Home extensions and improvements

Many properties have potential for expansion – either up, out or even down.

As long as building works are undertaken sensibly, such work can add value to your home while giving your family more room to live and work.

With a little imagination and some expert advice, you could add a conservatory, convert your loft into the home office or spare room you’ve always wanted, or even excavate a cellar or basement.

This guide has been written by RICS. It offers advice to homeowners who are considering extending their home.

It is also useful for:

• those looking to improve their property before putting it on the market and
• homebuyers planning to take on a property with a view to developing it.

RICS expertise when extending your home

A home extension is a major project. It will probably cost thousands of pounds and cause considerable disruption. But, if carefully planned and executed, it should add value to your property and greatly enhance your living space.

To minimise problems, consider appointing an RICS member to take you through the process from start to finish and ensure that works are carried out with as few hitches as possible.

An RICS member can:

• advise on which properties have potential for expansion or improvement (if you’re thinking about moving house)
• act as your agent when dealing with the statutory authorities, since they:
  • understand planning law
  • understand compliance with building regulations and
  • have experience of historic and listed buildings.
• seek and appoint reliable building contractors and can act as project manager, managing the contract and monitoring the work on your behalf
• produce initial designs, plans and specifications for your building work. They can also provide a cost-consultancy service and can manage your budget throughout the project, to help stop overspending and
• offer advice on the best method of settling any disputes that arise (if your project runs into problems).

Extending your living space

Before starting any home-improvement project, you first need to consider:

• the size and shape of your house and garden
• how much additional space you want or need
• how much you can afford
• whether the project will add value to your property
• the aesthetics and
• whether it will impact your neighbours.

If you live in a conservation area or your home is listed, there may be additional constraints on the type of works – if any – that you can undertake.

If you can’t extend your home beyond its existing elevation/footprint, you may still be able to knock down an internal wall to create more space or even partition a room to add a bathroom or study area.

Planning permission

In England and Wales, the first thing you should do is consult the Planning Portal. This will give you an overview of how the planning system works. In Scotland and Northern Ireland, you should contact the specific local authority.

You don’t usually need planning permission for minor internal alterations, unless it’s a listed building. 

There may also be additional restrictions on permitted development rights, especially in conservation areas. Discuss your ideas with your local planning officer to see if permission is likely to be granted.

Don’t presume you’ll be granted permission just because your neighbours have a loft conversion or other development – regulations may have changed over time.

There are a variety of government resources to help you to assess whether your alterations need planning consent, depending on whether you live in:

• England
• Northern Ireland
• Scotland or
• Wales.

If planning permission is refused, there is a right of appeal. But if you go ahead without permission, you could be served an ‘enforcement notice’. This could mean being forced to demolish the work you have just had done.

If in doubt, seek specialist advice from an RICS member – it could save you considerable time and money.

Building regulations

As well as planning permission, your extension may also need building regulations approval.

Building regulations ensure that your home:

• remains structurally safe
• is protected from fire risks
• is energy efficient and
• has adequate ventilation, etc.

This is a complex area that has your health and safety at heart.

If you have any doubts about how the regulations may affect you, don’t leave it too late – consult an RICS member before you sign-off the design and appoint a builder.

• See gov.uk for the rules that govern building regulations in England.

• For rules in Scotland, see the Scottish government’s website.

• For rules in Wales, see the Welsh government’s website.

• For rules in Northern Ireland, see Building Control Northern Ireland.

There is a list of common projects on the Planning Portal which you may find helpful.

Once work has started, a building control surveyor will make a number of checks to ensure that building regulations are complied with.

It is important that you obtain a completion certificate from the building control body when the works are completed (this is also known as a final certificate if using a private approved inspector). If you don’t get one, it could cause problems if you want to sell the property, obtain insurance or get a mortgage.

All applications are different and the rules are complex, so it is well worth considering employing an RICS member to:

• draw up and submit the plans
• obtain approvals and
• oversee the project on your behalf.

Party walls

In England and Wales, the Party Wall etc. Act 1996 requires property owners to follow a specific procedure when undertaking building work that involves:

• a party wall or a party fence wall (a garden wall that straddles the boundary)
• certain excavations and foundation constructions close to neighbouring buildings and
• new walls at boundaries.

The Act permits owners to carry out certain specific works, including work to the full thickness of a party wall, while at the same time protecting the interests of anyone who might be affected by that work.

Note that the Act only applies to England and Wales and does not exist in Scotland and Northern Ireland.

