Extensions Andover & Hampshire
Expanding your home is one of the most exciting improvements you can make, whether you dream of a spacious open-plan kitchen, a dedicated home office, or a light-filled dining room. However, finding a builder you can truly trust is often the hardest part of the process. The fear of delays, mess, and the “subcontractor merry-go-round” puts many people off starting their project.
At KJM Group, we do things differently. Unlike many double glazing companies that farm out building work to the lowest bidder, we employ our own dedicated building team.
From the initial foundations to the final plastering, your project is managed entirely in-house by KJM experts. This ensures total accountability, higher quality control, and a smoother experience for you and your family. Whether you choose a traditional brick build or a high-performance Ultraframe system, we handle the entire project from concept to completion.
Why Choose KJM to Build Your Extension?
- No Subcontractors: We use our own salaried, employed building team. We don’t rely on random “subbies,” so you know exactly who is in your home.
- One-Stop Shop: We manage the full project—including electrics, heating, and plastering—so you don’t have to juggle multiple trades.
- Next-Gen Efficiency: We specialise in modern extension systems (like Ultraframe) that are up to 5x more thermally efficient than older builds.
- 10-Year Warranty: Fully insurance-backed protection for both the building work and the glazing.
Key Product Features
Our extensions are perfect for growing families or upgrading existing homes. These precision engineered extensions are warm and welcoming throughout the year by providing additional space.
Choose between various designs to add thermal performance and regulation approved security features. Combining easy installation of windows and glazing, our masonry piers can be used to improve thermal comfort and complete the overall appearance of your extension.
Customisation Options
Working closely with Ultraframe, we can use and install a selection of their high quality extension designs. Choose from flat roof, Livinroof or Ultraroof designs to find and tailor to meet your tastes and needs.
Using these designs as bases, you can upgrade your extension by changing windows, doors, glazing designs, hardware and locking systems. Alternatively, opt in for blinds, light and speaker systems or underfloor heating. For product photographs of our installed extensions, view our product gallery.
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About KJM Group
Since 1983, KJM has been working in the Andover and Hampshire areas to provide excellent customer service and home improvement installations. With 40 years of trading history, our extensions are installed with high quality materials and years of experience.
Our partnership with Ultraframe and our Which? and Checkatrade accreditations are examples of our open, honest and personalised customer service. To find out more about our business values, visit our about page for more information.
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Extension Prices Andover & Hampshire
Use our quotation engine today to view extension prices based on size and location. We strive to provide customisability to our products as well as our extensions. Choose the glazing, windows and doors which best suit your design specifications in the Andover and Hampshire areas.
You can find the appearance that matches or compliments your existing property with our various colours, hardware and finishes. To receive a bespoke quote which meets the upgrades and additions you are looking for on our extensions, fill out our contact form for a response as soon as possible.
Frequently Asked Questions
How thermally efficient are KJM extensions?
Extremely efficient. Our extensions are designed to achieve energy ratings of up to ‘A++’, ensuring your new room is comfortable year-round. By using insulated columns and high-performance Ultraframe roofs (like the Ultraroof), we significantly lower U-values compared to standard brick builds.
What types of extension roofs are available?
We partner with Ultraframe to offer a versatile range. You can choose a Flat Roof for a contemporary look with skylights, a ‘Livinroof’ which combines solid panels with glass for the best of both worlds, or the ‘Ultraroof’—a lightweight tiled system that mimics a traditional roof while boosting thermal retention.
How secure are your extensions?
Security is a priority. All windows and doors fitted to our extensions come with multi-point locking systems and shoot-bolt mechanisms as standard. This ensures your new space meets strict security standards, giving you total peace of mind.
What glazing options can I choose?
You can fully customise your glazing. We offer high-performance double or triple glazing to maximise thermal efficiency. You can also specify privacy glass for overlooked boundaries or solar-control glass to prevent overheating in south-facing extensions.
How long will my extension last?
Our extensions are built to last for decades. We use premium materials that are rigorously tested for durability and weather resistance. For added reassurance, every installation comes with our comprehensive 10-year insurance-backed warranty.
How much does a house extension cost?
Costs vary depending on size, roof choice, and finishes. We offer an online quotation engine for a quick standard estimate. However, if you are looking for a bespoke design with specific windows or doors, please contact us for a free site survey and a fixed-price quote.
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Awards and Accreditations
