As more and more people in Ireland become aware of modular housing, many homeowners are now considering modular extensions as a smart way to increase living space without the disruption of traditional construction. This increase in awareness might also be due to the government’s recent announcement that it seeks to add planning exemptions for detached modular cabins in the future.
To avoid any misunderstanding, this post is strictly about modular extensions to an existing home and not detached cabins.
So whether you’re looking to add a home office, extra bedroom, or a self-contained unit for family members, modular extensions can offer a quick, cost-effective, and sustainable alternative.
But before you proceed, there are several important factors to keep in mind. Here is a guide to help you understand the key things to consider before starting your modular home extension project in Ireland.
1. Current Planning Permission Requirements
While there are considerations to increase planning exemptions for modular stand-alone cabins in the future, current modular extensions are only exempt from planning permission if they are under or equal to 40 sq metres and located to the side or rear of the house.
Key Considerations.
- Extensions over 40 sq metres require planning permission.
- Detached structures (e.g., modular garden rooms or granny flats) need permission if over 25sqm .
- You must have 25sqm of free space left in your garden – regardless of the extension.
- If your property is in a protected structure or conservation area, additional restrictions may apply.
- You may build up to 3m high for a single pitch roof
- You may build up to 4m high for a tiled pitched roof
- Windows must not be placed within 1m of a neighbour’s boundary.
- Always apply for a Section 5 Declaration from your local authority if unsure.
2. Space and Site Suitability
Not every property may be suitable for a modular extension. Check that your site can accommodate the new structure.
Ask Yourself.
- Is there sufficient access for delivery and crane installation?
- Do you have at least 25 sq metres of private outdoor space remaining after the extension?
- Is the ground level and stable enough for a modular foundation?
These are things you might want to discuss with your preferred modular extension builder first.
3. Building & Financial Regulations Compliance
Even if planning permission is not required, your modular extension must comply with lenders and/or Irish Building Regulations. If you have a mortgage, is there a clause in your contract that prevents you from making significant modifications to your home without the bank or lender’s consent?
This might be worth checking as some conditions could void certain aspect of your mortgage contract. This is serious!
As for Building regulations, your modular extension must comply with:
- Structural safety
- Insulation and thermal efficiency
- Fire safety (especially for habitable spaces)
- Ventilation and moisture control
- Accessibility (if required)
Read more on these guidelines HERE.
4. Purpose of the Extension
Clearly define what the space will be used for.
Examples:
- Extra bedroom or living room
- Home office or studio
- Rental unit (check planning regulations for short-term lets)
- Elderly care/granny flat
Each use may have different compliance needs (e.g., plumbing, heating, access).
5. Cost vs Value
Modular extensions are generally more affordable than traditional builds, but prices can vary.
Budgeting Tips:
- Expect to pay as little as €1,000 per square meter depending on the provider or location for timber frame modular extensions. Traditional Builds might be double or more in some cases! See more on this discussion HERE.
- Get a detailed quote covering foundation work, installation, and utilities.
- Consider long-term value – will this extension improve your quality of life or increase resale value?
6. Utilities and Connections
Connecting your modular extension to existing utilities is crucial.
Points to Plan For:
- Electrical and water connections
- Sewer and waste management
- Heating (e.g., electric, underfloor, or extending existing systems)
- Internet and phone lines if needed
7. Insulation and Energy Efficiency
Make sure the modular extension meets current insulation standards.
Why it Matters:
- Better insulation means lower energy bills
- More comfortable living space year-round
- Consider applying for relevant home improvement grants or incentives for sustainable construction
8. Choosing the Right Supplier
Ireland has a growing number of modular builders, but experience and quality vary.
Do Your Research:
- Choose an NSAI-certified or reputable supplier
- Ask to view previous projects
- Read customer reviews and check after-sales service
See our list of reputable Irish modular home and extension builders HERE.
For Northern Ireland, read HERE.
9. Insurance and Financing
Confirm how your modular extension affects your existing home insurance.
Things to Check:
- Does your policy cover modular additions?
- Will your provider require structural certification?
- If financing, will your lender support modular construction?
10. Timeline and Installation Process
One of the biggest advantages of modular extensions is speed, but timelines can still vary.
Typical Process:
- Design and approval – 2 weeks
- Factory build – 2-4 weeks
- On-site installation – 1-2 days
Delays can occur due to how weather may affect delivery, and/or planning complications.
CONCLUSION
Modular home extensions can be a fantastic way to add functional, stylish space to your property in Ireland. However, careful planning is key to success. Always consult with professionals, check your local regulations, and weigh your budget and long-term goals before proceeding.
Done right, a modular extension can transform your home and add lasting value.
