It is a common problem – your home simply isn’t big enough anymore. Maybe the kids have grown up and wanted their own rooms or a new arrival is on the way. Perhaps an older family member is coming to stay, or you need space for a home office. Whatever the reason, adding an extension to the house is a perfect way to create much-needed space. But where do you start with adding a home extension?
Why extend rather than move?
It is a personal choice whether you want to move to a new, bigger house or extend your existing one. But there is a strong case for the benefits of extending. For starters, it is simpler – moving home is never a simple and fun process!Moving to a new house also incurs all kinds of fees such as estate agents, legal fees and stamp duty that all add up. For the money you spend on all of this, you can practically pay for the new extension! And you already know your home, the area, the facilities so there’s less upheaval.

Extension considerations
Extension considerations
There are a few things to consider when looking at an extension. One that some people use to help plan the project is the potential investment and return on it from adding the extension. If you plan to sell the house at some point, how much will the extension add to the value? Sometimes it may not be economical to add one or it might be better to go with certain styles. If you plan a single storey, it might be worth looking at a double storey instead of just a single storey as the cost often isn’t that much more.
Then there are the practical considerations which you will often need help with that don’t relate directly to the actual structure. Can workmen get equipment and materials near to the house? Where will stuff be stored while the construction is taking place? If you don’t have off-street parking, this can lead to planning permission problems.
The technical considerations can include things like:
- Conditions of the soil
- Services in place
- Trees surrounding the area
- Flooding history of the property
- Any right of way considerations
You definitely want to check these issues before even starting to plan as they can cause major issues down the line.

Extension Costs
Extension Costs
The cost of the extension depends on a number of variables from the location to the type of extension, the size and construction materials. However, there are some rough guidelines to help with your decision. For a single storey extension, a cost per square metre could be £1000-1680 for basic quality, up to £1920 for good quality and up to £2160 for excellent quality. The time duration of the build can vary.
Two storey extensions tend to cost not much more per square metre because the most expensive stuff is only done once from the foundation to the roof.
Planning permission
Planning permission
The biggest question for any project is whether planning permission is needed. For most types of extension, the answer to this is no but there are some conditions. The process is called Permitted Development and under it, you can add an extension under the following conditions:
- You can add to a detached house by 8 metres to the rear for a single storey or 3 metres for a double storey
- A single storey can’t be higher than 4 metres at the ridge or higher than the existing property
- Two storey extensions have to be more than 7 metres from the rear boundary
- Extensions can’t be forward of the front wall of the house
- Extensions should be the same or similar in materials to the house
- Side extensions can’t be higher than four metres and no more than half the width of the house
- Extensions can’t cover more than 50% of the total garden space
There are additional rules and exceptions for properties such as Listing Buildings and those in conservation areas, so it is always worth checking with your local planning department to make sure nothing else applies.
And no matter what, you will always need to remember building regulations when adding an extension – they can also help with this. These look at minimum design and construction standards laid out by the government and apply to every property in the UK – and extensions to them.