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    Can You Convert Two Properties Into One?

    By The reallymoving Team Updated 28th May, 2024

    Reviewed by Em Smith

    You may have wondered whether you could purchase the house next door to yours and knock through to make one big house. What documentation would you need and how simple would the process be?

    Can You Convert Two Properties Into One?

    Written by property expert Kate Faulkner

    If you get on well with your neighbours, they may let you know before their house goes onto the market that they are looking to sell.

    Alternately, if a board goes up and you are interested in buying to either rent it out or extend your property into the one next door, there are some major considerations to think through before you go ahead.

    What to consider before you convert

    How much will it cost?

    The first thing to consider is how much will it cost? Although it sounds like a nice idea, staying in the same street, even staying in your home while the one next door is renovated and knocked through, it’s still a major renovation project that will cost a lot of money.

    No doubt there will be problems that need solving and you’ll have to manage and co-ordinate a lot of people working on two, rather than just one home.

    After considering it for some time, it might be easier to sell up and buy a bigger property that delivers the space you need.

    What planning needs to be done?

    Before you go ahead and make an offer, first check if your idea will require any planning. It could take some months to design and secure the drawings (even assuming the house next door is similar or the same as yours) that need to be submitted to planning.

    The good news is you don’t have to go the whole hog initially, you can get some basic drawings done and then visit or speak to the planners online and they will be able to give you an indication of whether it’s possible or not. Sometimes you might be surprised and get a quick yes, other times you might get an unexpected no and have to reconsider your plans.

    From a cost perspective, there are companies that will create initial estimates for you to work from. Some of these are free such as Homebuilding & Renovating’s Build Cost Calculator or you can visit places such as the National Self Build and Renovation Centre. On their event weekends they will often have experts who can help you cost your project on the day, as well as give you access to lots of useful building essentials, from windows to doors and even a house that shows you the different stages of a renovation.

    Alternatively, your architect or technician will give you a guide. Once you are confident you are going to move forward, you would check these costs with a builder, or individual tradespeople, to cost the job and give you an idea of how long it will take.

    How long will it take?

    We estimate it should take a year or more.

    Buying the property

    Buying the property is likely to take at least three months. During this time, you can have your designs and drawings created.

    Planning and renovations

    Planning will then take some months (if required). The hardest bit is likely to be getting actual estimates and timings from builders etc. Depending on how big a job it is, it is likely to take at least three months if not a lot longer to create the home you want.

    Remember that good builders and tradespeople aren’t typically available ‘on demand’ and for big projects that could take six months or more to complete, you may have to wait a year or so before they can begin work.

    Will you need planning permission/other documentation?

    Usually, you won’t need planning permission, but it depends on what your plans are for the two properties, especially if you are extending upwards or outwards.

    Check the local policies

    It’s always best to discuss your plans with the local authority and ideally get something in writing to confirm that you can proceed. Checking in advance for any local policies can help speed up the process.

    Building control

    Whether you need planning permission or not, the main job which you will need to carry out is securing building control sign off for all the work undertaken. In England, they run from Part A through to Part R and regulations on materials and workmanship.

    The types of things they include are standards for:-

    • Safety – structure, fire, and glazing

    • Sound, ventilation, access

    • Drainage and water disposal

    • Electrics, heating, and hot water

    • Security

    Building control will require regular checks on the property from a local building control officer (which you will have to fund) and certificates will be required to confirm the work has been done to the latest standards. Hang onto these as you’ll need them if you do ever wish to sell.

    The rules can be different for each country. Planning Portal is a useful (and essential) site for England which is also helpful for planning permission.

    Pros and cons of buying and knocking through next door

    There are lots of reasons to buy your neighbours home, but also some things to consider that might put you off.

    Here’s a list of pros and cons to have a think about and chat through with your experts to see how they can mitigate them for you.

    The pros

    • For some, it’s purely that they would like to ‘stay put’. It might be the current home is one you have lived in for a long time, and you love the area and your neighbours, but it’s too small for what your current family needs.

    • Another reason is that to renovate a big house or build one from scratch can be a major task and take years. Buying the home next door and knocking the two together can be quicker and potentially cost less.

    • If it’s a semi-detached, you will switch your property to a detached home and historically, in many areas these will command a higher price and good capital growth. If it’s a terrace, you will share less walls with your neighbours!

    • Potentially pay less stamp duty as you already own your current home and pay stamp duty at a lower value.

    The cons

    • You may need planning permission and, depending on the dynamics of house prices in the area it may be cheaper to buy a bigger home. Buying two and knocking them together could be worth less as one property.

    • The layout of the properties may not lend themselves to being knocked through. For example, can the entrance and hallway be knocked through together or will you have to substantially change the layout of the building (which may increase the cost)?

    • The renovation work could take a year or more, rather than moving into another home which doesn’t take quite so much time.

    • You may have increased costs for some time until you create one home. For example, two sets of council taxes, electrics, water etc.

    Other things to consider

    It’s certainly not impossible to knock two properties together and may be your dream solution, but as ever with buying a home and a major renovation, things that you might not expect can make life a little bit more difficult than you’d first think:

    Could it be converted back to two homes

    One thing to consider, especially if you have children, is whether you always want the property to be one?

    If you have kids, would you want them to be able to convert the property back into two or maybe give this option to future owners?

    If you want to keep this as an option, you will need to bear this in mind when you are making any changes to the layout of the property.


    It’s worth chatting to a broker if you need to borrow money to fund the purchase and renovation – and even if you have cash, you need to make sure the work you do will be acceptable to a lender in the future.


    Check what legal paperwork you will need to covert to one property. Could it be easy to legally transfer it back into two properties later?

    Converting two properties into one FAQs

    How will the numbering work on the converted property?

    This might seem a simple thing to sort, but remember, every service, company etc will have both of your addresses on their books.

    For anyone that’s changed their address when moving, it may make things very complicated for years to come!

    The new combined property will take one of the numbers of the previously separate properties. 

    Which property is going to provide the utilities during the renovations?

    It could be both or you could choose one property and shut them off in the other – but do talk to your architect/contractors to see which is best.

    You will also have to work out how/if to integrate the heating systems.

    Can I convert my house into flats without planning permission?

    In November 2023, it was announced that the government is planning to remove the requirement for planning permission when splitting a house into two flats. The Permitted Development Right convert one house into two flats should be implemented some time in 2024.

    However, for splitting into more than two properties you will still need to get planning permission.

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