Expert Guide to Two-Storey Extensions by McTernan Design

When planning a two-storey extension, it's essential to understand the available planning application options. These include permitted development rights and planning permission.

1. Permitted Development Rights: Permitted development rights allow some extensions without planning permission if they meet specific criteria. For two-storey extensions, this typically includes restrictions on height, depth, and proximity to boundaries. For example, the extension must not exceed 3m in depth and must not be taller than the existing roof eaves. Additionally, the materials used must match the existing property, and the extension must not be built forward of the principal elevation.

2. Planning Permission: If your extension does not qualify under permitted development rights, you must apply for planning permission. This process involves submitting detailed plans and justifications to the local council, which will assess whether the proposed extension meets local planning policies and guidelines. Planning permission can take several weeks to obtain and may involve public consultations and amendments to your plans. McTernan Design will act as your agent to navigate the planning process smoothly.

Regardless of planning permission, approval of building regulations is mandatory for any extension work. Building regulations ensure the extension is safe, structurally sound, and energy-efficient.

1. Full Plans Application: This involves submitting detailed architectural drawings and specifications to your local authority or an approved inspector. The plans will be thoroughly checked to ensure compliance with building regulations. This process provides greater certainty that the work will meet all necessary standards. It covers aspects such as structural stability, fire safety, ventilation, and energy efficiency.

2. Building Notice: For simpler projects, you can submit a building notice requiring less detailed information upfront. However, this method involves more on-site inspections and can lead to higher risks of non-compliance issues during construction. Elements of work that could have been clarified in advance using the Full Plans application pathway can become very expensive to rectify on-site once building work has started. In addition, one contractor's quote may have anticipated this detail whereas the 'cheaper' quote you opted to accept did not. Suddenly, there is a significant variation between the two quotes.

A two-storey extension can accommodate various room usages, enhancing the functionality and comfort of your home.

• Ground Floor: The ground floor of a two-storey extension is typically used for communal spaces such as kitchens, dining rooms, living rooms, or home offices. These areas benefit from open-plan designs and large windows that maximise natural light and create a spacious, airy environment. To enhance usability, consider incorporating features like kitchen islands, built-in storage, and flexible living spaces.

• First Floor: The first floor can be used for private spaces such as bedrooms, bathrooms, nurseries, or additional living areas. This layout provides a clear separation between communal and private spaces, improving your home's overall flow and usability. En-suite bathrooms, walk-in closets, and dedicated study areas can add luxury and functionality to the upper floor.

Understanding the costs associated with a two-storey extension is crucial for effective budgeting and planning.

• Average Cost: The average cost of a two-storey extension in the West Midlands ranges from £1,650 to £4,000 per square metre (plus VAT where applicable). The lower end of the cost scale includes basic construction but excludes high-end finishes and custom features. It's essential to obtain detailed quotes from contractors and account for any additional expenses that may arise during the project.

• Materials: The choice of materials can significantly impact the overall cost. Common materials include brick, timber, and metal cladding. Each material has its own cost implications and maintenance requirements. For example, reclaimed timber and eco-friendly materials may have higher upfront costs but offer long-term benefits in terms of sustainability and aesthetics. Consider materials' durability, maintenance, and aesthetic appeal when selecting.

• Labour: Labour costs include fees for builders, architects, and structural engineers. Skilled tradespeople are essential for ensuring the quality and safety of the extension. Labour costs can vary based on the complexity of the project and the expertise required. It's vital to work with reputable professionals who have experience with similar projects.

If you're extending on a tight budget, anticipate costs between £1,650 and £2,100 per square meter for a basic quality finish.

For a good quality double-storey extension, expect to pay between £1,830 and £2,350 per square meter.

For a high-spec extension, plan to spend between £2,150 and £3,500 per square meter.

A two-storey extension

Several factors can influence the overall cost of your two-storey extension.

• Size - The larger your new extension, the higher the cost due to the additional materials required and the increased effort to complete the expanded floor space.

• Quality - The quality of materials used and the workmanship will significantly impact the overall price of your two-storey extension.

• Finish - Whether you need your new extension to be plastered or painted will incur extra costs.

• Groundworks - Foundations and groundworks are essential and vary from project to project. Depending on your current situation, these costs can differ considerably.

• Scaffolding - Due to health and safety requirements, safe working at height regulations must be followed. In most cases, this necessitates scaffolding, which should be included in your budget, especially for a two-storey extension.

