At O'Callaghan Construction, we help homeowners across Cork unlock the full potential of their homes with high-quality, professionally built extensions. Whether you're looking to create more living space, add a home office, expand your kitchen, or build upwards with a second storey, we provide expert advice and skilled craftsmanship from start to finish.
Extending your home is often a more practical and cost-effective solution than moving, especially if you love your location but need more room. We work with your existing structure to create seamless, functional, and beautiful additions that suit your lifestyle — and your budget.
This is one of the most frequent questions we get asked, and understandably so. The cost of building an extension can vary widely depending on factors like the size of the extension, the level of finish you choose, and whether you're upgrading any existing systems as part of the work.
Some homeowners add a simple single-storey extension to the rear of the house, while others include upgrades such as replacing windows, improving insulation, or modernising the heating system. These extra layers make pricing a bit of a “how long is a piece of string” scenario, which is why we always work with a quantity surveyor (QS) to provide realistic, high-level estimates.
Typically, we provide costings based on drawings, broken down into cost per square metre, with flexibility for different materials and finishes. We'll often provide a guideline range - for example, plus or minus 10 to 15% - depending on the specification. This helps you understand your budget from the beginning while allowing room for personalisation.
Planning your new house extension in Cork? Get in touch with us for expert building advice and costings!
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Build times depend on the size and complexity of the project. A typical single-storey extension might take around four to six months, while a larger or two-storey extension could take up to seven months. We always aim to provide a realistic timeline from the outset and work efficiently to minimise disruption.
We also understand that most extensions are built while you're living in the home. Our team is experienced in working in and around occupied properties. We take care to maintain a clean and safe site, keep noise and disruption to a minimum, and communicate clearly so you always know what to expect next.
We work on a wide range of residential extensions, including:
Each project is unique, and we tailor our approach to fit your vision, your home, and your budget.
We offer a full construction service, managing all trades and project coordination so you don't have to. This includes everything from groundworks and structure, to electrical and plumbing, to the final finishes. We can also work with you on Prime Cost (PC) sums - providing allowances for kitchens, tiling, bathrooms, etc., so you can personalise key elements of the build without unexpected costs.
Once construction is complete, we carry out a thorough review with you and your engineer or architect to ensure everything meets the agreed standard. If any minor issues arise, they're added to a snag list and resolved before the final payment stage.
In many cases, yes — especially for larger or two-storey extensions. However, small extensions may fall under exempted development, meaning you won't need full planning permission. An architect or engineer can help assess your specific situation and determine what's required based on local regulations and the scale of your project.
If you're not sure, we're happy to recommend a local architect or engineer to help you get started. We often work with clients once they have their drawings and planning approved, but we're also available for advice earlier in the process if needed.