Home Extensions made easy…

Our SIP Extension Kits make life easier for you.

extension kitz

Welcome to Extension Kitz

Build it faster, stronger, warmer and smarter

Here at Extension Kitz we manufacture and supply quality single storey Home Extensions, Garden Rooms and Pods for both the trade and the domestic market.

Our Structural Insulated Panels (SIPs) extension kits offer builders and homeowners a design and supply solution for extending residential properties to the rear, to the side or as a stand-alone extension, quickly, efficiently and cost effectively.

We also create and manufacture extensions with our SIPs for schools.

Create additional space in your home with our SIP extension kits

stunning conservatory conversion interior light shining

Constructed under controlled conditions in our 40,000sq ft factory, our SIP extensions are tailor made specific to your individual requirements, delivered to site ready for installation by ourselves or one of our preferred installers.

Whether you want a larger living room, kitchen, or dining room, or you’re planning to add a new downstairs bedroom, playroom, bathroom, study, or annexe, we have the expertise to build your dream extension seamlessly, quickly and tailored exclusively for you.

Manufactured by us, installed by ourselves, or one of our preferred installers.

Your dream home extension can become a reality in a far shorter time than via traditional building methods.

The SIPs Panel System from Extension Kitz

Structural Insulated Panels (SIPs) are being used more often for house extensions, Garden Rooms, Home Gyms and Home Offices as people look to make their homes eco-friendly, thermally efficient, and durable.

SIP panels consist of a Liquid foam injected under high pressure to form an insulating foam core which is sandwiched between two structural facings, typically oriented strand board (OSB). SIPs can be fabricated to fit nearly any building design. The result is a building system that is extremely strong, energy-efficient and cost-effective.

Our SIPs are typically 1220mm wide and can be as long as 5.1 metres in length to suit each individual project.

These SIPs are connected with a unique jointing system for both the walls and the roofs. SIPs are fabricated using timber from sustainable sources. SIP constructions use less timber than typical timber frames and are one of the most economical and eco-friendly forms of construction.

Single storey buildings such as lean-tos, orangeries, home office buildings, annexes, garden rooms, home gyms, and summer houses are becoming more and more popular as solutions to the needs of the modern family.

Our Extension Kitz product makes full use of SIPs panels so that you and your client can have the extension that is right for you.

SIP cross section
Structural Insulated Panel cross-section

The Benefits of the SIPs System

SIPs are light yet much stronger than traditional build and can often just rest on existing foundations providing they are approved for this type of building. Most people tend to opt for concrete bases.

In these situations, SIPs can help save money because it reduces the potential costs of substructures, structural steelwork as well as the need for load-bearing internal walls. The SIP walls are slimmer than traditional build so, providing more useable space. And both the roof and walls are more thermally efficient with a U-value of 0.15 being standard.

Foundations need only be a simple concrete base. They are sometimes on existing bases when transforming a conservatory into an extension.

SIPs have excellent fire resistance and generally will exceed British Fire Safety regulations. And as a bonus, because they are made from foam, they are not susceptible to pests either.

The structure can be up and watertight in just a few days. Once built, SIP Structures are three times stronger than your average brick build, or seven times stronger than timber framed buildings.

Choose from an exterior of brickslips, cladding or render.

  • Faster Installation – SIP panels are manufactured in our factory to the exact dimensions of the extension, delivered to site ready for erection.
  • Warmer higher U-value as standard – SIPs are airtight in construction, compact with a U-value of 0.15 as standard.
  • Eco-friendly – much better for the environment.
  • Little disruption on site – Constructed in our factory, so creating less issues on site and less labour is required.
  • Enhanced Structural Performance – The intrinsic construction of SIP panels offers strength and stability which is 3x stronger than traditional build.
Externally Finished
Render and bi folds

Why use Extension Kitz

  • Skilled experienced staff fabricating our SIPs system in our 40,000sqft purpose-built factory.
  • Project managed from design to build, and installation where required.
  • Our technical support team is always at hand should installers have any queries.
  • R & D arm to design new products and improve existing offerings.
  • Range of products – SIP panels, Home Extension Kits, Pods, Garden Rooms, Annexes, Modular Educational Buildings, Cinema Rooms. Extension to a building or Stand Alone.

What are SIPs?

Constructed under controlled conditions at our factory, our Structurally Insulated Panels (SIP) Extensions have a high strength-to-weight ratio allowing large sections of your extension to be fitted at once, speeding up the time required on site.

The SIPs are typically 1220mm wide and can be as long as 5.1 metres in length to suit each individual project.

These SIPs are connected with a unique jointing system for walls and roofs. SIPs are fabricated using timber from sustainable sources. SIP constructions use less timber than typical timber frames and are one of the most economical and eco-friendly forms of construction.

SIPs are
revolutionising the way you think about
extending your home.

Our Extension Kitz

Find inspiration for your project – browse our gallery of completed work.

How we do it

base with damp proof membrane, underfloor insulation, and steel mesh ready for concrete to be poured on top.

Stage 1: The ground is dug out to the required depth, damp proof membrane, underfloor insulation and steel mesh are installed ready for concrete pouring.

Cement Base

Stage 2: Once the concrete is poured and levelled it is left for approx 72 hours to set depending on the weather. Once set work can begin.


Stage 3: Wall plates, base plates, membrane, and starter timbers are installed, followed by the SIP panels and splines. If the roof is a SIP roof this will also be constructed.

Framework going up.

Stage 4: Framework is constructed for windows, doors and roof if it is an aluminium roofing frame. Work begins on installing tiles, wrapping and battens.


Stage 5: The roof is completed with your choice of tiles. The installation of the Brick Slips begins. We have a wide range of finishing options to match your home. Glazing and doors are installed.

How we do it stage 6

Stage 6: Installation of Brick Slips is completed and pointed to give the look and feel of a brick build. Your SIP extensions is completed in a fraction of the time taken for a conventional build and with minimum fuss.

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 costs 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

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