Home Extensions

Many homeowners choose to extend their property primarily due to the need for more space. Whether it's developing a larger kitchen and dining area with a rear extension, adding a side extension for a study or annex, or creating a two-storey addition to increase bedroom capacity, residential extensions can significantly enhance how the space functions for your family. CADGUYS specializes in helping homeowners formulate a planning strategy to turn these ideas into well-designed and buildable projects.

Every extension project begins with understanding how you currently use your home and what changes could improve it. At CADGUYS, we work with homeowners to explore the daily functions of the household, considering factors such as privacy, how spaces connect, and areas of the existing property that may be missing or underperforming. This comprehensive analysis aids us in identifying where additional space would be most beneficial, whether that means extending to the rear, the side, or developing space above the existing building. 

An important early consideration is the budget for residential extensions. Current construction costs typically range between £2,500 and £3,000 per square metre, so having a clear understanding of the likely budget helps guide the planning strategy and ensures the proposed extension is realistic and buildable. Once we understand the required space and how it aligns with the available budget, we can begin developing a design strategy and move into the planning stage.

Once we understand the type of space you wish to create, CADGUYS will advise on the most appropriate planning strategy to bring your vision to life. For many residential extensions, there are significant opportunities through permitted development rights, which allow certain types of extensions to be constructed without the need for a full planning application. Typically, side extensions can extend up to half the width of the original house, while rear extensions are generally permitted up to three meters for semi-detached or terraced houses and four meters for detached houses. Larger rear extensions may also be feasible under the larger home extension prior approval process, pending neighbour consultation. Where permitted development rights apply, we can prepare the necessary drawings and submit a Lawful Development Certificate application to the local authority to confirm adherence to permitted development rules. This process usually takes around six to eight weeks and provides formal confirmation from the council that your extension can be built without full planning permission. If permitted development does not apply, we will develop your proposal as part of a standard planning application to ensure that the design offers the best chance of approval. For more detailed guidance on permitted development rights for residential extensions, you can refer to the Planning Portal’s interactive guide: https://www.planningportal.co.uk/permission/common-projects/extensions.

Once the planning strategy has been established, CADGUYS will agree on a design fee that covers the preparation of the measured survey, planning drawings, and planning submission for residential extensions. We can typically arrange a site visit within about one week of confirming the appointment, during which we conduct a measured survey of the existing property and its surrounding context. Utilizing this information, we collaborate closely with the homeowner to refine the layout of the extension, exploring various design options and iterating on the proposal to achieve the desired space and appearance. Initial planning drawings are usually prepared within approximately three weeks of the survey, after which the client may review the design and request any necessary adjustments. Allowing for about one additional week for amendments, the drawings can then be set for submission to the council.

If the proposal qualifies under permitted development, we generally submit a Lawful Development Certificate application, which typically involves a decision timeframe of six to eight weeks. In cases where a full planning application is required, decisions are often made within ten to twelve weeks, although some projects may necessitate additional supporting surveys depending on the specific site and local authority requirements. In certain instances, councils may request further information such as ecological surveys or other technical reports before granting approval.

Once the extension has received planning approval, the project moves into the technical design stage, where the focus shifts from concept to construction. At this stage, CADGUYS develops a full set of construction drawings that translate the approved design into a detailed and buildable package. This process typically involves consulting with a structural engineer to establish a planning strategy for new openings, foundations, and structural supports required for the residential extensions. We also review existing drainage arrangements, ensuring that any new kitchens, bathrooms, or utility spaces can connect appropriately to the existing drainage system. Where public sewers are present, it may be necessary to consult the local water authority and obtain build-over approval. The construction drawings will then be developed to demonstrate full compliance with building regulations, including insulation performance, structural design, ventilation, drainage, and weatherproofing. The final package includes detailed plans, sections, and construction details outlining materials, build-ups, and technical requirements, allowing the project to be accurately priced and constructed with minimal ambiguity during the build stage.

Once the construction drawings are complete, the project transitions into the tendering stage, where contractors are invited to price the works. CADGUYS collaborates with a diverse array of trusted construction professionals and can typically recommend three to five suitable contractors who may be invited to tender for the residential extensions project. Although clients have the option to approach contractors independently, CADGUYS can also manage the tender process on your behalf, issuing the full drawing package and requesting formal quotations from each contractor. Once the prices are returned, we assist in reviewing the submissions and comparing them based on factors such as cost, programme, construction experience, and suitability for the specific build type. This planning strategy is crucial to ensure that the scope of work is clearly understood, and that contractors are pricing the same information, thereby reducing the risk of misunderstandings, variations, or disputes during the construction process.

Once a contractor has been selected, the project moves into the construction phase. At this stage, a formal building contract is usually established, often utilizing a JCT contract. This contract outlines a clear framework for both the client and contractor, ensuring the project is delivered as planned. CADGUYS can assist with contract administration and project support, helping to organise schedules of work, monitor progress, and advise on staged payments throughout the build. We also provide project management services, including periodic site visits to ensure the construction aligns with the approved drawings, the agreed specification, and the budget. Acting as a point of coordination between the client and contractor minimizes misunderstandings and keeps the project moving smoothly. When it comes to residential extensions, choosing an experienced contractor with a proven track record is essential. We always recommend reviewing previous projects and speaking with past clients before making a final decision. With the right team in place and a clear planning strategy, the goal is to deliver a high-quality home that performs efficiently, is built to last, and provides a comfortable living environment for years to come.