Vital Considerations When Extending Your Home

Extending your home is a popular way to increase much needed space and add value to your property. Moving house is a costly process; from legal fees to stamp duty. There are pros and cons to each and costs can quickly add up whatever you decide to do. Our guide will help you decide if extending or moving to a new house is the best option for you.

Where to start?

Whatever type of extension you require, there is much to consider as you embark on a project to expand your home. What follows are a series of pointers on major issues, from planning rules, building regulations, through to handling the neighbours and finding a builder.

Before you start

Will your plans add value?

As with any big home improvement project, it’s worth cost-checking your plans before you begin. It is worth speaking to a local estate agent who can give their view on whether an extension would add value to your home. They should also be able to give you an indication of how much it would increase the value by, which may help assess your budget for the project.

Permitted development and planning permission

Some building works do not require planning permission These are referred to as your “permitted development rights”. Under these rules, a rear wall of a detached home can be extended by 8m to the rear if it is a single storey property, and 3m if it is double storey. This is reduced to 6m in a semi or terraced house.

There are also height restrictions: a single storey extension must not be higher than 4m in height to the ridge and the eaves, and ridge heights of any extension must not be any higher than the existing property. Double storey extensions must not be closer than 7m to the rear boundary.
There are other conditions that must be met; for example, if the extension is more than half the area of land around the original house, you will need planning permission. Extensions must be built with similar materials to the existing property.

Different planning rules may also apply if your home is in a Conservation Area. For any renovations to a Listed Property you will need to obtain listed building consent. See our listed property section.

Building regulations

Whether or not planning permission is required, any renovation project must comply with building regulations. You will need to ensure whoever carries out the work can either self-certify the work they do (eg; FENSA accredited window fitters, Gas Safe registered gas engineers, NICEIC registered electricians and so on) or will liaise with the local Building Control Officers at your council to have their work certified.

If the requirements aren’t met, you could be served with a notice to take the extension down and will have trouble when it comes to selling your home without the relevant Building Regulations certificates.

Insurance provider

Before starting the project it’s important that you contact inform your home and contents insurance provider of your plans. The extension will likely increase the rebuild cost of your house which insurers take into account when pricing premiums. Any building work could put the property at risk of damage.

If you don’t let your insurer know you are extending and there becomes a problem with the property, you may find your policy is void. Your insurer will let you know if your current policy will cover the new extension. Your premiums may increase.

You should also check that any builder working on your property has indemnity insurance to cover the costs should something go wrong.


If you own the leasehold – rather than freehold – to your property, you should check the details to ensure you have the right to make alterations, usually subject to approval from the freeholder. Do this sooner rather than later as there may be additional costs involved to obtain their approval.


Building projects are sometimes a major cause of disputes between neighbours. If planning permission is required, your neighbours will be consulted by the local planning authority. It might be good idea to let them know about your plans well in advance, particularly if the works may cause disruption.

Party Wall Act

A party wall is the shared wall dividing the homes of two separate owners. It includes garden walls built over a boundary and excavations close to a neighbour’s property (within three or six meters, depending on the depth of the new foundations).

Party Wall Agreements between neighbours are most commonly needed for loft conversions and extensions, damp proofing and/or digging of new foundations.


Finding an architect

Depending on the scale of the project, you may wish to involve an architect. You don’t have to, even for large renovations and builds, but it might be easier to have a professional draw up plans. Using an architect will generally mean you’ll get a far better end result, however their fees are usually around 15%.

Obtaining structural engineer calculations

A structural engineer can also provide technical drawings and calculations which can be used to seek Building Regulation approval and will then be used by your building contractor and/or architect during the renovation work.

Choosing a builder

How to compare tradesmen

Professional, reliable tradespeople can be the make or break of a successful building project. Online reviews are a good place to start when comparing builders and other contractors, as is word of mouth.


Getting quotes

Shop around. We’d always recommend getting at least three quotes from three different contractors for the work. You might need to ask at least five firms to get the best quote.

Setting a budget

Make a list of everything you would like included. Compare your quotes item by item and when pricing services and materials always check the VAT is included in the costs.

We’d also recommend setting aside around 10% of the total cost for unexpected additional costs.

You will also need to work out the best way of funding the cost of your home improvement project.

Building an extension to your home isn’t a decision to take lightly, and should be carefully considered. Once you have thought everything through you may decide it is not right for you and that moving is a better option. If you decide to move we are able to help you source competitive quotes for conveyancing solicitors with Conveyancing Supermarket’s online calculator.