House Extensions vs. Moving: Which is Right for you?

Deciding between moving to a new property or investing in house extensions is a major financial crossroads for UK homeowners. In 2026, with the high cost of stamp duty and the rising value of bespoke living spaces, many families are choosing to renovate. Extending your current home can often be cheaper and less disruptive than moving once you factor in estate agent fees and removals.

Strategic Planning

Should you build an extension or move house?

Financial Advantages

Extensions offer more affordable choices than moving.

ICF Efficiency

ICF is self-build friendly and can be used when access is restricted.

Structural & Legal

Extending existing properties requires careful consideration.

Modern Methods, Limitless Design.

Seamlessly Connect Your New Extension to Any Existing Home.

To move or build a house extension?

Pros & Cons To House Extensions

Building onto your current property allows you to stay in an area you love while tailoring a space, like a modern kitchen or a high-tech home office, exactly to your needs.

Pros: Maintain community ties, avoid stamp duty, and potentially add significant resale value.
Cons: Months of on-site disruption, potential neighbour objections, and the risk of “over-developing” the plot beyond the local price ceiling.

Pros & Cons To Moving House

Moving can provide an immediate upgrade in location or school catchment area that no amount of construction can fix. And when buying and selling a house is now such a costly and difficult process, many people are considering an extension as an alternative.

Pros: Instant access to a new layout, better amenities, and the ability to release equity in a strong market.
Cons: Massive one-off costs (conveyancing, surveys, and tax) can equal the budget of a modest extension, and you may still need to refurbish the new property anyway.

The Advantages of Using ICF for House Extensions

Building a house extension is a significant investment, and choosing the right construction method is vital for both cost and performance. One of the most efficient modern methods of construction is Insulating Concrete Forms (ICF).

The primary advantage of using ICF for extensions is that it is “self-build” friendly. Unlike traditional methods, you don’t necessarily need highly skilled bricklayers to lay heavy blocks or bricks.

Key Benefits for Your Home Extension

Beyond the ease of construction, ICF offers several technical and financial advantages for those extending their homes:

Superior Thermal Regulation: The responsive thermal mass provided by Polyblok ICF forms, combined with steel ties at close centres, ensures your new living space won’t overheat in the summer. This eliminates the need for expensive air-conditioning systems.
Logistical Ease: You won’t need to move heavy materials on pallets through narrow side-access points into the back garden—a common headache with traditional house extensions.
Cost-Effective Performance: Polyblok walls are the most economic way to create a highly insulated, noise-proof, draught-proof, and fire-resistant extension.
Versatile Exterior Finishes: Whether you prefer render, timber cladding, or brick slips, these can all be installed by a self-builder. For a professional finish on rendering, a local plasterer can easily be hired.
Structural Flexibility: Roofs can be built using a beam-and-block system by a self-builder, allowing the flat roof of your extension to be utilised as a terrace or balcony.

Construction Management

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Planning Your House Extension

Many homeowners mistakenly believe the design of house extensions is a straightforward process. In reality, connecting a new structure to an existing building requires deep structural knowledge. You must understand how the type (and condition) of the existing structure constrains the new build.

With ICF, integrating an extension to your existing property is simplified. For instance, you can attach new walls to existing cavity walls by fixing galvanised ties to the brickwork that protrude into the ICF cavity, creating a permanent, rigid fixing once the concrete is poured. Furthermore, the foundations for an ICF extension can be a simple 150mm flat slab with edge thickenings extending below the frost line (500mm), reducing the complexity of groundworks.

While Permitted Development rules often allow for detached extensions in a rear garden, these “garden rooms” may lack the seamless access required for daily family life. Furthermore, a layout that works now might fail once an extension is added; for example, adding a ground-floor bedroom for a teenager may create noise conflicts with the living room that a first-floor extension would have avoided.

So many extensions are built that simply do not work because the future use the extension has not been thought through in detail.

Technical Challenges: Underpinning & Foundations

Structural complications often arise when foundation excavations for the new build are deeper than those of the existing house. This is common with pre-war housing featuring shallow foundations. If your new foundations are near or shared with a neighbour, you must navigate the legalities of the Party Wall etc. Act 1996.

Party Wall Agreements

A Party Wall Agreement is a legally binding document required in England and Wales when work affects a shared boundary or requires excavation within 3–6 meters of a neighbour’s structure.

Purpose: It protects both parties by outlining how work will proceed safely, including access rights, working hours, and a “schedule of condition” to prevent or resolve damage claims.
Triggers: Common for loft conversions, damp proofing, new foundations and house extensions. Applies only in England/Wales (not Scotland/NI).
Process: You must serve notice 1–2 months in advance. If neighbours disagree, surveyors must be appointed to draft the final award.

The Rise of Garden Buildings

Another popular method to extend the indoor space of your property is to build a bespoke garden house. The construction process can be very straightforward when an ancillary building can be placed in the garden away from boundaries (subject to height restrictions). Especially if there is access for material delivery and export of the excavation arisings.

However, you must still provide planning quality drawings to the Local Authority to obtain a Lawful Development Certificate, confirming whether the project falls under Permitted Development.

Using ICF For Garden Buildings & Studios

ICF is equally effective for detached garden buildings, offering the same rapid construction benefits. It is particularly popular for home music studios due to the exceptional soundproofing qualities that ICF Polybloks provide.

When building an ancillary garden room away from boundaries, you can often take advantage of Permitted Development rules. This makes the design and construction straightforward, especially if there is clear access for material delivery and soil removal.

Note on Planning: Even if your project falls under Permitted Development, you should provide planning-quality drawings. Obtaining a Lawful Development Certificate from your Local Authority is highly recommended to confirm your project is legal and to avoid issues when selling your property in the future.

Conclusion

Whether you are looking to add a single-story sunroom or a complex multi-level addition, well-planned house extensions offer a bespoke alternative to the volatile 2026 housing market. By avoiding the sunk costs of moving and focusing on high-quality design, you can transform your current property into your dream home. If you are ready to increase your square footage and property value, start by consulting with a structural engineer to ensure your house extensions are built on a solid legal and physical foundation.

ICF House Extensions

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