How long does it take to build a granny annexe?

Every iHus annexe is handcrafted with care, precision and attention to detail. And while every site is different, most annexe builds follow a similar structure to ensure timescales are met and loved ones can move in a matter of weeks, not months.

Below, we break down each stage, so you know exactly what happens from day one to move in day.

How long does it take to build a granny annexe?

The on‑site construction of an iHus annexe typically takes between 8 and 12 weeks.

Smaller, one‑bedroom annexes may be completed sooner, while two-bedroom models or fully bespoke annexe designs naturally take a little more time.

Our build programme is carried out by experienced annexe specialists who follow a structured, reliable process, ensuring your project progresses smoothly from the initial groundworks right the way through to handover.

How long does planning permission take?

Before building can begin, planning permission must be secured. For most annexes, planning takes around 8–10 weeks depending on your local authority’s workload and the complexity of the application.

At iHus, we handle the full planning process on your behalf, obtaining a certificate of lawfulness (CoL) under the Caravan Act, rather than relying solely on full planning permission.

This process is generally more straightforward, less subjective, and often quicker than a full planning application – providing greater certainty from the outset. Where appropriate, we may still submit a Householder Planning Application alongside this as a secondary route, but we focus on obtaining a CoL because it offers:

• A clearer legal framework
• Reduced planning risk
• Greater certainty before construction begins
• Protection against unnecessary delays

We’re so confident in gaining CoL approval that we offer a full money back guarantee to give you complete peace of mind.

Taken together, the full journey including planning and the build typically spans 3.5 to 6 months from initial application to moving‑in day.

What’s involved in the process of building a granny annexe?

Our annexes are built with precision, care, and the finest materials, ensuring they stand the test of time. Every one of our projects reflects our commitment to excellence and your unique vision.

To make sure you receive a high-quality annexe, our process has been carefully refined to make your experience smooth from the very first conversation.

1. Initial consultation: Everything begins with a friendly conversation. We take time to understand your needs, your family situation and your ideas for the annexe. It’s also a chance to answer any early questions about layouts, planning, costs or feasibility.
2. Quotes and drawings: After the consultation, we’ll share a detailed proposal that includes:
   • A clear breakdown of costs
   • A payment schedule
   • Scaled drawings showing the annexe layout
   • Information about planning routes
   • Any early considerations for site preparation
   • Expected timelines for planning and build
   • Details of our insurance‑backed 10‑year guarantee

   You’ll have the opportunity to review everything and ask questions.

3. Site survey: Once you’re ready to move forward, we book a comprehensive on‑site survey. One of our consultants will visit your garden to assess:
   • Access
   • Terrain
   • Drainage
   • Utilities
   • Annexe positioning
   • Any constraints or limitations on site

   This ensures the final specification is accurate and your build runs smoothly.

4. Finalise your specification: This is where your annexe becomes personal. Working with your iHus consultant, you choose:
   • Kitchen colours, styles and appliances
   • Flooring and internal doors
   • Lighting and electrical finishes
   • Bathroom options
   • Exterior cladding and roof finishes
   • Any accessibility features
   • Additional upgrades or bespoke touches

   It’s a collaborative process between you and our team that ensures your annexe reflects your needs and your style.

5. Planning permission: Supported by annexe planning experts, we prepare and submit your application, ensuring the entire planning process is stress-free and taken care of on your behalf. We manage:
   • All drawings
   • Supporting documents
   •  Application forms
   • Any amendments requested by the council

   You’ll be updated throughout, but we handle all the leg work so you don’t have to.

6. Annexe build: Once we have obtained permission, then the construction can begin. From the moment our build team sets foot on site, they will ensure the following elements are completed to the highest standard:
   • Groundworks: foundations, drainage and service connections
   • Structural build: walls, roof, windows and doors
   • Internal installation: plastering, electrics, plumbing, kitchen, bathroom
   • Finishing: flooring, decoration, trims, fixtures
   • External features: decking, steps, pathways or lighting (if chosen)

   Our builders work respectfully and efficiently, minimising disruption while maintaining the quality annexe build standards your new home deserves.

7. Handover and aftercare: With the finishing touches complete, we walk you through your new annexe, showing you where everything is and how it works. You’ll also receive:
   • Your keys
   • Your guarantee documentation
   • A chance to identify anything you’d like us to perfect during our snagging process

   Six months in, a member of our aftercare team will be in touch to arrange a visit and see how you’re getting on with your annexe. You’ll also have the option to join our OpenHus community and allow others the chance to start their annexe journey.

Why choose iHus to build your granny annexe?

As the UK’s only specialist annexe provider, we bring unparalleled experience and expertise to every project. With over 500 annexes completed, we understand and support every question, sensitivity, and scenario you might face.

Our unique OpenHus network features over 120 real annexe owners ready to welcome you for a visit. You can also discover what annexe living is really like by visiting our Be Inspired page, which gives you a closer look at how our annexes are positively impacting lives across the UK.

How long does it take to build a granny annexe – At a glance

From the initial quote being approved to move-in day, most iHus annexes are completed within 3.5 to 6 months.

This timeframe typically includes:

• 8-10 weeks to secure planning permission or a Certificate of Lawfulness
• 8-12 weeks for on-site construction, depending on size and specification

Because our entire process is carefully managed, there’s no unnecessary waiting in between stages. Once approval is in place, your build is scheduled and constructed with precision.

Every garden layout and annexe design is unique, so exact timelines can vary slightly. But with a clear process, specialist planning support, and experienced in-house build teams, we can make the annexe dream a reality.

If you’d like a personalised timeline for your garden and layout, our team will be happy to walk you through it.

Ready to bring your annexe to life?

If you’d like to explore your timeline, your options or the possibilities for your garden, our team is here to help.

Request a free brochure, book a consultation, or speak directly with our experts today.

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