Build a 40 Square Metre Extension Without Planning Permission
Extending your home doesn’t need to be a lengthy or complicated process. In Ireland, homeowners can increase their living space by up to 40 square metres without applying for planning permission—providing a convenient and cost-effective solution for growing families or those looking to future-proof their property.
At Garden Office Solutions, we help homeowners design and build elegant, functional extensions that transform how you use your home, all while staying within exempt development guidelines.
What Is a 40 Square Metre Extension?
A 40 square metre extension (approximately 430 sq. ft.) is a generous addition to any home, offering space for a wide range of uses—be it a modern open-plan kitchen, an additional living area, home office, or even a guest suite.
It’s also the maximum size of a rear extension you can add to a typical home in Ireland without the need to apply for planning permission, provided certain conditions are met.
Can I Build One Without Planning Permission?
In many cases, yes. According to Irish building regulations, extensions that meet the following conditions do not require planning permission:
The total floor area of the new extension does not exceed 40 square metres.
The extension is to the rear of the existing house.
There is at least 25 square metres of private open space remaining in the back garden.
The extension does not reduce the distance to any boundary below 1 metre for ground-floor windows.
The extension is not higher than the existing house.
These rules apply to houses only (not apartments or duplexes), and it’s always advised to check with your local authority or a qualified professional before building.
What Can You Use 40m² For?
A space of 40m² can significantly change the layout and function of your home. Some of the most popular uses include:
Kitchen-Diner Extensions – open-plan layouts that connect kitchen, dining, and living areas.
Multi-Use Family Rooms – a playroom by day, lounge by night.
Home Office with Storage – create a productive space separate from your main living areas.
Garden Room or Sunroom – invite natural light into your home all year round.
Granny Flat or Guest Suite – ideal for multigenerational living or occasional visitors.
Our team at Garden Office Solutions can advise on the best layout for your needs and help you make the most of every square metre.
Design and Build with Garden Office Solutions
We bring together years of expertise in home extensions, garden buildings and bespoke construction projects across Ireland. When you work with us, you benefit from:
Tailored Designs – Every extension is custom-built to match your home’s existing architecture and your lifestyle needs.
Premium Craftsmanship – Using high-quality materials, insulation and triple-glazed windows for comfort and efficiency.
Energy Conscious Builds – All our extensions are built to high thermal performance standards, often exceeding those required by Building Regulations.
Turnkey Service – From concept to completion, we manage every step so you can focus on enjoying your new space.
Advantages of a 40m² Extension
Building within the 40m² allowance provides several advantages:
No Planning Delays – Start your build sooner and reduce paperwork.
Cost Efficiency – Avoiding planning fees and potential design revisions.
Increased Property Value – A well-designed extension adds both space and market appeal.
Greater Flexibility – More space for hobbies, family life, remote work, or future needs.
Things to Consider Before Building
Before beginning your extension project, keep the following in mind:
Building Regulations – While planning may not be needed, you still must comply with building regulations.
Neighbour Relations – It’s always a good idea to let neighbours know about your plans in advance.
Drainage and Services – Ensure that any plumbing, heating, or electrics are properly planned.
Professional Support – Working with an experienced design and build company ensures a smooth process.
Start Planning Your Extension Today
A 40 square metre extension is one of the smartest ways to create extra room in your home without the stress of planning permission. Whether you’re looking to expand your kitchen, add a home office or simply make better use of your garden space, our team at Garden Office Solutions is here to help.
Contact us today to book a consultation and find out how easy it is to unlock the full potential of your home.
