Are Cantilever Extensions Worth It? Design, Cost & Reality

Quick Summary

Cantilever extension gives you stylish, space-saving rooms or side extensions without compromising on any ground space. It is a blending of modern design with practical use. In the UK, the price is usually between £2,500 and £4,000 per square metre; the final cost depends on size, complexity, and choice of materials.

Are you looking for an extension that looks modern in architectural design and feels functional in terms of space without compromising on outer garden space? Then this extension is specifically picked for you.

A cantilever extension is a house extension that extends out beyond the outer wall of the house with no visible supporters underneath. Rather, it is secured by precision-designed structural components within the existing building.

If you need a bit more room but don’t want to give up any garden space, or you’re after a bold, modern look, a cantilever on a house may be just what you’re looking for. Enjoy your outdoor space to the fullest. Having breakfast or evening tea with this type of extension can give you all.

From sleek side extensions to breathtaking top-floor spaces, cantilever designs prove that practicality and architectural drama are not mutually exclusive.

What is a cantilever extension?

A cantilever is the projection of a structural element, such as a balcony, over a space or void beyond the plane of support of the main body. A cantilevered house extension is an addition that projects out from the external wall of a home, being supported internally without columns or walls beneath it.

In layman’s terms, the extension “hovers” above the space below, often over a driveway, patio, or room on a lower level. 

• First-floor cantilever room extension. 
• Cantilevered side extension to widen narrow houses. 
• Contemporary cantilever roof extension design solutions for additional bedrooms or home offices. 

This style of design is particularly sought after in city homes where there is little or no ground available.

Key Advantages of a Cantilever Extension

Choosing a cantilever house design offers numerous advantages:

• Maximises usable space without increasing ground footprint 
• Preserves outdoor areas, such as gardens or parking spaces
• Creates a striking modern aesthetic 
• Allows for an open-plan layout and large glazed sections
• Adds property value when designed correctly. 

For homeowners looking to extend creatively, a cantilever offers flexibility that traditional extensions often can’t. 

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Brilliant Ideas for a Cantilever Extension

Here are some of our favorites, and the most practical designs include:

• Cantilever side extension over a driveway for an extra bedroom
• Cantilevered first-floor room extension to expand a master suite
• Cantilevered roof extension, glass-heavy for a light-filled home office
• Rear cantilever creating a bold architectural statement over bi-fold doors
• Kitchen extensions that cantilever over patios to create a seamless indoor–outdoor flow.

Meaning that each of these ideas combines contemporary design with clever space-saving.

Issues that arise when installing a cantilever extension

While visually impressive, cantilever extensions come with challenges:

• Complex structural engineering requirements
• Higher reliance on steel beams and load calculations
• Possible disruption to the existing structure during installation
• Increased build time compared to standard extensions
• Greater need for experienced designers and builders

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Is the cantilever design of the home more expensive?

Yes, in most cases, a cantilever house extension will cost more than a traditional extension, as it needs more advanced structural solutions. This higher cost always stems from the application of substantial structural steelwork, specialist engineering design, skilled labor, and detailed inspections and load calculations to guarantee safety and compliance. 

However, even with that extra outlay, a lot of homeowners find the additional cost worthwhile for the increased design options, space efficiency, and the stunning visual impact a cantilever design provides to a home.

How much does the cantilever extension cost?

The cantilever extension cost in the UK typically ranges from £2,500 to £4,000 per square metre, with the final price depending on several factors such as the size and complexity of the build, structural requirements, materials used, site location and access, and the level of architectural detailing involved. 

A simple cantilever side extension is generally more affordable, while a multi-storey cantilever roof extension with extensive glazing and bespoke finishes will sit at the higher end of the cost range.

Planning Your Cantilever Extension

A cantilevered addition isn’t just an architectural extravagance; it’s a clever space-saving solution, which allows you to expand your living area and add flair to your home without giving up precious outdoor space. It may mean additional costs and high-level expert planning, but the benefits make it an investment worth making: design freedom, impressive aesthetics, and additional property value. 

If you want to make your vision of a cantilever house extension a reality, speak to a Paramountbuilt architect or structural engineer today and begin designing the home of your dreams.