• Insurance - It is crucial to inform your home insurance company of any structural changes to your home, which may affect your premium. Without an up-to-date policy, you may not be covered for any accidents or damage.

• Location - The location of your home within the country, as well as the specific site of your new extension, will influence the cost of your two-storey extension.

• Drainage - Bathrooms and kitchens require proper drainage to ensure waste is appropriately managed. The additional work for this will increase the overall cost.

• Electrics - Essential for any extension, even small power points must be installed and inspected by a qualified electrician, incurring additional costs.

• Purpose of the Room -Bear in mind that adding a new kitchen or bathroom is more expensive than a bedroom due to the required electrics, plumbing, and finish. A new kitchen or bathroom may add £7,000 – £10,000 to the project.

• Windows and Doors -Adding windows and doors to your new extension can increase light and improve access. Higher quality products and extra enhancements can significantly raise the overall cost of your two-storey extension.

• Stairs - Adding stairs to a new extension is crucial for easy access. Depending on the complexity of the installation, you can expect to add an additional £2,750 to your build cost.

• Openings to Outdoors - Any doors providing access to the outside must be secure and adequately insulated, likely affecting the cost.

• Double Storey Extension Hourly Rates - Specific costs such as architect or surveyor fees and planning permissions are fixed. However, here are the hourly rates you can expect:

• Builders - Builder hourly rates vary, but generally, you can expect to pay around £35 per hour.

• Unskilled Labour: £100 per day.

• Plumbers: Between £30 – £50 per hour.

• Electricians: Approximately £45 per hour.

Constructing a two-storey extension involves several key stages, each with its own set of tasks and timelines.

1. Design and Planning: This stage involves developing detailed plans, obtaining necessary permissions, and finalising the design. It typically takes around 3 months. Collaborate with architects and planning consultants to create a design that meets your needs and complies with local regulations.

2. Site Preparation: Clearing the site, setting up temporary facilities, and laying the foundations. This stage is critical for ensuring a stable and secure base for the extension. Proper site preparation can prevent future structural issues and delays.

3. Structural Work: Building the frame, walls, and roof. This stage involves significant construction work and usually takes 14-16 weeks. Ensure that all structural elements are built to code and meet safety standards.

4. Internal Work: Installing plumbing, electrics, insulation, and interior finishes. This stage focuses on making the extension habitable and functional. High-quality workmanship is essential to ensure the longevity and comfort of the space.

5. Final Inspection: Obtaining the completion certificate from the building control authority to ensure all work complies with building regulations. This final step verifies that the extension meets all required standards and is safe for occupancy.

Achieving a successful two-storey extension involves careful planning and execution.

1. Initial Consultation: Discuss your requirements with an architect to understand the feasibility and options available. This consultation helps outline your goals, budget, and design preferences.

2. Design Phase: Work with your architect to create detailed plans that meet your needs and comply with regulations. This phase involves developing architectural drawings, specifications, and design concepts.

3. Planning Permission: Submit your plans to the local council and obtain the necessary approvals. This process may involve revisions and public consultations to address any concerns or objections.

4. Building Regulations: Ensure your plans comply with building regulations and obtain approval. This step involves detailed technical drawings and specifications to meet safety and construction standards.

5. Construction: Begin the building process, following the agreed timeline and specifications. Regular site inspections and progress meetings ensure the project stays on track and any issues are promptly addressed.

6. Final Inspection: Obtain the completion certificate to confirm that the work meets all necessary standards. This final approval ensures the extension is safe, functional, and ready for occupancy.

Different house types present unique challenges and opportunities for adding a two-storey extension.

1. Detached Houses: Detached houses offer the most flexibility for extensions, with fewer constraints from neighbouring properties. This allows for larger and more complex designs. Detached houses can accommodate rear, side, or wrap-around extensions, providing ample opportunities for creative and functional layouts.

2. Semi-Detached Houses: Semi-detached houses require careful consideration of symmetry and neighbour impact. Extensions on the non-attached side are generally more straightforward. Ensuring that the extension does not overshadow or negatively impact the attached neighbouring property is important.

3. Terraced Houses: Terraced houses are limited to rear extensions due to shared walls. Creative design solutions are needed to maximise space and light while respecting neighbours' privacy. Rear extensions for terraced houses can create additional living space without significantly altering the property's exterior.

