A guide to home extensions

If you’ve outgrown your house but don’t want to move, then building an extension could be a great way to add the extra space you are looking for. To help you decide if this is right for you, read on to find out more about different types of extension, planning and design considerations, what you need to tell your insurer plus tips for living through the build in our guide.

Before going ahead, consider the ceiling value

Estate Agents use the term ‘ceiling value’ to refer to the fact that properties often have a maximum amount that they’ll likely sell for, no matter what modifications are made. Often this relates to the area that houses are in and is also known as ‘outgrowing your street’.  In simple terms look at the average house price on your street. If you’re planning an extension and hoping to eventually sell at well over this average, you may want to reconsider as it’s unlikely the work will add that much value to the property.


If you’ve decided to go ahead there are two main types of planning that you would need to research before you start any build. It’s always best to get advice from an architect or your local planning authority for guidance on what’s needed.

1. Permitted development

This applies to work that doesn’t need a planning application. The type of property you live in, the planned size of the extension, and whether you live in a designated area will affect what you’re able to do under permitted development. Even if a full planning application isn’t necessary, you will need to ensure your plans will meet building regulations as an inspection and sign-off from Building Control may be required on completion. Your builder should be able to advise.

2. Full planning permission

If your plans don’t fall into permitted development, you’ll need to submit a planning application. 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.

3. Other types of planning permission

There are other types of planning consent that you may need to take into consideration, which are:

  • Household planning consent
  • Outline planning consent
  • Reserved Matters
  • Listed building consent
  • Advertisement consent
  • Lawful development certificate
  • Prior approval
  • Removal/variation of conditions
  • Approval of conditions
  • Consent under tree preservation orders
  • Non-material amendment of an existing planning permission

As well as the above, if your property is in an Area of Outstanding Natural Beauty, you’ll have further restrictions around home improvements. You can check this by contacting your local planning authority.
For further information on planning types follow this link

Types of extensions

1. Loft conversion

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 things such as the water tank. You will also lose storage space if your loft is currently used for this. 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.

2. Garage conversion

This can be a great way to add more downstairs living space or a spare bedroom. Think about the shape of your garage and how you’ll use the space. Most garages are long and thin, so it can make sense to split the space in two, such as having a bedroom with a shower room, or playroom and an office. Make sure that you get the space properly insulated and ventilated. You could also consider leaving a small section as garage space to store essential items if you’re used to the storage space.

3. Building onto the existing footprint of the property

This is probably the most complicated option 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. You should also consider how the property looks from the outside – you’ll want to try and make the extension complement the original build if you can. Undecided on what size of extension to go for? It’s a good idea to think long-term. For example if you think you may need more bedroom space in a few years and budget allows, it’ll probably be more cost effective to go straight for a double storey extension.

4. Side Extension

Older properties such as those from the Victorian or Georgian era may have a side alleyway which is rarely used and could make for an excellent opportunity to improve the width of your home.
This isn’t exclusive to this style of property and could be completed on any property with side access. This could be a single or double extension, depending on what you choose to do full planning may be required. Please bear in mind that older properties may be listed. If so, they will have more specific restrictions around what can and can’t be changed.

5. Sunrooms

By adding a sunroom to your property you are going to have a space which is filled with natural light. Although similar to a conservatory, a sunroom is built as an extension so it has a full roof, can be connected to the central heating and allows it to be a functional space all year round.

Build considerations

There are many considerations to make sure your home improvement project goes to plan. We’ve jotted down some of the crucial ones:

1. Use a qualified builder

A trusted recommendation speaks volumes when it comes to this kind of work. Make sure you get a number of quotes, see examples of previous work and get references from existing clients. Also, consider how you get on with your chosen builder as they will be in your house for weeks if not months. Are they going to be sympathetic to the needs of your family while the works are carried out?

2. Through rooms may or may not work for you

By a through room we mean rooms that can only be accessed by going through another. Of course, this might work if you’re creating a bedroom and ensuite, but if for example you’re creating two new bedrooms you’re unlikely to want to walk through one to reach the next.

3. Use the right materials

This doesn’t mean you have to stick to what your house is currently made from – there are numerous examples of contrasting materials being used in extensions that can complement the original build. If you are unsure get professional advice before submitting plans

4. Don’t forget your budget

As well as your initial budget for the build, it’s a very good idea to have a contingency amount in place, should things not go to plan.

Living through the build

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

What to expect:

  • It might be cold, particularly if your build happens during winter and especially if your roof is removed for a loft extension.
  • Your water might be off for a period of time if your tank gets relocated.
  • ​​​​If your bathroom or kitchen are out of action it will be harder to wash or cook, so you’ll need alternative plans.
  • If your house becomes a building site, think about the safety of the whole family including your pets.


  • Could you move out for a while, particularly when the project is at its most disruptive? If you’re able to stay with friends or family that could be a good option, or you could consider a short term rental. Make sure you check your home insurance as you may need to inform your insurers if doing this.
  • Coincide the major disruption with a holiday.
  • Keep one room clean, tidy and free from building work as a retreat from the chaos.
  • Craving a hot shower? Try family, friends or even the local gym.

Don’t forget to tell your insurers

Before committing to any work, be sure to understand whether your home insurance will cover your plans. There are likely to be restrictions to the type of work that will be covered, or you may need to get specialist insurance in place. You should also let them know if the property is going to be unoccupied for a period of time. Don't forget once you've completed the project to adjust your contents sum insured if you’ve bought additional furniture, and let your insurer know if the number of bedrooms have increased.

Whilst you should tell your insurers you are having work carried out it is equally important to check with your builder that they have adequate insurance in place - if something goes wrong with the building work and causes damage to your property you need peace of mind that this is covered - whilst doing this, check that the builder has liability cover in place.