Can I Build a House in My Garden? UK Planning & Development Guide

If you have a large garden, land at the side of your house or an unusually large residential plot, you may have wondered: can I build another house on my land?

The answer could be yes. What you currently think of as an oversized garden could potentially be a garden building plot — and, for someone interested in property development, it could even become your first development project.

But owning the land doesn't automatically give you the right to build on it. Before spending money on architects or a planning application, you need to establish whether there is a realistic development opportunity and whether the numbers make sense.

Can I build a house at the bottom of my garden?

Building a house at the bottom of a large garden is often described as backland development. A new separate dwelling will normally require planning permission, and the local planning authority will consider much more than whether there is physically enough room to fit a house on the land.

Issues can include access, the relationship with neighbouring houses, overlooking and privacy, the character of the surrounding area, parking, trees, drainage, retained garden space and whether the proposal would result in a cramped or overdeveloped site.

A large garden therefore doesn't automatically equal a building plot. But neither should you assume development isn't possible simply because nobody has previously built there. The starting point is to assess the opportunity properly.

Can I build a house at the side of my house?

A large side garden can sometimes offer an excellent infill development opportunity. In some respects a side plot can be more straightforward than building behind an existing house because it may already have direct access to the road.

We still need to consider the proposed house's relationship with neighbouring properties, access, parking, the street scene, trees, drainage, services and the amount of usable garden remaining with your existing home.

If neighbouring properties have already been developed in a similar way, that planning history can be useful when assessing the potential, although another approval is never guaranteed.

Do I need planning permission to build a house in my garden?

For a new independent dwelling, you should expect to need planning permission to build a house in your garden. Don't confuse a new dwelling with a garden room, garage or domestic outbuilding.

If your intention is to create a separate home, approach it as a proper garden development and planning project from the outset.

Is my garden suitable as a building plot?

Before commissioning detailed drawings, I would want to look at the fundamentals. Can suitable access be provided? Is the plot large enough for a sensible house and usable outside space? How will it relate to neighbours? Could overlooking be a problem? Are there significant trees? Where will cars park? Can drainage and utilities be provided? Are there title restrictions or covenants to investigate? And what does local planning policy say?

Most importantly: what could realistically be built rather than what would you ideally like to build?

There is little point designing a large house and basing the financial appraisal around it if the planning authority is only likely to accept something considerably smaller.

Should I use a planning pre-application?

Depending on the site, a planning pre-application can be worth considering before committing to the cost of a full planning application.

A pre-app can help identify how the local authority views the principle of development and the important planning issues. It isn't planning permission and encouraging feedback doesn't guarantee that a later application will be approved, but used properly it can form part of your early due diligence.

How much could my garden be worth as a building plot?

This is where things become particularly interesting for homeowners. Land that has value mainly as additional garden may potentially become much more valuable if a viable planning permission is obtained for a new house.

But don't assume that planning permission automatically makes a plot worth a particular amount. A developer will normally work backwards from the expected value of the completed property, allowing for construction costs, professional fees, finance, abnormal costs, contingency, sales costs and the profit required for taking the development risk.

That's why a proper development appraisal matters before deciding whether to sell your garden or develop it yourself.

Should I get planning permission before selling my garden?

If you sell part of your garden without planning permission, the buyer is taking the planning risk and is likely to reflect that uncertainty in the price they are prepared to pay.

If you obtain planning permission yourself, you may have removed a substantial element of that risk and demonstrated what can be built. That can make a viable garden building plot more attractive to developers and other purchasers.

However, obtaining planning involves cost and there is no guarantee of success. The right planning strategy depends on the individual site.

Should I sell my garden to a developer or develop it myself?

Once planning permission has been obtained, you have another decision: sell the building plot to a developer — or become the developer yourself?

Selling a consented plot can allow you to realise its value without taking construction risk. But the developer who buys it will build the property and, if the development is successful, retain the development profit.

So before selling, I think it's worth asking: could I do this myself?

For someone who has never developed property before, that can initially sound daunting. But you have one significant advantage over many first-time developers: you already own the land.

Building on land you already own

Many aspiring property developers spend months trying to find their first site. You may already be looking at yours through the kitchen window.

That doesn't mean you should automatically build it yourself. We need to establish whether the planning prospects, costs, finished value and potential return justify taking the project on. But it's worth doing that exercise before selling the opportunity to somebody else.

For a wider look at planning risk and land acquisition, see my guide to buying land with or without planning permission.

How do I legally split my garden into a separate building plot?

Planning permission and legal ownership are separate matters. Your house and garden may currently be registered at HM Land Registry under one title. You don't necessarily have to create a separate registered title before applying for planning permission.

If you later sell part of the garden, your solicitor or conveyancer can deal with the transfer of part of the registered title, with a plan identifying exactly what land is being transferred.

The legal arrangements also need to consider rights of access, drainage, utilities, boundaries and any rights that either the existing house or new plot will need over the other land. This is an area where your solicitor should be involved at the appropriate stage.

What if I have a mortgage on my house?

This is particularly important. If your house is mortgaged, don't assume you can simply separate and sell part of the garden without involving your mortgage lender.

Your lender's mortgage may be secured against the house and the land you're proposing to turn into a building plot. Removing part of that land can affect the value of the property remaining as their security, so the lender's consent may be required before part of the land can be released and transferred.

What about access, drainage and services?

A new house needs practical access and connections to services such as water, electricity and drainage. If pipes, cables or access routes need to cross land belonging to your existing house, appropriate legal rights may need to be created when the land is separated.

The same applies in reverse if services to the original house pass through the new building plot. Thinking about these matters early can avoid expensive problems later.

What if I decide to develop the garden myself?

This is where my mentoring can continue beyond simply obtaining planning permission. I can mentor you through assessing the initial opportunity and pursuing planning, helping you understand the process and the advice you're receiving from the professional team.

Once permission is obtained, we can look at the development appraisal and establish a realistic budget before construction begins.

Finding the right builder or contractor

Choosing a contractor isn't simply a matter of accepting the cheapest quotation. I can help you understand what contractors are quoting for, compare quotations and identify what has — and sometimes more importantly hasn't — been included.

We can consider how the work should be structured, what information the contractor needs and how you monitor costs and progress as the build develops. You can also read my guide to managing a property development, builder, budget and programme.

Do I need a new-build warranty?

If you're constructing a new house that may ultimately be sold or mortgaged, an appropriate new-build warranty can be extremely important. The warranty provider will normally need to become involved during construction, with inspections and documentation required at different stages.

It isn't something I'd leave until the house is finished. I can help you understand the warranty options and when you need to start the process so it forms part of the development plan from the beginning.

How can a property development mentor help?

If you've never developed a property before, you don't have to work all of this out alone.

I can mentor you from the initial question — “Can I build a house in my garden?” — through assessing the site, planning strategy and development appraisal.

If you decide to proceed, I can continue mentoring you through the planning process, selecting the professional team, finding a contractor, understanding quotations, dealing with issues during construction and obtaining the appropriate new-build warranty.

There will be stages where you need specialist professional advice from architects, planning consultants, solicitors, engineers, mortgage lenders, warranty providers and others. Part of my role is helping you understand who you need, when you need them and the questions you should be asking.