Please see the Party walls consumer guide for more information and consult the service of an RICS member if required.

Cellar conversions

If you don’t have the space to extend your house upwards or outwards, consider going down.

Cellar conversions or basements are becoming increasingly popular for creating fun or practical space, such as:

• home cinemas
• games rooms
• utility rooms and
• storage areas.

You could add an extra storey with little change to the external appearance of your home.

However, cellar conversions should always be carried out by skilled professionals, especially if additional excavation is required.

Note that basement projects can be structurally complex and can cost up to three times more than a loft conversion.

Check with your local planning officer and building control body before starting excavation works. Always look at other options before considering this type of alteration.

Also see the previous party walls section for further advice.

Loft conversions

If you need more space but don’t want to lose part of your garden, extending upwards could be the answer.

More than a million homes in the UK now have loft conversions, with the market growing by an estimated 5–10% each year. Estate agents calculate that an average loft conversion costs around a third to one half of the price of moving to a property with an extra room.

Turning your attic into useable space could increase the value of your home by as much as 25%, especially if you are adding an extra bedroom and bathroom.

But there are several important points to bear in mind.

• Not every loft can be turned into living space.
• Costs will vary greatly from house to house, so seek professional advice early on.
• Remember that:
  • you may need planning permission for a loft conversion (especially if you live in a conservation area) and
  • you must comply with building regulations.
• Choose your builder carefully, and make sure they have experience in this complex area.
• Consider appointing an RICS member to oversee the works. Acting as your own project manager can be complex, time-consuming and costly if you have no previous knowledge or understanding of the construction process.

Choosing a builder

A major extension that involves structural alterations to your home should never be considered a DIY project. It should be fully designed to help builders get comparable quotes.

When choosing a builder, keep the following points in mind.

Shop around

Get at least three detailed quotes. If possible, use personal recommendations and check the quality of past projects yourself.

Ask lots of questions

• Does the builder have experience of the work you require?
• Can they confirm everything in writing, including a fixed period for completion?
• Can they show you their health and safety policy and insurances?
• Can they provide references from other clients? (Take your time to follow these up)
• How do they expect to be paid: on completion or in stages? And are they happy for you to retain some of the money until the job has been done to your satisfaction?
• Will they agree to independent arbitration if you end up in a dispute?
• Will they accept a penalty clause for failure to complete the work on time?

Use a builder who is a member of a trade association

Check credentials with the organisation concerned. You can find professional builders and specialists in your area through the Federation of Master Builders (FMB).

FMB members also meet TrustMark’s government-endorsed standards on workmanship and service.

They can offer their clients a ten-year insurance-backed warranty.

Get everything confirmed in writing

• Use a written contract.
• Compile a fully itemised and costed schedule of works.
• Agree a completion date.

The JCT Building Contracts for Home Owners/Occupiers are suitable for domestic building projects in England and Wales. An RICS professional can assist, too, as an independent third party to manage the contract and assist in the event of a dispute.

The FMB provides a plain English contract for use by its members, which sets out the agreed work in layperson’s terms. However, it does not allow third-party assistance, so only choose this if you’re confident managing contracts yourself.

The equivalent contract in Scotland is published by the Scottish Building Contract Committee (SBCC).

Agree ‘start’ and ‘completion’ dates

These can be used as a basis for any bonuses, penalties or changes.

Agree a method for making changes to the work

Agree this before the work begins, in terms of agreeing:

• how to make a change and
• what the time and cost implications will be.

Changes made after the work starts are usually very expensive. Try to avoid this if possible.

Hold back a sum of 5%

This will be released on satisfactory completion of the works.

Make sure the builder has a good waste-disposal strategy

This will help avoid disputes with neighbours when building work is underway.

Make sure the builder has insurance

Obtain details of insurance cover that your prospective builder has in place, including public liability insurance. It is perfectly acceptable to request a copy of their insurance certificate in order to check elements, including the level of cover and policy-renewal date.

Inform your building insurers

Make sure your insurance company and mortgage company are aware of the work being done – you may need a joint policy with the builder.

Make sure the building will be safe at all times for you and your family if staying in occupation during the works.

Don’t automatically accept the cheapest quote

Good builders are hard to find and are always busy. It will be worth the wait.

Don’t pay cash in advance

This is usually on the promise of a ‘cheap’ deal, and could end very badly.

Remember VAT

Unless it’s a new-build house, VAT will be applicable, so budget accordingly.