Not always. Many single-storey rear or side extensions can be built under Permitted Development (PD) rights, bypassing the need for full planning permission. To qualify, the extension must adhere to strict height and volume limits, and must not extend past a certain distance from your original house wall. However, if your property is a flat, has been extended extensively in the past, or is located within a Cardiff conservation area - such as parts of Pontcanna, Whitchurch, or Penylan - planning permission is usually required. We always assess your property's specific boundaries and check local council records during our initial site survey.

We can provide a complete turnkey service, which means we can handle the entire project from end to end. This includes creating the initial architectural design and 3D mock-ups, producing detailed structural engineering calculations, and managing all council submissions on your behalf. However, if you already have an architect and possess a set of approved drawings, we are equally happy to act purely as the main contractor. We will review your existing plans, provide a comprehensive build estimate, and execute the construction flawlessly.

On average, a standard single-storey rear extension takes between 8 to 12 weeks on-site, while a larger two-storey extension can take anywhere from 12 to 16 weeks. The exact timeline depends entirely on the scale of the build, the complexity of the foundations, the ground conditions, and the weather. If your project includes structural wall knock-throughs to create a wide open-plan kitchen, or requires complex roof alterations, it will sit toward the upper end of those estimates. We keep a tight rein on our building schedules to ensure trades move seamlessly from one phase to the next.

Yes, adding high-quality square footage to a property is widely regarded as one of the most reliable ways to increase its market value. Data across Cardiff and South Wales indicates that a professional, building-regulation-compliant extension can increase a home’s total market value by as much as 15% to 25%, depending on the size and location. Adding an extra bedroom, a multi-functional family space, or a large open-plan kitchen-diner offers an exceptionally strong return on investment, making your home far more appealing to future buyers.

We build all varieties of residential extensions, customising the design to fit your property layout and goals. The most popular options include single-storey rear extensions (perfect for open-plan kitchens), side-return extensions (ideal for maximising narrow pathways on terraced or semi-detached homes), and wrap-around extensions that combine both. We also specialise in two-storey extensions to add extra bedrooms and bathrooms upstairs, as well as over-garage extensions that build upon existing ground-floor footprints.

In the vast majority of cases, no, you can remain living comfortably in your home. For the first few weeks of the build - during the excavation, foundation pouring, bricklaying, and roof installation - our team works entirely outside your existing house. Your home stays sealed off, weather-tight, and secure. The only time we truly need to breach your living space is during the final stages when we knock through the original external wall to link the old house to the new extension, a phase we manage quickly, cleanly, and with dust screening in place. To learn more, check our guide on what to expect during a building project.

Yes, securing building regulations sign-off is a mandatory legal requirement for all extensions, and we manage the entire process for you. We submit the necessary building notices to Local Authority Building Control or a registered private inspector. Our team coordinates directly with structural engineers to ensure the foundations, steel lintels (RSJs), insulation, and drainage meet all current UK building standards. We manage every inspection throughout the build, leaving you with full compliance paperwork at the end.

Standard strip foundations for a domestic extension typically need to be a minimum of 1 metre deep. However, the exact depth depends entirely on the soil conditions of your specific area in Cardiff and whether there are any large trees or public sewers nearby. For instance, clay soils or nearby mature trees may require deeper foundations or a specialist raft/piled foundation to prevent future movement. We handle all ground testing and coordinate with building control inspectors during the excavation phase to ensure your foundations are perfectly solid.

Yes, it is very common to build near or over a public sewer, but it requires a Build Over Agreement from your local water authority - which in Cardiff and South Wales is Welsh Water (Dŵr Cymru). If a public sewer run is located within 3 metres of your proposed extension's foundations, we must submit detailed plans showing how we will protect the pipes. This often involves bridging the sewer with structural concrete beams or encasing the pipes to prevent damage. We guide you through this application process before any ground is broken.

We believe a great extension should look like a natural evolution of your home, not an awkward bolt-on. We take immense care to source building materials that closely match your existing property. This includes tracking down matching brick types, mortar colours, roof tiles, and rendering finishes. We also pay close attention to internal details, replicating architectural elements like your original skirting boards, door frames, and plaster coving to ensure a completely seamless transition between the old and new spaces.

If your home is a terraced or semi-detached house and your new extension involves digging foundations within 3 metres of a neighbour’s structure, or inserting steel beams into a shared wall, it will likely trigger the Party Wall Act 1996. This requires you to serve your neighbours with a formal written notice at least two months before construction begins. While the legal responsibility rests with you as the homeowner, we can provide guidance, help prepare the paperwork, and connect you with certified party wall surveyors to ensure everything is handled smoothly and legally.

The choice comes down to budget, design, and planning rules. Flat roofs - which can be constructed using modern, highly durable materials like EPDM rubber or GRP fibreglass - are generally more cost-effective, can accommodate large skylights, and are ideal if you want to minimise the impact on your upstairs windows. Pitched roofs are traditionally more expensive because they require complex timber roof trusses and tiling, but they offer classic architectural appeal, vaulted internal ceilings with Velux windows, and an exceptionally long lifespan.

RGB Construction is a fully verified, registered member of the Federation of Master Builders (FMB). This membership guarantees that our workmanship, on-site safety practices, and company finances have been rigorously inspected and vetted against strict industry standards. We are fully insured with comprehensive public and employers' liability insurance, meaning your large-scale home extension project is entirely safe in the hands of a recognised, professional Welsh building firm.

Yes, absolutely. We stand firmly behind the structural integrity and quality of our construction work, which is why every home extension we build comes backed by our comprehensive company guarantee. We only use premium building materials and proven trade professionals. Once your extension passes its final local authority inspection and we hand over your keys, we provide an organised completion file containing your official Building Control certificates and our formal warranty documentation.

Getting started is completely straightforward and carries zero obligation. Simply reach out to us by phone or fill out the quick contact form on our website. We will set up a convenient time to visit your property for an on-site consultation. During our visit, we’ll assess your garden space, review any drainage layouts, discuss your design ideas, and explain potential planning constraints. Following the site assessment, we will provide a fully itemised, transparent, and fixed-price quote for your review.