What you need to know before building an extension

If you’ve outgrown your house, building an extension is a great way to add extra space without having to move. To help with your planning, we take you through the different types of extension, planning and design considerations, plus tips for living in a building site.

Types of extensions

  • Loft – Using the space in your roof is a straightforward option – but you’ll need to check how much space your roof structure allows for. You’ll need to consider things like the amount of standing room in your loft, where you’d put windows and stairs, and where would you relocate the water tank to. If your current loft isn’t overly spacious or the roof pitch is too steep, you may want to go for a dormer loft or change the roof structure – these will be more expensive options but will give you increased living space.
  • Garage – A great way to add more downstairs living space or a spare bedroom, although you should think about the shape of your garage and how you’ll use the space. Most garages are long and thin, so it makes sense to split the space in two – a bedroom with a shower room, or playroom and an office, are good combinations. Make sure that you get the space properly insulated and ventilated – and consider leaving a small section as garage space to store essential items.
  • Single or double storey extension – Probably the most complicated option as you’re adding to the footprint of your house and, depending on the size, you may need full planning permission. You’ll also need to plan the flow of new rooms with the old layout, to give you a space which really works for your family. If budget allows, it’s a good idea to think long-term with this type of extension – if you may need more bedroom space in a few years, it’ll probably be more cost effective to go straight for a double storey extension.


There are 2 types of planning:

  • Permitted Development – Applies to work which doesn’t need a planning application. The type of property you live in, planned size of the extension, and whether you live in a designated area, will affect what you’re able to do under permitted development.
  • Full planning permission – If your plans don’t fall into permitted development, you’ll need to submit a planning application, and it’s worth getting the help of an architect or structural engineer, so that your designs and drawings meet the necessary planning and building regulations.

Living in a building site

Once your building starts, it’s likely that you’ll be living with disruption for a while, so try to plan ahead as much as possible.

What to expect:

  • It might be cold if your build happens during winter.
  • Your water might be off if your tank is relocated.
  • If your bathroom or kitchen are out of action you won’t be able to wash or cook.
  • If your house looks like a building site, think about the safety of small children and pets.


  • Move out for a while – to friends or family or even an onsite caravan.
  • Coincide the major disruption with a holiday.
  • Keep one room clean, tidy and free from work as a retreat from the chaos.
  • Join a gym so you can use the shower.

Don’t forget to tell your insurers

Before committing to any work , be sure to understand whether your home insurance will cover your plans - as there's likely to be restrictions to the type of work that will be covered, or you may need to get specialist insurance in place. Don't forget once you've completed the project to adjust your contents sums insured or number of bedrooms if you've increased in size.


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