Can I self build a house in my back garden?

15 February 2022
by Dwight Cain


I'd like some advice on how to resolve an issue I might have with a property that I want to buy. The property is currently used as a HMO and it has a large garden. A planning consultant has suggested that the land would easily accommodate a self build.

We are going to purchase the property using a HMO mortgage and would like to get planning permission for the self build once we've concluded on the sale. Assuming we get planning permission, I'd like to build another property in the back garden, sell it, and retain the existing HMO (with its reduced parcel of land). Unfortunately I can see a number of problems going forward that I would need to overcome in order to do this.

1. I'm assuming that I would need to legally carve off the parcel of land that I intend to build on in order to sell it. Assuming this is correct, I'd expect the mortgage company (that I used to purchase the property in the first place) would have the right to say no to this, as this would naturally reduce the value of the remaining property (and its reduced parcel of land). Is this correct and if so, do you have any suggestions how this could be overcome with the mortgage company?

2. If I were to live in the self build property myself, would I need to legally carve off the land at all? I assume the mortgage company would effectively own the new self build property as well as the existing HMO, but this wouldn't necessarily be a problem whilst I lived there - it would only be a problem if I decided to sell it on as a separate property from the HMO. Is this correct?

3. If I were to live in the self build, it would need its own address. Would I be able to get a new address for the house if it wasn't legally separate (separate title deeds) from the existing HMO property?

4. Paying for utilities - would I be able to have separate utility bills from the HMO property if its wasn't legally separate? Or do separate utility bills only rely on a separate address?

5. Do you know any specialist solicitors/conveyancing firms who have experience of dealing with this kind of thing?

Any advice would be greatly appreciated.

2 Answers

  1. Anamika Talwaria says:

    Hello Dwight,

    Thank you for your question. I’ve posed this to our experts and hope to have an answer for you soon. It’s quite an in-depth one though, so do bear with us!

    Anamika Talwaria, Build It Features Editor

  2. Martin Gaine says:

    Hello Dwight,

    Firstly, these are quite specific legal and mortgage questions, so perhaps another colleague can advise, but from a planning perspective:

    Building a separate dwelling in a large garden is a great way to boost the value of your property. The first step is to apply for planning permission – if you are not successful you (unfortunately) won’t have to grapple with creating a separate legal title for the new property.

    If planning permission is granted and you choose to build, you may need to get your lender’s permission – their existing legal charge covers the whole site and there may be a requirement in your mortgage T&Cs that they be made aware of any significant works.

    If you want to keep the completed building for yourself, there is no requirement to create a separate legal title. But if you wish to sell the plot or new build to a third party, a separate title would need to be created and this would, of course, need the lender’s approval. They may be willing to grant permission if the value of what remains has not fallen substantially and the loan-to-value (LTV) is unchanged. They may require that you move onto another product, or you could choose to refinance the HMO (on its smaller site) to a new lender altogether.

    You can get a new address for the new build even if there is not a separate title – just apply to your local council’s naming and numbering team. You can also register for council tax and get independent utilities connected.

    Martin Gaine (Build It Planning Expert)

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