How to plan an extension to your home

How to plan an extension to your home

How to plan an extension to your home.

Hello there, it is Hayley here! Welcome the third in our “How to” series of blog posts. Writing this comes from years of experience of managing projects like this through our estate agency business. If you doubt my credentials, I can tell you I have won awards for Property Renovation.


In this article, I shall be looking at how to plan an extension to your home and the complications that can occur when your renovation turns into something more complex. Planning kitchens and bathrooms is one thing, but single and double storey extensions all have regulations that you may need to adhere to.


If your plan is to extend your home, you might need a structural engineer. In my experience, these are the projects you leave to the professionals.



To begin with, I have to stress you must do your research. Talk to your local Estate Agent and find out what other extension types they have seen, when selling property in your area.


Ask what sells well? What would generate a decent return? Also, ask for their general input. It’s human nature to just go ahead and order whatever it is you want. But unless your pockets are deep, every decision should be measured appropriately.



Budget is the governing factor in any decision you make. Budget wisely and keep an eye on your costs. We’ve got a great spreadsheet you can download to help keep track of your costs. 


Take into consideration that not all of your budget will not be spent on the build and materials. You may have to hire an architect to draw up the plans. You would be wise to hire a project manager so that you don’t have to handle the stress and logistics. I would also advise getting your own self-build insurance, just in case your builder only has Public Liability and Public Indemnity insurances.


Should any claim arise, you will have to work a lot harder to prove your builder is at fault to get a payout. That will always cause you more stress and anguish should things go wrong.



I always talk about setting goals for any renovation project. This keeps you clear and focused on what you need to achieve, what end result you would like and also to grasp costs on fixtures and fittings. 

The main question is, why are you building an extension and how do you plan to use it? Is it a new living area you seek? An extra bedroom? A home office or study? Side extensions? Put this down on paper and work backwards from there!



Now you have set your goals you can get into the planning of the project. In this stage, there are a number of things you need to look at and take care of.



Your extension, whilst well planned and even passed by building regulations, can still be contested by your neighbour. Most homes are covered by “right to light” and this supersedes local planning permission. It does not mean that your extension cannot cover a neighbour’s window, but if they can prove you are restricting enough natural light for what they reasonably need, then you could face some difficulties.


Then you need to be aware of the Party Wall Act 1996. This act allows you to carry out work as far as your neighbours land and or buildings. If your extension works are within 3 metres of the party wall structure, or you dig foundations within 6 metres of the boundary, you must adhere to the Party Wall act.


In most areas, single-storey extensions do not need planning permission, but you must comply with local building regulations and get approval from your local council or parish. Were you aware that replacement windows, underpinning and rewiring are covered under building regulations?


All new building work including sheds, some conservatories or orangeries and most alterations must comply with building regulations to have permitted development.


Works Needing Approval:


1) Home extensions – kitchen, bedroom, lounge, etc.


2) Loft conversions. Internal structural alterations, for example, the removal of a load-bearing wall.


3) Installation of baths, showers, WCs which involve new drainage or waste plumbing.


4) Installation of new heating appliances or systems.


5) New chimneys or flues.


6) Altered openings or positions for new windows.



You might not know this but if your home or property is located in a conservation area, you will suffer from restricted development rights. That means extensions or renovations that do not require permission are restricted. Loft conversions will almost always require planning permission from local authority in these areas.


Architects are almost always required to get your project off of the ground. They will need to know which are load-bearing walls and do the calculations for the steel beams these projects often need. They can usually file any associated planning permission paperwork that your project requires. Find a local architect that specialises in your particular extension and maximise the opportunity for your new space.


You will also need a construction brief. This document is an in-depth breakdown of what your extension project will entail. Knowing how to plan an extension to your home is one thing, but writing this document is a step beyond. You will most certainly want to work with your architect or project manager on this, as they will have the experience needed to ensure this covers everything you need it to.




I know I touched on this earlier, but insurance is a peace of mind. Make sure that your builder has a current cover and ask to see a copy of their certificate, don’t just take their word for it.


Also, make sure your project manager has the appropriate professional insurances in place. If something goes wrong, either your builder or project manager could be liable. You wouldn’t want something drastic to go wrong and find out that you have to foot the bill because you didn’t do your due diligence.


Most self-build policies work on the basis of a single premium. For new builds, this is based on the rebuilding costs on a sliding scale, and for a home of around 140m² the average cost will be between £600 and £1,200, with the variation accounted for by the proposed construction costs.


Cover yourself to ensure your project gets finished. Should your builder, unfortunately, become ill or just disappear (or even your project manager for that matter) your insurance can cover you for the cost to replace either one and continue the plan’s application.


Types of extension

The common types of extension to your home are the:

  • Loft Conversion
  • Basement
  • Single Storey extension
  • Double Storey extension


If you stick to the information I have listed above, you won’t go far wrong. Always work with the professionals, don’t try and cut corners. I’m sure you’ve seen cowboy builders with Dom before.


Each type of extension will have its own set of rules, requirements and plans. If you want to find out more about your basement conversion check out


Tips to leave you with

Whilst some councils will have their own regulations, most are working to similar guidelines. Where social housing or listed buildings are concerned, there are restrictions around room sizes and design, which are more relaxed in private accommodation.


And when you are planning the layout of your extension, try to avoid through rooms. Your home should have a flow to it, so rooms are accessible through hallways or landings. Unless of course, it’s a conservatory which typically attaches to the kitchen, lounge or living room.


Hopefully, you have found this article a worthwhile read and if anything it has given you time to think about how to plan an extension to your home. It isn’t extremely in depth, you’d be here for days. But I do believe I have covered the more important factors you could come across.

Mariana Woll About the author
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