Can I Build My Own Extension?

Table of Contents:

• Terms To Understand
• Types of Extensions
  • Brick and Block
  • Timber Framed
  • SIP panel (in our opinion the best method)
• Types of Extension Roofs
  • Flat Roof
  • Pitched Roof
• Key Factors to Consider When Undertaking a Self-Build Extension Project
  • Complying with the Rules
  • Your Skill Level
  • What to Sub Out
• Conclusion

• Planning Regulations
  • Planning Permission regulations can be found on the Planning Portal it is a somewhat tricky area and if in doubt always ask first, it is far easier to do it right to start with than retrospectively correct something.
• Building Regulations
  • Always, always follow building regulations guidelines! This is fundamental to a successful build. You do not have to like the building control inspector, you don’t have to agree with them but when it comes to getting your project signed off it is them alone that will issue the certificate. Generally speaking, they are good people doing a job, work with them!
• Structural Engineer
  • A Structural Engineer is the person who will ensure your chosen design is buildable to the satisfaction of Building Control regulations. A Structural Engineer that knows their onions is invaluable!
• SAP Report
  • SAP reports let Building Control inspectors know that the building is thermally acceptable. A SAP report looks at each element of a build and determines the overall efficiency (or not) of an intended structure. SAP reports are always required for extensions that are over glazed (more than 25% of the floor area is glass) and where they are open to the host property.
• UValue
  • UValue is the figure used to determine building elements’ thermal properties, the lower the UValue the better it will perform. Building regulations often state a target worse case UValue figure that you must achieve.
• Cold Roof or Warm Roof
  • Cold Roof – While it sounds like a negative it is not! The terms referees to the positioning of the roof joists are they in or under the insulation? Cold roofs have the structural joists open to the elements. Cold roofs are generally 300mm in depth or thereabouts.
  • Warm Roofs – Have the structural elements underneath the insulation it is possible to imagine a warm roof deck being over 400mm in depth. While that might not sound a lot, a relatively small extension with a large depth of roof can look unsightly.

Types of Extensions

Brick & Block

Brick and Block – UK building regulations determine the overall foot print size of an external wall by stating a UValue. At the time of writing a standard brick and block wall will be approx 385mm thick

Timber Frame

Stick built (the common phrase used to describe a timber framed building) are a simple construction method. They involve lots of timber and timber cutting and then sheeting with OSB and then insulating. Stick building, while simple is slow, labour intensive and not as efficient as SIP construction.

Sip Construction

SIP’s are a relatively new method of construction, they are a vastly underused solution in the building industry and not generally understood by building control inspectors. We are here to help change that! SIP is short for Structural Insulated Panel generally they are insulation that is bonded to or injected between two sheets of OSB. They come in various sizes and can be cut on site to suit a build although that’s not always the best approach.

A standard ceiling height is approx 2.4m and SIP panels are available at 2440mm and 1220 mm wide making them ideal for extension construction. SIP panels require less timber which equals less timber thermal bridging. SIP panels have extremely low UValues for relatively small foot prints. A common misconception with SIP panels is the difficulty getting services (electrics and plumbing) in place, actually, extensions built with SIP panels make it easier as service voids are easily created by using battens and then plasterboarding.

We believe SIP panel Extension construction is the way forward and therefore the rest of this article will concentrate of SIP panels as the method of construction.

Types of Extension Roofs

Flat Roofs

Flat roofs are easy to construct with SIP panels, they form a cold roof so will need a little more work but the additional work needed far outweighs the height needed to form a structural roof using a warm deck approach.

Glazed lanterns can be incorporated into a SIP panel flat roof to form an Orangery style building.

Pitched Roofs

Pitched or sloping roofs can be tiled with either a lightweight tile or a tile to match the host property. They can have opening roof vents fitted which could be electric operation or manual operation.

Key Factors to Consider When Undertaking a Self Build Extension Project

Complying With The Rules

When you undertake a building project there are many things to consider so don’t let one of the most crucial things slip and that is to make sure you comply with the rules. That way your project will sail through building regs and get signed off when it’s completed and you won’t be getting a knock on the door from the planning department!

Your Skill Level

You are undertaking a great project and the satisfaction you will feel when it is finished is priceless but don’t over stress yourself. Don’t take on any element that you are not comfortable with, let a professional do it for you and project manage that or those elements.

Self build extension kits approach as discussed in this article provides a great starting point for homeowners looking to add an extra room or two. However, timber frame extensions using a modern approach with inbuilt highly efficient insulation that can be tailored to the individual needs and requirements of any project is a perfect way to go. We have a comprehensive guide you can read by clicking the following link covering the essentials of extension building

What to Sub Out

In essence, a build flow will be similar to the following.

Build Element	Comments
Design	Draw up your ideas into a sketch, but let someone who knows what they are doing design the building for you. They will have knowledge about what is possible and what is feasible.
Drawings	You may need some drawings for planning applications but you will definitely need some drawings for the build and the base plan.
Foundations	Foundations need to be done to building regulations, we recommend letting a professional builder / groundworker do the foundations. They will know what needs to be done and work alongside your building control inspector to ensure they are correct. Foundations are one element that are unknown until you start digging, so make sure you have a little wiggle room in your budget for the foundation stage.
Walls	Using SIP panels this is a relatively simple phase of the build. Some basic carpentry techniques and the ability to measure and cut timber accurately backed up with some guidance should help the process flow quite easily.
Roof	Again using SIP panels this is also a relatively simple phase.
Doors and Windows	You may consider getting in a professional to install any windows and doors but if you are able to follow some straight forward guidance this could be done by you.
External Finishes	Cladding is the most popular choice for the external finish of a SIP panel extension however you could have an outer brick skin or a brick plinth built. Brickwork skins are built after the structure is built.
Electrical	Your extension may need a part P certificate so it is best if not safer to have a professional electrician do the work for you.
Plumbing	If you are able, plumbing works can be undertaken and it’s an ideal time to consider underfloor heating if your current central heating system can cope with the additional load.
Plastering / Internal Finishes	This is one for the professionals, after all your work don’t let a poorly plastered space ruin your great work. A good plasterer will make sure your space looks the best it can. Don’t want to have it plastered? You can choose to have the wall clad with a variety of internal wall finishes.
Floor Screeding	As with plastering, floor screeding is a specialism and best left to the professionals but if you are confident it is something you could take on especially if a self leveling compound is needed before your finished floor is laid. NOTE don’t forget to allow your screed to dry out thoroughly before laying your floor.
Decorating	This is when you crown your masterpiece in all its glory and something most people can do very satisfactorily.

There is plenty you can do yourself and there is plenty to sub contract, decide what you want to take on remembering the specialists will be needed to comply with building regs and some elements will make your building look better than you can possibly do.

Building Your Own Extension: Conclusion

So the answer to the question can I build my own extension? Is yes you can, you could go out and collect the materials needed and build your extension.

We can help take away a lot of the stress and confusion by supplying a full kit so that you have everything you need to build your project. Plus our kits come fully designed, drawn, structural engineer checked and are delivered throughout the UK

A SipSet kit is complete, just add foundations, electrics, and internal finishes and you can build your own extension! Click a “request a quote” button and let’s start talking.