Get a Quick Quote today

Fill out the form and give us brief details.
We will get back to you with an indicative SIPs extension cost, so you know what to expect.
Once you have an idea of the price of a SIPs extension, you can then make an informed decision.

Or call the experts today on 0330 166 0877

Maximise Your Space with SIPs

Traditional cavity wall construction typically uses up to 350mm of wall thickness, which can eat into your usable floor space—especially in smaller extensions. In contrast, SIPs (Structural Insulated Panels) use just 147mm of thickness while still exceeding modern insulation and strength standards.

In a 4m x 5m extension, this difference alone can free up around 2m² of additional internal space—enough for extra storage, a larger dining area, or simply a more open feel. With SIPs, you’re not just building faster and stronger, you’re building smarter.

Space gained with SIPs

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Annexes

Our extension kits are ideal for creating smart, warm and energy-efficient Annexe

AltTextBuild that extra space quickly

At Extension Kitz, we design and build premium SIPs annexes that offer a smart, efficient solution for multigenerational living or extra accommodation. Whether it’s for elderly relatives, growing teens, or simply a space to rent out, our annexes are warm, secure and built to last – all manufactured in our UK facility for fast, dry-fit installation.

Each annexe is fully customisable, from layout and size to cladding and interior finishes, giving you complete control to create a truly self-contained living space. With full-width bifold doors and thoughtful design, these builds offer maximum natural light and a modern finish that blends with your garden environment.

We handle the entire process – from planning support and groundworks to delivery and construction – ensuring minimal disruption and maximum quality. Built using our trusted SIPs system, your annexe will be faster, stronger, warmer and smarter.
sip cross section

Why Choose Extension Kitz?

 
UK-Manufactured SIP Panels
We work with you to understand your goals and assess your existing structure.
 
Highly Insulated and Energy Efficient
Panels are custom-made in our UK facility and fully dry-fitted for quality assurance.
 
Fully Customisable Designs
Quick, clean assembly with minimal disruption to your home life.
 
Expert Team with Years of Experience
Choose from a range of internal and external finishes to complete your dream space.
 
Quick Turnaround and Minimal Disruption
Choose from a range of internal and external finishes to complete your dream space.
versatile sip panel

The advantages of modular house extensions built with SIPs

Our modular house extensions are a cost-effective and convenient way for homeowners to add space and value to their property. The process compares favourably with other methods used in the building industry, like brick-and-mortar extensions.

  • Speed of construction

    Much of the construction process takes place off-site as the extension kits are prefabricated in our factory. This reduces the on-site construction time considerably and makes installation much quicker and cheaper than a conventional timber or masonry extension.

  • Cheaper construction with less mess

    Extension kits are subjected to stringent quality control at our factory and delivered on-site with clear assembly instructions. A prefabricated modular home extension project can be built in a few days by a small team, saving money on labour costs. As all the materials are created off-site, there is less mess and disruption for the homeowner.

  • Predictable costs

    The cost of the construction materials, the SIPs, is known upfront, so there is no chance of hidden posts or the project budget running out of control.

  • Lightweight construction

    SIPs are extremely light, making them easy to manoeuvre into tight spaces. Their low weight also means that they do not require the deep foundation that other construction methods need, again saving time and both material and labour costs. 

  • Low heating costs

    Modular extensions are gaining popularity for all of the above reasons, but their high levels of insulation and airtight build are some of the reasons that our customers love them. Modular home extensions made from SIPs keep the house warm while reducing healing costs.

  • Reduced energy costs during manufacturing and delivery

    SIPS structures are environmentally friendly throughout the entire manufacturing, delivery, and assembly process. They are manufactured with sustainable timber from managed forests, and our quality control ensures waste is kept to a bare minimum. The low weight of the panels makes them cheap to transport, reducing energy costs and benefitting the environment. 

  • Flexibility of design

    The SIPS can be cut to any design, and we can offer a range of finishes, including brickslips, render and cladding in a range of colours.

  • Superior strength

    Our SIPs panels may be light, but they are also super strong, and SIPs constructions are three times stronger than timber constructions.

Get a Quick Quote today

Fill out the form and give us brief details.
We will get back to you with an indicative SIPs extension cost, so you know what to expect.
Once you have an idea of the price of a SIPs extension, you can then make an informed decision.

Or call the experts today on 0330 166 0877

"Build it faster, stronger, warmer and smarter"

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