What would it cost to re-do an old, small, extension?

A homeowner seeking to rebuild an old, small extension faces a complex set of considerations, according to quantity surveyor Shay Lally of Houses to Restore. The estimated cost for such a project ranges significantly depending on the scope of work, materials chosen, and whether structural modifications are needed. The extension in question measures approximately 20 square metres, a size typical of many smaller additions constructed decades ago. Before proceeding with a complete rebuild, Lally advises assessing the current condition of the structure. Some older extensions may still be structurally sound, requiring only updates such as a new roof, improved insulation, and modernisation of fixtures. These repairs could save considerable money compared to a full-scale reconstruction. However, if the extension is severely deteriorated, often due to outdated construction methods or lack of maintenance, a complete rebuild may be more practical. The process begins with the demolition and removal of the existing structure. This phase includes several preparatory steps essential for safety and compliance. A plumber must be present to isolate the heating and plumbing systems, particularly if the extension contains a gas boiler. A registered gas installer is required to safely disable the gas supply and remove the boiler. Similarly, an electrician must disconnect the circuits associated with lighting and power points within the main house. These precautions are crucial to prevent hazards during the demolition phase. Temporary works are another critical component of the project. After the extension is removed, the remaining house must remain secure and protected until the new structure is completed. Temporary supports, scaffolding, and protective coverings are typically installed to ensure the integrity of the existing property during construction. Once the site is cleared, attention turns to the new extension itself. The cost per square metre for constructing the new addition varies widely based on design choices and material specifications. A basic extension featuring sand and cement render, torch-on roofing, and uPVC windows can cost between €3,500 and €5,500 per square metre. In contrast, a more elaborate design incorporating brickwork finishes, aluclad windows, and a zinc roof may exceed these figures substantially. Internal finishes also play a role in determining final costs. Choosing standard options such as laminate flooring, standard electrical fittings, and conventional paints keeps expenses manageable. Conversely, opting for higher-end features like engineered wood flooring, premium paint brands, and advanced electrical components increases the overall budget. Connecting the new extension to the main house introduces further considerations. Structural alterations often involve modifying the back wall of the existing home. Temporary supports are installed before sections of the wall are cut away, allowing for the insertion of steel beams and columns. This step ensures the structural stability of both the new extension and the original house. Lally notes that while some existing openings may already align with the new design, many older extensions are poorly integrated into the main structure. Rebuilding offers an opportunity to improve the architectural flow between the two spaces, emphasizing the importance of thoughtful planning and design in the process.