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.
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.
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.