Engaging professional services is essential for a successful extension project.

• Structural Engineers (essential): Structural engineers charge around £1,500 for their services, which include structural calculations and ensuring the extension's stability. They assess the load-bearing capacity and design the necessary structural elements to support the extension.

• Party Wall Surveyors (only required if your neighbour has concerns): Fees range from £1,000 to £1,800 per neighbour. Party wall surveyors manage agreements with neighbours when work affects shared walls. They ensure that construction work near the boundary is conducted safely and minimises disruption to neighbouring properties.

Party wall agreements are necessary when your extension affects shared walls or boundaries.

• Notification: Notify your neighbours about the planned work. Early communication helps address any concerns and ensures that neighbours are aware of the construction timeline.

• Surveyor Appointment: Appoint a party wall surveyor to handle agreements and disputes. The surveyor assesses the impact of the construction on shared walls and negotiates terms with neighbours.

• Agreement: Finalise the agreement to proceed with the construction. The agreement outlines the terms and conditions, including any measures to mitigate disruption and protect neighbouring properties.

Designing a two-storey extension involves selecting features and finishes that enhance the space and meet your needs.

• Roof Types: Pitched roofs are traditional and match the existing house. Flat roofs are modern and suitable for eco-friendly green roofs. Consider different roof types' aesthetic appeal, maintenance requirements, and energy efficiency.

• Doors: Bi-fold doors create a seamless transition between indoor and outdoor spaces. Sliding doors are space-saving and provide wide openings. Choose door styles that enhance natural light and improve accessibility.

• Interior Finishes: High-quality materials such as hardwood flooring, bespoke joinery, and premium fixtures enhance the extension's aesthetic appeal and durability. Consider the overall design theme and select finishes that complement the existing property.

• Family Spaces: Create open-plan living areas that promote family interaction and maximise space. Consider adding features like kitchen islands, large dining areas, and comfortable seating zones. Open-plan layouts can enhance the sense of space and create a versatile environment for various activities.

Understanding the significant costs involved helps you budget and plan your extension.

• Foundations: Costs vary based on soil conditions and the complexity of the site. Foundations are critical for the stability and longevity of the extension. Ensure the foundation design suits the soil type and site conditions.

• Structural Elements: Beams, columns, and walls are essential for the structural integrity of the extension. High-quality materials and construction techniques ensure durability. Structural elements must meet building regulations and provide adequate support for the additional floor.

• Fitting Out: Costs for kitchens, bathrooms, flooring, and decoration can vary widely. Investing in high-quality fittings enhances the value and functionality of the space. Consider energy-efficient appliances, durable flooring, and stylish fixtures to create a comfortable and attractive living environment.

The final stage involves fitting out and finishing the extension to make it habitable and aesthetically pleasing.

• Plastering and Painting: Ensure smooth and durable walls with high-quality plaster and paint. Professional plastering and painting create a polished and refined appearance.

• Flooring: Choose durable and attractive flooring materials such as hardwood, tiles, or carpet. Consider the durability, maintenance, and aesthetic appeal of different flooring options.

• Kitchen Installation: Install a modern, functional kitchen with high-quality fittings and appliances. Custom cabinetry, energy-efficient appliances, and stylish countertops enhance the kitchen's functionality and appearance.

• Bathroom Fittings: Install premium fixtures such as baths, showers, sinks, and toilets for a luxurious bathroom experience. High-quality fittings and finishes create a comfortable and inviting bathroom space.

Carefully planning the position of new stairs is crucial for efficient space utilisation and accessibility.

• Central Location: A central staircase provides easy access to all rooms and creates a natural flow between floors. Consider the placement of the stairs to ensure they do not disrupt the layout or block natural light.

• Design Considerations: Consider the design and style of the staircase, ensuring it complements the overall aesthetic of the extension. Options include straight, spiral, or L-shaped stairs, each with its own benefits and space requirements.

Deciding whether to move out during construction depends on the extent of the work and your tolerance for disruption.

• Significant Disruption: If the construction involves major structural changes and extensive internal work, moving out may be the best option to avoid inconvenience and ensure safety. Temporary accommodation can provide a more comfortable living environment during construction.

• Temporary Arrangements: Consider temporary accommodation options such as renting a nearby property or staying with family and friends. Plan for the duration of the construction and ensure that your temporary living arrangements suit your needs.