Self Build Extension Kits

Introducing SipSet’s Self Build Extension Kits – New, Modern, Fully Inclusive Self Build House Extension Kits.

SipSets – Transforming the way House Extensions are built!

Faster

Build in weeks not months, you are in control, book in the specialists you need, when you need them.

Cheaper

Save on labour by doing most of the work yourself. Full instructions supplied with how-to handy guides.

Thermally Efficient

25% more thermally efficient than a standard brick and block, steel or conventional timber frame build.

Satisfying

Knowing YOU did it is a very satisfying feeling. Plus it’s easier than you think! Full instructions included.

Not all House Extensions are built Equal

House Extensions – Below is data taken from the current building regulations covering England, they were modified in June 2022. UValue is a term used to display thermal performance, the lower the UValue the better.

	Notional Extension to Current Building Regulation Standards	SipSet Extension	SipSet Performance
Walls	0.18 UValue	0.12 UValue	+50%
Roof	0.15 Uvalue	0.11 Uvalue	+25%

With a SipSet Self Build House Extension Kit you get everything you need to build the perfect extension in one kit. All you need is a base and internals to finish it off.

Walls Roof Doors & Windows Roof Covering Roof Glazing Timber Tools Structural Design How-to Guides Delivery

Fully insulated structural wall panels, Uvalues = 0.12

Footprint 200mm

Breathable membrane, battens and a choice of external cladding with 8 colours and 2 finishes

or

Can be bricked up once built (not included)

or

You can supply and fit your own choice of building covering.

Fully insulated structural Roof panels, Uvalues = 0.11

Footprint 225mm

Choice of a flat roof orangery style with or without glazed roofing lanterns

or

A pitched roof with or without Velux style opening roof windows

Choice of Aluminium Bifolding or Sliding Patio doors

or

UPVC Sliding Patio or French Doors

Aluminium or UPVc Windows

Single Glazed or Triple Glazed

UValues from 0.9

Choice of colours and finishes to suit your needs

Flat roofs – Premium EPDM roof covering for flat orangery style roofs including all upstands, fascia and guttering.

or

Pitched Roofs – Lightweight slate effect roof tiles (supplied) or you can fit concrete roof tiles to match your home (not supplied). Fascia and guttering included.

Flat Roof – Glazed roof lantern with solar reflecting, low maintenance (also termed self cleaning) energy efficient glazing.

Pitched Roof – Choice of manual or electric remote controlled opening roof vents.

Full Timber kit including all structural timber members, battens and sheeting required for your bespoke design

All structural timbers are C24 grade kiln dried timber

We know not everyone will have all the specialist tools needed to build their own house extension. The job is easier if you have the right tools. Click Here to check out tools on Amazon that might help

Therefore we offer a Tool Kit hire package. The tool kit will include everything you need to make the build as easy as possible, from skill saws to SDS drills to set squares and marking pencils.

All projects come with a full set of structural design calculations to satisfy building control.

Each project is carefully designed to meet your needs and those of the building control regulations ensuring your project can be signed off without any worries.

A comprehensive set of how-to guides is included along with telephone / video call support to help you overcome any issues you may face. The guides will cover generic situations along with any additional requirements of your specific house extension kit.

When you buy a SipSet house extension kit, we will be here for you to help and guide you through the build. We will even visit site if needed and help you overcome any problems you may be facing (note additional fees may be incurred).

Your project with us does not end at the checkout, we want you to succeed so we will do all we can to help, advise and guide you through the build process until you have completed your dream self build home extension project.

Delivery is included with every SipSet House Extension kit.

During the delivery, we will explain what every item is and how to store them. We will help you organise your work area and point you in the right direction to get you started.

The delivery time will be arranged at a convenient time for you and it will not be rushed.

Depending on you, because it is you that is going to build this extension, the walls and roof can easily be built in one to two weeks, you can have a watertight structure up in far less time than a conventional brick and block build. Plus you have our support, so if you get stuck you can always call us and we will jump on a call or a video call and guide you.

We do offer hands on assistance if required in differing levels of assistance for example you can have help to build the shell, typically one week or help building the shell and fitting the roof covering and lantern/s if requested typically 2 weeks, be sure to ask when you enquire.

The aim is to empower you to build your own extension but fear not we have you covered if you need help. If you do decide to go it alone and get really stuck we can come to site and help out (fees will apply for site visits).

Add Value as well as Space with a SipSet House Extension Kit?

Did you know House extensions add value as well as space to your home? Take a look below, both houses are identical and on the same road, one without an extension and one with an extension.

Without an Extension

With an Extension

As you can see from the above house extensions add value to a home, approximately £51,000 in the example above. Address details can be supplied to prove the above, but you can check on Zoopla for historic house prices in your area. Both the above are 3 bedroom detached houses in the Peterborough area.

Build a SipSet Extension and get more floor space!

Current UK Building regulations dictate walls, floors and roofs need to achieve a certain thermal value, it is called a UValue, the table below shows the target UValues as of 15th June 2022. Conventional building (brick and blocks) need to be approx. 380mm thick!

As an example a new external wall for an extension in England would need to achieve a UValue of 0.18, that would entail building a wall with a 150mm fully insulated cavity, see the table below courtesy of Knauff Insulation

As you can see from the above, to achieve a wall UValue of 0.17 the wall would need to be 380mm thick, that is inside space you could do better things with!

A SipSet Extension has a finished wall thickness of just 285mm and it outperforms the thermal performance of a traditional wall construction by almost 50% which equals more space and less energy to warm it up.

Easy Payments for Self Build Extension Kits!

It’s free to enquire, then once you decide to proceed we only ask for a small (up to a 20%) deposit. We will then arrange a remote site inspection or if needed a physical site visit (most initial site inspections can be done remotely). Once we have gathered the information required and agreed on a design.

If required we will arrange for planning permission to be sought on your behalf. Planning permission is required if your design is projecting more than 4m from the property’s back wall for a detached property and 3m for all other property types.

If planning permission is not required we will instruct our structural engineer to specify the extension for Building Control Regulations compliance. If planning permission is required we will wait until permission is granted before instructing our engineer.

When we have the final detail from our structural engineer, we will issue you a base plan and if requested, register the project with Building Control. You or your builder will then construct the base to the satisfaction of building control.

Once the base plan is issued, or final designs and specifications are agreed upon, we ask for the balance of your kit price.

All this is included in your SipSet self-build house extension kit:- Design, Planning (if needed), Structural Engineering, Building Control Registration (if requested), Walls, Roof, Doors and Windows, Cladding, Timber and the many fixings you will need to complete the build. Not forgetting the handy “How-To” guides plus phone support if you need it. So if you are asking yourself can I build my own extension? With a kit from SipSet it will certainly make it easier for you, after all we want this to be a very easy and fully inclusive service for you!

Find out who we are by taking a look at our About Us page

Take a look at our recent articles…

Self Build Extension Oxfordshire – Isaac

7 July 2025

Isaac wanted to self build an extension for his family home in Oxfordshire. It started, as ever, with a quick site photo and some initial plans, Isaac had architect plans, but a hand-drawn sketch would have worked just as well. This led to some questions… Once we had an idea of the direction Isaac wanted …

Read more

Can I Build My Own Extension?

11 May 2023

Can you build your own extension? Read our comprehensive guide and find out what it takes to build your own extension.

Self Build Extension Kits: UK Homeowners’ Essential Guide

19 April 2023

Discover the essential guide to self build extension kits for UK homeowners, covering various approaches, customisation options, and key factors to consider.