Single Storey Extension Roof Options: A Complete Guide

Planning a single storey extension is an exciting journey toward a bigger, better home. Whether you’re considering a spacious kitchen extension or simply looking to add functional space, one of the most crucial decisions you’ll need to make is selecting from the various single storey extension roof options available to you. The extension roof design you choose will profoundly impact the aesthetics, natural light, and overall cost of your project.

At Abbey Partnership, we specialise in delivering exceptional home extensions, and we’re here to guide you through the various extension roof types available, helping you make an informed choice that perfectly suits your property and budget.

Key Takeaways

• The three main single storey extension roof options are the Pitched Roof (traditional and high-ceilinged), the Flat Roof (modern, good for height restrictions), and the Glazed Roof (maximises light via lanterns).
• A flat roof is generally the lowest initial cost option, while incorporating a large roof lantern adds significant expense.
• The maximum height for an extension under Permitted Development is four metres (or three metres near a boundary).
• All extensions, regardless of size or PD status, must comply with UK Building Regulations for insulation and structure.
• Choosing the right roof maximises natural light, improves thermal efficiency, and enhances the overall property value.

What is a Single Storey Extension?

A single storey extension is a ground-floor addition to your existing property. These extensions typically project from the rear or side of the house and, as the name suggests, only have one floor. They’re an incredibly popular choice for homeowners looking to increase living space without the complexity and cost associated with a multi-storey build. 

Common uses include:

• Expanding a kitchen into a large, open-plan kitchen-diner.
• Adding a bright, new living room or garden room.
• Creating a utility room or downstairs toilet.
• Building a dedicated home office.

Advantages of a Single Storey Extension

Choosing a single storey addition offers several compelling benefits that make them a favoured choice for UK homeowners:

• Cost-Effective: Generally, they are more affordable and quicker to build than two-storey extensions, as less complex structural work is required.
• Increased Natural Light: With the right extension roof design – especially when incorporating rooflights or lanterns – a single storey extension can flood the adjoining rooms with natural light, transforming dark areas of the original house.
• Design Versatility: The lower height allows for more creative single storey extension roof options that can contrast or complement the existing house, such as a modern flat roof or a traditional pitched style.
• Permitted Development: Many single storey extensions fall within Permitted Development rights, potentially simplifying the planning process and saving time (though Building Regulations approval is always required).

Single Storey Extension Roof Options

The roof is the crowning glory of your new extension, providing essential shelter, insulation, and character. Here are the primary extension roof types you can consider for your new addition:

The Classic: Pitched Roof

The pitched roof is the most traditional and common roof for extension projects. It features two slopes meeting at a central ridge.

• Aesthetics: Offers a seamless blend with most traditional UK homes, especially if the pitch angle and tiles match the original property.
• Practicality: Excellent for drainage and allows for greater insulation depth, often resulting in a highly energy-efficient structure. The high ceiling can also create a light, airy, and dramatic internal space.
• Adaptations: This style easily incorporates roof windows (Velux-style) to bring in light.

The Modern Choice: Flat Roof

A flat roof is a contemporary and simple extension roof type that provides a sleek, minimalist finish, popular with modern architectural styles.

• Aesthetics: Delivers clean lines and a modern profile. It’s often preferred for side return extensions where height restrictions apply.
• Practicality: Allows for the easy installation of large roof lanterns or skylights, maximising the ingress of daylight. While termed ‘flat’, it has a slight pitch to ensure effective water run-off.
• Cost: Typically one of the most cost-effective roofing solutions initially, often covered in modern, durable materials like GRP fibreglass or EPDM rubber.

The Bright Option: Glazed Roof (Roof Lanterns and Skypods)

Glass roofs, often incorporated into a flat roof structure, transform the look and feel of an extension by creating a stunning focal point and bathing the interior in sunlight.

• Aesthetics: Provides a ‘wow factor’ with uninterrupted sky views and a feeling of immense space.
• Practicality: The ultimate solution for daylight penetration. Modern glazing is highly insulated and energy efficient.
• Types: This category includes large, structural roof lanterns (often pyramidal or rectangular) and smaller, sleek Skypods or flat glass rooflights.

The Durable Option: Warm Roof Systems

While not a roof shape, a warm roof system is crucial for a flat roof’s performance. It places the insulation above the structural deck, meaning the structure stays ‘warm’ and prevents condensation issues. All our modern extensions use high-performance, well-insulated systems to meet strict Building Regulations.

Single Storey Extension Roof Costs

Providing exact costs is impossible without a site visit and a detailed specification, as prices vary greatly depending on location, roof size, material quality, and complexity. However, we can offer some indicative averages for the overall extension build, which the roof cost is a component of.

