How to create a granny annexe that works for everyone

A granny annexe is self-contained accommodation within or attached to your main home, usually with its own bedroom, bathroom and kitchen.

You might also hear it called a granny flat, granny pod or garden annexe, but it is different to a garden room which is usually an extra space for working, exercising or relaxing rather than somewhere designed for independent living.

A granny annexe normally needs to remain ancillary to the main home rather than becoming a separate dwelling. And when it’s done well, it can give a family member somewhere that feels entirely their own whilst keeping you nearby.

There are lots of reasons that several generations might live under one roof – or at one address. For some families, a granny annexe means an ageing parent can stay close to the people they love while keeping their independence. For others, it gives grown up children somewhere affordable to live while they save for a home of their own. And sometimes, families simply want to spend more time together without actually sharing a kitchen every morning. 

Some of the benefits of multi-generational living include: 

• More independence: everyone gets their own space, routines and privacy. 
• Family is nearby: company, help or childcare can be just a few steps away when you need it. 
• Less upheaval: an older relative might be able to move closer without the family needing to move house. 
• Flexibility: a granny annexe can adapt as a family's needs change over time. 
• Shared costs: living closer together can make some household expenses easier to manage. 

The trick is getting the balance right. A good granny annexe should make it easy to spend time together and close the door when everyone needs a bit of space. 

No – as long as your project meets the conditions set out in the latest planning exemptions published by the Irish government in July 2026. 

These conditions include: 

• 32m² to 45m² floor area  
• Rear garden only 
• One storey only 
• Connected to the main house’s water, electricity and drainage 
• Maximum 4-metres height  
• Building regulations compliant 
• Registered with local authority 

This is great news for homeowners who want to create a granny annexe quickly and without the hassle of going through planning. But be aware that the exemption is temporary – works must take place by (and the exemptions expires on) 31 December 2030. 

Unsure if your plans meet all of the criteria? Speak to your local planning authority for advice. 

It’s a good question – and you’ll be pleased to know that there’s plenty of room from the smaller 32m² to the more generous 45m².

As a guide, you could expect:

It all depends on what you need from your granny annexe and the budget you have to play with, along with local costs for building, materials and everything else you need to get the granny annexe fully functioning. 

A granny annexe should work for whoever is living there right now, but it's worth thinking about what they might need in the future, too. A few thoughtful design choices at the start could save you from making bigger changes later. 

If you're creating a granny annexe for an older relative who has accessibility needs, you could think about: 

• Step-free access at the entrance and between rooms 
• Wider doorways with plenty of room to move around 
• A walk-in shower rather than a bath or raised shower tray 
• Grab rails in helpful places such as the bathroom 
• Easy-to-reach storage, sockets and switches 
• Enough space to move around comfortably if their needs change 

Comfort matters just as much. Try thinking about heating, ventilation and daylight early on, rather than treating them as finishing touches. For example, if you have limited wall space in your structure, a roof window could help you draw in light from above and make the space feel brighter and roomier.

The place you build your granny annexe in depends on the space you have, your budget and how you want it to function. 

Popular choices include: 

• In the garden: a separate annexe can offer the most privacy while keeping family a short walk away. 
• As a side or rear extension: attaching the annexe to your home makes it easier to move between the two spaces. 
• In a converted garage: if you already have a usable structure, a garage conversion into a granny annexe could be a great use of space. 
• Within your existing home: reworking part of your home can create a separate living space without having to build from scratch. 

It's all about finding that sweet spot: close enough to be there when you're needed, with enough separation for everyone to still feel independent. 

There’s no one-size-fits-all answer when it comes to the cost of a granny annexe. Irish extension benchmarks are around €2,000–€3,500+ per square metre – and you could spend anywhere from €40,000 for prefabs to €250,000 for larger brick-and-mortar structures. 

But don’t let these numbers put you off. Straightforward conversions could cost much less, so it’s always worth getting a building quote – or a few – to get a feel for rates. 

Published prices can vary depending on what's included, but here’s a rough estimate:

Before setting your budget, check whether your quote includes things like planning and professional fees, foundations, drainage, electricity and water connections, kitchen and bathroom fittings, and landscaping. You might also want to leave some money aside for anything unexpected.

Creating a granny annexe and knowing your loved ones will be closer can be very exciting, but there are also a few tax and legal details worth understanding, especially if you're building for a relative or thinking about what might happen to the space in the future.

A self-contained granny annexe or modular garden home might have a separate Local Property Tax (LPT) liability if it’s capable of being used as an independent dwelling. However, if it’s a part of the main building and owned by the same person, you might be able to value it together with your main property. Ask your local planning authority for advice if you’re unsure.

Irish stamp duty is mostly applied as a tax on the purchase or transfer of property, rather than on improvements you make to a home – so your new granny annexe shouldn’t be affected. But we always recommend checking with your planning or building professional, or your local authority.

If the annexe was approved as ancillary accommodation to your main home, they are generally treated as one property rather than two separate homes. But if you want to sell or rent the annexe out as a separate dwelling later on, you might need to apply for planning permission or have existing planning conditions changed. Your local authority can tell you what applies to your property.

There’s a lot to think about when building a granny annexe, so it’s easy for things to get missed. A little planning early on can save you time and money and help you create a space that’s adaptable with your family for years to come. 

Here are some of the most common mistakes to avoid: 

• Assuming you won’t need planning permission: permitted development doesn’t automatically apply to every granny annexe, so check before making any firm plans. 
• Designing first and checking the rules later: find out what’s possible for your property before making a call on a particular size, position or layout. 
• Budgeting for the build alone: consider professional fees, groundwork, utility connections, fittings and a little more for unexpected costs. 
• Only thinking about what works today: step-free access, wider doorways and an easy-to-use bathroom might not feel essential now, but could make a big difference later – especially for any ageing family members. 
• Leaving daylight and ventilation until the end: think about where light and fresh air will come from while you're planning the layout – that’s much easier than trying to squeeze in extra windows once everything else is decided. Our roof window size guide can help you find an option for your granny annexe that you (and your family) will love. 

If a granny annexe feels like the right option for your family, try using this quick checklist to kick off your project: 

• Work out what you want the space to do: who will live there? How much independence do they need? And what would make everyday life and accessibility easier for them, such as step-free access?
• Speak to a professional: find a planner or builder who specialises in granny annexes. They can look at your property, work out what’s possible and help you understand the planning route before you go into the finer details. 
• Think about light: daylight can have such a huge impact on everyday life. If there’s a room your loved one will spend a lot of time in, could you maximise the light coming in with a VELUX roof window or flat roof window, and protect the space from getting too hot in the summer with anti-heat blinds. Making a call on this upfront will help you create a space that’s bright, fresh and comfortable to live in. 
• Set your timeline: granny annexes can take several months to move from initial ideas through planning, design and construction, and more complicated projects could take longer. Decide on a timeline or set a goal, and you can start working towards it. 

Want to dig into some inspiration first? Discover how light and ventilation can transform your home, from climate control in smaller structures to creating sun-drenched family spaces.