Building an extension checklist - avoid these pitfalls

Are you planning on building a house extension in the UK? Take it from us, it can be an exciting and chaotic time in equal measure! You’re adding heaps of space to the footprint of your property, but the build itself is complex to plan and there is a lot at stake to say the least. Jumping head first into a building or renovation project like an extension, can land you in a sea of costly mistakes and stress if you’re underprepared.

But fear not intrepid renovator! We’ve written this guide and produced a very useful checklist to guide you through the pitfalls to avoid and the tasks you need to complete when building a house extension. Being organised is key to the success of your extension, so keep reading:

Your Building an Extension Checklist
+ bonus free spreadsheet download

Stage one - House extension brief and budget

Establishing your brief and budget is covered extensively right here on the Fifi McGee website and within our courses but in summary, establishing the size of your project, key rooms and finishes will help in planning the next stages.

When planning your budget, you can calculate a rough budget for a house extension using a cost per metres squared of £2000.

Whether you need an architect or take a different route to construction design will be down to your own preferences and your site. It’s possible to draw planning permission drawings yourself for simple sites – but we don’t recommend it unless you have experience. Ensure your budgets are factoring in professional services, planning fees and contingency.

Stage two - Planning permission

With your budget, brief and consultants in place, you can now look towards a layout and design for your house extension and moving towards gaining planning permission.

This stage will involve the appointment of any professionals to conduct this work for you unless you are choosing to conduct the work and submit the planning application yourself but usually this task sits with your team.

Once you have a design, layout and drawings you are happy with, you’re ready to submit your project for a planning application. Householder planning applications normally take about 6 weeks – but this can vary wildly depending on location. Your plans will be subject to certain rules.

Stage three - Building regulations

With approval granted for your house extension, you can now move onto covering building regulations standards within the design. It is recommended that a professional covers this information for you on your design drawings.

In addition to this you will require two other consultants, a structural engineer will cover building regulations Part A and to make sure the building is structurally sound. A building control officer, either from the local authority or an ‘approved’ private inspector will check your project meets building regulations requirements.

Other items should be checked at this stage and will be different for each property. Build over agreements may be required if your new extension crossed a public sewer and party wall agreements will need to be secured if you are building near a neighbouring boundary. Other items may also be required, such as planning condition discharge applications for complex sites and projects.

In summary, it is important to cover all possible bases prior to construction starting in order to avoid issues.

Stage four - Finding a builder

At this stage you should be ready to find a builder – but be sure to carry out due diligence. Seeking quotations and checking agreements is important at this stage prior to starting on site with your chosen builder.

It’s also an important time to consider what work will be done by whom and considering the possibility of DIY for certain items in your house extension. This is something our building extension checklist will help you streamline.

Again, checking building contracts and quotations can be a specialist area, seeking professional help at this stage can be helpful to make sure you are entering into a legitimate agreement with a trustworthy builder. It can also help to ask other UK renovators for their experiences and get a temperature check on costs in your area.

Stage five - construction

With the builder at work and an agreement in place, there shouldn’t be much else that requires your direct input (aside from a mountain of design decisions 🤯), particularly if you have a professional conducting contract administration.

Despite this, it’s still worth checking on progress, building control officer visits and that standard procedures in your construction contract agreement are being carried out.

After practical completion has been achieved on your project, it’s important to take note of any issues you have with your new extension within the defects period, this is normally 6 month to 1 year period in which the builder will be on call to fix minor issues with the project.

Start your extension planning with FREE ACCESS to an EASY extension checklist

You’re probably thinking there’s a heck of a lot here to take to the next stage, remember and track. You’ve got a lot on your plate and you definitely don’t want to be missing important steps that could get you in a pickle later down the line.

That’s why we’ve created this simple extension checklist which breaks down the house extension process into easy steps. Tick off items in each stage before moving onto the next stage, this way you will be progressing having covered all the important bases.