As a rough guide, a quality, mid-range single storey extension in the UK often costs between £1,800 and £2,800 per square metre of floor space (excluding VAT, high-end kitchens, and professional fees).

The roof itself typically accounts for a significant portion of the total build cost, and the choice of extension roof type will impact the final figure:

Note: These figures are highly variable. For a precise quotation, please contact Abbey Partnership to discuss your specific extension roof design and project requirements.

Single Storey Extension Roofs: Permitted Development and Planning Permission

Understanding the difference between Permitted Development (PD) and Planning Permission is vital for any extension project, especially regarding the roof structure and height.

Permitted Development Rights

Permitted Development rights are a national grant of planning permission that allows you to carry out certain building works without needing a full planning application, provided specific limits and conditions are met.

Key Roof/Height Conditions for Single Storey Extensions under PD:

• The extension’s maximum height cannot exceed four metres.
• The eaves (where the wall meets the roof) must not be higher than the eaves of the existing house.
• If the extension is within two metres of any boundary, the maximum eaves height is further restricted to three metres.
• The materials used for the roof and walls should be similar in appearance to those of the existing house.

When Planning Permission is Required

If your proposed extension roof design or size exceeds any of the limits set out by Permitted Development, you will need to submit a full Planning Application to your Local Authority. This is required if:

• The maximum height of the extension is over four metres.
• The extension extends beyond the rear wall of the original house by more than four metres (detached) or three metres (attached) without going through the ‘Prior Approval’ process for larger extensions.
• You live on ‘designated land’ (e.g., a Conservation Area or National Park), where PD rights are often more restricted.
• The planned extension would cover more than 50% of the original land area around the house.

It’s important to note that even if your project falls under Permitted Development, it must still comply with all Building Regulations. These cover the structural integrity, insulation, fire safety, and ventilation of your new roof and building. 

Why Choose Abbey Partnership for Your Single Storey Extension?

Choosing Abbey Partnership means partnering with experts who understand the nuances of building a high-quality, long-lasting extension. We don’t just build; we design and manage the entire process, ensuring your choice of single storey extension roof options is the perfect fit for your home.

Here why our customers choose us:

• Design Expertise: We provide tailored advice on the optimal extension roof design and materials to maximise natural light and thermal efficiency, whether you choose a pitched, flat, or glazed roof.
• Seamless Project Management: From initial concept drawings and navigating the complexities of Permitted Development and Building Regulations to the final handover, we offer a complete, stress-free service.
• Quality Craftsmanship: Our experienced building team use only the highest-quality materials, ensuring your new roof is durable, weather-tight, and beautifully finished.
• Tailored to You: We listen to your vision for your side extension or rear extension, ensuring the roof complements your property’s existing architecture and meets your lifestyle needs.

The Next Step for Your Extension Roof Design

The right roof is the key to a successful single storey extension. By carefully considering the various extension roof types, along with budget and planning implications, you can create a beautiful and functional space that adds significant value to your home. Contact Abbey Partnership today for a consultation to explore the best single storey extension roof options for your project and start turning your extension dream into a reality.

Single Storey Extension Roof Options: FAQs

Is a pitched roof or a flat roof better for a single storey extension?

A pitched roof is traditional, offers better drainage, and provides high ceilings. A flat roof is modern, often cheaper, and ideal for installing large roof lanterns or for side extension roof types where height is restricted.

Do I need planning permission for a roof lantern on my extension?

Typically no, as long as it doesn’t project more than 150mm from the roof plane and is not higher than the highest part of the roof. However, the extension itself must comply with all Permitted Development rules.

What is the most durable material for a flat roof extension?

Modern flat roofs are highly durable. High-performance EPDM rubber (ethylene propylene diene monomer) and GRP fibreglass (glass reinforced plastic) are both excellent, long-lasting, and low-maintenance options.

Can I walk on a flat roof extension?

A standard flat roof is built only for maintenance access. If you intend to use it as a balcony or terrace, the structure requires specific, costly reinforcement to support foot traffic.

How much does a tiled pitched roof for an extension cost?

The roof structure and covering can be 10-15% of the total build cost. For materials and installation, a pitched roof for an average extension could range from £7,000 to £16,000, depending on size and tile choice.

Does a flat roof extension need to be completely flat?

No. It must be built with a slight minimum fall (pitch) to ensure proper water run-off and prevent ‘ponding’, as required by Building Regulations.

Can I use a different roof tile to my main house on the extension?

Under Permitted Development, materials must be “similar in appearance” to the existing house. For the best look and easiest planning process, matching the original roof tiles or slate is usually recommended.

What is the maximum height for a single storey extension roof?

Under standard Permitted Development, the maximum height is four metres. If any part is within two metres of the property boundary, the maximum eaves height is restricted to three metres.