Building the Perfect Annexe: Design, Planning & Cost

Creating a granny annexe is a fantastic way to provide independent living space for a loved one or enhance your home’s functionality. More young adults are staying at home longer than ever in 2025 (13% of people in the UK aged between 25 and 34 in 2006, compared to 18% in 2024 according to the IFS, Institute for Fiscal Studies). Furthermore, granny annexes are also a popular option in the UK for accommodating elderly relatives who may require domiciliary care as the population ages.

iHus is a specialist granny annexe provider who has been helping families in the UK for the past 20 years, providing individuals the freedom of independent living whilst having access to help and support from family members. From the initial annexe design to obtaining annexe planning permission, and understanding costs associated (including council tax), here’s everything you need to know about building the perfect annexe.

Designing Your Dream Annexe

Designing your annexe is an exciting part of the journey. Whether it’s a comfortable space for a family member or a multifunctional addition to your home, your design should meet its intended purpose while complementing your property.

Key design tips:

  1. Maximise Space: Clever layouts and storage solutions can make even compact spaces feel open and functional.
  2. Ensure Accessibility: Features like wide doorways, step-free access, and adaptable fittings are particularly valuable for elderly or disabled occupants.
  3. Create Cohesion: Use materials and finishes that align with the main property for a harmonious look.

When it comes to getting the design right, partnering with an annexe specialist like iHus ensures your design is practical, stylish and optimised for everyday living.

Planning Permission Made Easy

Planning permission for granny annexe applications can feel daunting, but with iHus, it’s hassle-free. Our expert team takes care of the entire process, from initial applications to securing final approvals.

Do you need planning permission for an annexe?

Yes, in most cases, planning permission is required. At iHus, we take two tailored approaches depending on the annexe range:

  • Classic Range: We manage the full planning process with your Local Planning Authority (LPA), leveraging our 94% success rate to secure approvals.
  • 3632 Range: Planning permission is not needed as this model falls under the Caravan Act, also known as a Certificate of Lawfulness (COL), offering a simpler alternative.

Your Peace of Mind Guaranteed

If planning permission is not granted for an annexe, we offer a full money-back guarantee, refunding every penny you’ve spent with us so far. With experience working with over 250 LPAs, you can trust us to get it right.

Understanding the Cost of a Granny Annexe

The cost of a granny annexe with iHus starts from £95,750, covering high-quality builds tailored to your needs. Additional costs may apply depending on size, design preferences, and materials. Beyond the construction phase, remember to account for ongoing expenses like maintenance, utilities, and council tax.

Council Tax for Granny Annexes

Annexes must be separately banded for council tax, but recent changes have made them more affordable. Here’s what you need to know:

  • 50% Discount: Available if the annexe is occupied by a family member or used as part of the main property.
  • Exemptions: If a dependent relative (aged 65+, disabled, or severely mentally impaired) resides in the annexe as their main home, it may be entirely exempt from council tax.

To confirm eligibility for discounts or exemptions, contact your local council with details about your annexe and its use.

Why Choose iHus?

At iHus, we specialise in creating high-quality, eco-friendly granny annexes that perfectly balance style and practicality. From bespoke designs to seamless planning permission and expert construction, we handle every step of the process. With a 94% planning success rate and extensive knowledge of council tax rules, you’re in safe hands.

With a choice of over 12 annexe designs, and various material and size to choose from, iHus has the perfect garden annexe for you. To view our self-contained garden annexes for yourself, you can either visit one of our OpenHus show homes in person, or browse through our online catalogue.