/outbuilding?
  • What size annexe will work in the space available?
  • Do I need to appoint an architect or planning consultant?
  • What are the upfront costs?
  • Who do I get to connect the utilities, undertake ground works and build the annexe?
  • Which foundation is best when close to trees?
  • Do I need an arboricultural report?
  • How long does planning take?
  • How would I benefit from an Asset Plan?
  • What are the chances of getting planning approval?
  • How will living in a Green Belt / Conservation area affect my planning application?
  • Will the annexe be UK Build Regulation Certified?
  • How can I increase my chances of acquiring planning approval for a Listed property?
  • How can I improve the success of obtaining planning permission?
  • How long will it take until I can move in?
  • What does it cost?
  • Do I pay VAT? 
  • Is the project fully managed?

iHus is recognised as the leading Granny Annexe company in the UK, providing guidance and support on multigenerational living and all topics surrounding this way of living.

When personal circumstances change due to the loss of a loved one, declining health, or simply the need to downsize and be closer to loved ones, finding a house with a granny annexe isn’t an easy task. With a significant increase in the demand for annexes the perfect solution for many is a purpose-built garden annexe.

There are three main scenarios where people consider adding an annexe to their garden; each comes with its own challenges and specific needs.

3 Main Scenarios When Buying a Garden Annexe

  1. Building an annexe in your garden to move a family member in.
  2. You’re selling up to move into an annexe in your family member’s garden.
  3. You and a family member plan to sell two houses and buy a house to add an annexe to.

Whether you are considering moving to a new property or having the annexe built at an existing property, the essential step is to determine if planning approval for the annexe is viable.  It is at this point that we provide our clients with a free Preliminary Planning Report within 48 hours—a comprehensive insight to make an informed decision on how best to proceed, even before you decide to place an offer on a property.

An annexe in the garden of is owner

6 Key Steps to Buying an Annexe in 2023

  1. Garden Annexe vs Garden Rooms and Log Cabins – Only a build-certified annexe will do!

General garden rooms are ideal for games rooms, office space, gyms, and generally multi-functional spaces, but they are not deemed suitable or compliant as habitable spaces.  Home Lodge / Log cabins can be habitable but are not compliant with part L of the building code, lacking the necessary insulation values for a certified building built to UK building regulations.  Annexes can be brick-built or timber framed attached to the house or located in the curtilage of a property.  An annexe building is ancillary to the main dwelling and explicitly built for a family member.  iHus is the only UK annexe provider to build bespoke certified annexes to meet UK and NHS regulations with ISO9001 quality management mark.

2. Annexe Planning Considerations – Save on architect costs

Avoid unnecessary costs of an architect / and or a planning consultant.  An experienced architect has broad knowledge in all areas of a building, but may not be a specialist when designing an annexe.  Appointing an architect will incur a direct cost and will likely incur additional fees for changes to your design and planning application.  Quickly finding out the viability of building an annexe without incurring costs is crucial before committing to a project.  An annexe can be attached to the main dwelling.  However, this comes with additional costs for architects’ fees and a hefty 20% VAT added to the total project price.  Choosing a standalone annexe avoids these costs.

As specialists in the design and build of bespoke annexes, iHus in-house planning division NAPC consults Local Government on annexe planning applications.  Our experience, knowledge and approach to securing planning approval are second to none, with a planning approval rate of over 96%.  We undertake a dual planning application that includes Full Planning and planning under the Certificate Of Lawfulness (COL), also known as The Caravan Act.  To ensure the correct build methods are used in constructing your annexe building, you should check that it is being built and classified as a Certified Building, built to UK Build Regulations and compliant with NHS regulations.  A certified build also benefits from cheaper insurance premiums.

To determine the viability of adding an annexe to a property, our free Preliminary Planning Report will deliver essential planning information about the local authority, water authority, areas for concern/consideration and proposed approach to planning.  Results help for quick decisions with report findings available within 48 hours; the report is ideal when considering the purchase of a property or establishing the suitability of an annexe, style, size and location in the garden before you commit to any cost.

Granny annexe with flower beds in its owners back garden.

3. Annexe Building Location is Key – Avoid major pitfalls

An annexe must be located within the curtilage of the main dwelling.  The curtilage is deemed the front, drive, side and rear garden and must not exceed 50% of the curtilage.  Building an annexe on land that you own as part of your estate but is specified as woodland, paddock or agricultural land is not permitted for an annexe.  Building an annexe on land outside your curtilage will require planning permission for land change of use and an independent dwelling.

When considering a granny annexe in the garden, be mindful that your council will review the “street scene” and the impact of the annexe on the road and neighboring properties.  Councils discourage locating an annexe in the front and side gardens, preferring an annexe nearer the house to support an ancillary argument.  That said, iHus have often designed and built an annexe at the bottom and side of the garden, so all projects are reviewed on a case-by-case basis.

Water Authorities have the same power as your local authority and the right to take a building down.  Managing the build process is vital when reviewing build-overs for existing pipework.  We assess build-over risk factors for each project and constantly evaluate information to mitigate risk.

When an annexe is located at the bottom of a slope that rises to the main dwelling and drainage point, the cost of a pressurised pump will need factoring in.  The first 10 meters of drainage, water and electricity are included as standard with iHus and charged per meter afterwards.

An annexe is connected to a bio tank for non-main drainage, which will require specific distances from habitable dwellings, boundaries, and water courses.  The legislation stipulates an annexe cannot be connected to an old septic tank unless it has recently been replaced compliant with current legislation and has sufficient capacity.

