Flat Roof vs Pitched Roof....What’s Best for Your Extension?

Neil Heyes
Jun 20
3 min read

When designing a home extension, whether it’s a Flat Roof on a Single Storey Extension, a Double Storey Side Extension, or a Loft Conversion, the roof type you choose plays a big role in the final look, cost, and long-term performance of the build.

At Plans4Extensions, we specialise in architectural drawings, planning permission support, and permitted development plans for all types of home improvements. Here’s our expert take on the pros and cons of flat roofs vs pitched tiled roofs—to help you choose what’s right for your project.

Flat Roofs for Extensions

Flat roofs are becoming increasingly popular, especially in modern single storey rear extensions, wrap around extensions, and contemporary loft conversions.

Advantages of Flat Roofs:

– Modern, minimalist style – perfect for open-plan kitchen and garden rooms– Lower construction costs – generally cheaper than pitched tiled roofs– Quicker to build – shorter construction time can save money and reduce disruption– Ideal for height-restricted areas – great for planning rules and permitted development– Easier to incorporate skylights or roof lanterns – ideal for maximising natural light

Disadvantages of Flat Roofs:

– Shorter lifespan – typically 15 to 30 years depending on the material (e.g. GRP, EPDM, felt)– Drainage issues – standing water can occur without proper slope and outlets– Less energy efficient – more prone to heat loss if not properly insulated– May not suit traditional properties – can look out of place on older homes

Pitched Roofs for Extensions

Pitched tiled roofs are a classic choice and ideal for double storey extensions, loft conversions, or matching existing house architecture.

Advantages of Pitched Roofs:

– Timeless look – suits most UK homes and adds kerb appeal– Long-lasting – can last 50+ years with little maintenance– Superior drainage – water and snow run off easily– Better insulation options – can help reduce heating bills– May allow for additional space – vaulted ceilings or storage potential

Disadvantages of Pitched Roofs:

– Higher construction cost – due to materials and complexity– Longer build time – pitched roofs take longer to install– May require planning permission – especially if it increases the ridge height

Cost Comparison

Costs vary depending on design, materials and access, but here’s a rough guide:

Flat Roof on Single Storey Extension (GRP or EPDM): £100–£160 per m²***

Pitched Tiled Roof (Concrete or Clay Tiles): £150–£250 per m²***

***

Adding skylights, insulation upgrades or complex junctions (like on a wrap around extension) may increase these figures.

Making the Right Choice

Choose a flat roof if you want:

– A modern look that complements open-plan living, to keep costs down, to comply with height restrictions under permitted development– A quicker build time

Choose a pitched tiled roof if you want:

– A traditional, long-lasting aesthetic, better energy performance, greater roof durability and resale appeal

At Plans4Extensions, we provide professional architectural drawings and help you navigate planning permission or permitted development rules so your extension is compliant and cost-efficient.

Final Word from Plans4Extensions

Whether you’re planning a flat roof on a single extension, a loft conversion, a double storey extension, or a wrap around extension, we’re here to make the process smooth from start to finish. Our architectural design service ensures your roof design complements your home, complies with planning regulations, and stays within your budget.

Ready to get started? Let Plans4Extensions prepare your extension drawings today, so you can lock in current material costs and avoid further price increases.