If you wish to locate an annexe close to mature trees, first identify if the trees are listed under a Tree Preservation Order (TPO).  Your council will require special permission if the building impacts the surrounding trees.  An annexe can be built close to a tree, subject to age, size and TPO status.  In these instances, ground screws are the favoured foundation, allowing screws to be moved, avoiding tree roots whilst maintaining build integrity.  Your council may require an Arboriculture Report to review the impact of the build on the surrounding trees.

Where windows back onto a boundary, the required distance to the boundary will be 750mm minimum.  An annexe may be located closer to the boundary, subject to adherence to specific building regulations.  Consideration must allow for the space needed to construct the building.

A granny annexe home in its owners back garden

4. The Right Foundation for an Annexe Property – Minimal disruption and cost

An annexe will be raised off the ground at least 40cm or two-step height, with an insect mesh around the skirting to keep out any unwanted guests.  Depending on soil conditions, there are several foundations typically used:

  1. Ground Screws – A metal corkscrew starting at c1.2m in length is screwed into the ground at set points.  
  2. Concrete Pads – are large cylindrical shape concrete piled into the ground.

Each option ensures minimal disruption to the garden area, and is preferred by both planning offices and arboriculturist, for their eco-friendly approach, unlike conventional concrete slabs that require major excavation and groundwork.

When removing an existing building, be mindful that an old concrete base may not be a sound starting point to build your garden annexe.  Seek expert advice on the suitability of the existing foundation to avoid significant cost implications further down the line.  If we are looking after your annexe project however, we will do this for you.

Locating an annexe on level ground is not always possible and may require additional ground works to scrape the area level or need more substantial groundwork involving retainer walls.

5. Identifying The Best Annexe Design For You  – Bespoke designs that future-proof your needs

It is never easy to downsize… deciding what to keep,  or making a fresh start with everything new.

Accepting that the size of the annexe is often governed by space available is a good first step.  iHus always build annexes with future-proofing in mind, so consider floor plans if a one-bedroom is suitable, or if there will come a time when live-in help is required, and two bedrooms are needed.  Perhaps you want to hold onto cherished pieces of furniture, in which case, wall space may be a critical factor in your garden annexe design.  Annexes range in size from one bedroom up to large two bedrooms.  However, the second bedroom can easily be used for a hobby room, study, or office area, creating a spacious one-bedroom home with flexible living.

The prime considerations for a living space are open plan or enclosed areas, such as the kitchen, a separate bathroom for guests, or an ensuite.  With more extensive annexes, there are options to have a utility, guest bathroom and ensuite.  Depending on planning requirements and location, a flat roof might be preferable over a pitched roof with a vaulted ceiling and additional loft storage space. 

For a Listed Property in Green Belt, Areas Of Outstanding Natural Beauty, or Conservation Areas, the design and aesthetic of the building are critical, with councils leaning toward the more traditional build of pitched roofs with tiles and possibly oak cladding to blend with the surrounds.

Window location is important concerning the sun’s trajectory, so consider where the sun rises and sets in the garden, with a well-located decking area for morning coffee or an evening relaxing as the sun goes down.  When designing your annexe, consideration should be given to the total glazed area to ensure that the building is compliant with the Government’s “Part L” Insulation and Ventilation Rules to ensure your build U values are maintained.

A scenic back garden with the sunshine and a customers annexe home

6. Choosing the Right Company – Multiple trades or a one-stop solution

There are critical factors to consider when choosing a provider to build and plan out your annexe. Consider the size and experience of the company based on building annexes.  Will the company manage the whole project or expect you to find other parties?  If they are introducing other parties, who is responsible for the building, or do they provide a turnkey solution with full responsibility?

iHus Stages of Buying an Annexe

At the start of your annexe buying journey, we know how important it is to have all the facts,

so here are the key stages in the buying process of an iHus annexe, to help you make an informed decision with a full turnkey solution provider.

  1. Preliminary Planning Report – free and ready in 48 hours, identify the viability of securing planning approval.
  2. Virtual Consultation  – identifies the best annexe design, location, size and finish ready for quoting.
  3. Show Home – visit a show home (a lived in annexe), to get a real sense of annexe life – speak with the annexe owners, ask any questions you may have, and help decide if an annexe is for you.
  4. Quotation – a free in depth itemised quotation includes elevation drawings, layout plans, electrical plans and computer generated images (CGIs) of both internal and external views.
  5. Site Visit – on your decision to proceed, we will undertake a site visit and take a deposit of £4,200 (fully refundable if we are unsuccessful in planning).  The site visit generally takes 4-6 hours; we stake out the annexe, taking measurements and showing product samples.
  6. Raise the Contract – for sign-off of the project.
  7. Keys Hand Over – from the date of our site visit, we expect to hand over keys within six months, ready to move.

For further reading on our buying stages, please see our Signature Move page.

iHus customers stood talking to granny annexe home owners in their house.

For many of our customers, they love how we take care of everything throughout the annexe buying / building journey. So for all those questions which may be flying round your head (as set out at the start of this blog), we hope this blog has answered quite a few of them – but really if you go ahead with iHus as your annexe provider and builder, you need not worry about sourcing all the answers anyhow – as we take care of it all anyway.

To find out more about any of the steps outlined above, or to take the leap and start discussing your annexe journey with us, be sure to get in touch!

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Download our iHus annexe brochure

Download our iHus annexe brochure

If you would like to download our annexe brochure, please complete the form below. You can also request for a hard copy to be posted to your home address. Have any further questions, why not request one of our team get in touch?

If you would like to download our annexe brochure, please complete the form below. You can also request for a hard copy to be posted to your home address. Have any further questions, why not request one of our team get in touch?


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